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Cited by 35Marine and fisheries researchReproductive biology and impacts on aquatic speciesFish Ecology and Management Studies

Spawning Dynamics and Size Related Trends in Reproductive Parameters of Southern Bluefin Tuna, Thunnus maccoyii

Open access
Farley, Jessica. H., Davis, Tim L. O., Bravington, Mark V., Andamari, Retno, Davies, Campbell R.·2015·PLoS ONE
DOI 10.1371/journal.pone.0125744PMC PMC4436339
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Abstract

Knowledge of spawning behaviour and fecundity of fish is important for estimating the reproductive potential of a stock and for constructing appropriate statistical models for assessing sustainable catch levels. Estimates of length-based reproductive parameters are particularly important for determining potential annual fecundity as a function of fish size, but they are often difficult to estimate reliably. Here we provide new information on the reproductive dynamics of southern bluefin tuna (SBT) Thunnus maccoyii through the analysis of fish size and ovary histology collected on the spawning ground in 1993-1995 and 1999-2002. These are used to refine previous parameter estimates of spawning dynamics and investigate size related trends in these parameters. Our results suggest that the small SBT tend to arrive on the spawning ground slightly later and depart earlier in the spawning season relative to large fish. All females were mature and the majority were classed as spawning capable (actively spawning or non-spawning) with a very small proportion classed as regressing. The fraction of females spawning per day decreased with fish size, but once females start a spawning episode, they spawned daily irrespective of size. Mean batch fecundity was estimated directly at 6.5 million oocytes. Analysis of ovary histology and ovary weight data indicated that relative batch fecundity, and the duration of spawning and non-spawning episodes, increased with fish size. These reproductive parameter estimates could be used with estimates of residency time on the spawning ground as a function of fish size (if known) and demographic data for the spawning population to provide a time series of relative annual fecundity for SBT.

AI snapshot

Written from the paper’s full text.

TL;DR

This study uses ovary histology from 1,115 southern bluefin tuna sampled on the spawning ground in 1992–1995 and 1999–2002 to refine reproductive parameters and test size-related trends. It finds that smaller fish arrive later and depart earlier, spawning fraction decreases with size, but once spawning begins females spawn daily, and batch fecundity and spawning/resting episode durations increase with size.

Key findings

  • All 1,115 females were mature; 1,110 were spawning capable and 5 were regressing. Of spawning capable females, 75.3% were actively spawning, 23.9% non-spawning, and 0.8% unknown due to tissue decay. Mean batch fecundity was 6.5 million oocytes.
  • Mean spawning fraction was 0.70, giving a mean spawning interval of 1.4 days; among actively spawning females the fraction was 0.92, giving 1.1 days. By length class, females 150–169 cm, 170–189 cm, and ≥190 cm spawned every 1.3, 1.4, and 1.6 days respectively, but when restricted to spawning females the mean interval was 1.1 days for all fork-length classes.
  • Mean sequential daily spawning duration was 6.25 days; the model predicted 3.6 (SE = 1.4) spawning events for a 150 cm fish and 6.9 (SE = 2.0) for a 190 cm fish, though the length trend was not statistically significant (p > 0.1). Mean sequential resting duration was 1.85 days; predicted resting was 1.3 (SE = 0.1) days at 150 cm and 2.2 (SE = 0.2) days at 190 cm, with a significant length trend (p < 0.01).
  • Relative batch fecundity increased with length: 0.66 at 160 cm, 0.76 at 170 cm, 0.88 at 180 cm, and 1.00 at 190 cm. The indirect method estimated that about 42% of hydrated ovary weight is lost per spawning event (β − α = 0.35, SE = 0.05).

Methods

  • The study combined 640 southern bluefin tuna sampled from the Indonesian longline fishery on the spawning ground in 1999–2002 with 475 individuals from an earlier study, yielding 1,115 ovaries. Fork length, eviscerated body weight, ovary weight, gonad index, and relative condition factor were measured.
  • Ovaries were fixed, sectioned, and histologically classified by the most advanced group of oocytes, postovulatory follicle stage, and atresia level into spawning capable (non-spawning or actively spawning) and regressing phases. Spawning frequency was estimated using the postovulatory follicle method.
  • Batch fecundity was directly estimated by counting hydrated oocytes in 36 ovaries. An indirect Gamma GLM compared ovary weight before versus after spawning, and binomial GLMs estimated the proportion of first-day spawners and first-day resters as functions of fish length. ANOVA tested differences in fork length, gonad index, and relative condition factor among spawning conditions and months.

Limitations

  • Stated: direct batch fecundity was highly variable; the slope of log(fecundity) on log(length) was 3.90 with SE = 1.37, and the authors state it was impossible to estimate the relationship with precision. They also state there was insufficient data to examine seasonal and inter-annual differences in fecundity.
  • Stated: no estimates exist for residency time on the spawning ground as a function of fish size, and electronic tagging is recommended. The spawning-duration GLM was not statistically significant (p > 0.1), and the indirect batch-fecundity method assumes a constant proportional ovary-weight increase before spawning independent of length, described as reasonable but not proven.
  • Evident from the text: length information was available for only 65.4% of females from the first study; postovulatory follicle aging assumed SBT resorb POFs at the same rate as tropical tunas; and direct batch-fecundity estimates were limited to 36 ovaries.

Model-written summary. Check it against the paper before relying on it.

Integrity signals

Registry

Crossref · 10.1371/journal.pone.0125744

Cites

32 of 32 references verified0 citation errors · 0 not checkable

Statistics

Nothing to recompute.

Claims the paper makes

19 of 81 cited sources checked · 8 supported · 1 flagged · accuracy not yet measured

  • Premisecitation

    Relationships between reproductive parameters and fish length are particularly difficult to estimate reliably for species where individuals migrate to and from spawning areas at different times during the spawning season.

    “These data are rarely available for highly migratory species, such as tunas, and are particularly difficult to estimate reliably for species where individuals migrate to and from spawning areas at different times during the spawning season [3, 4].”
    Quote in the paperSubstantial claim1 of 2 sources checked
    • cites [3] KM Schaefer, 2001, Tuna: physiology, ecology and evolution

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

    • cites [4] H Murua, 2003, Procedures to estimate fecundity of marine fish species in relation to their reproductive strategy, J Northwest Atl Fish Sci source
  • Premisecitation

    Relationships between reproductive parameters and fish length are rarely available for highly migratory species such as tunas.

    “These data are rarely available for highly migratory species, such as tunas, and are particularly difficult to estimate reliably for species where individuals migrate to and from spawning areas at different times during the spawning season [3, 4].”
    Quote in the paperSubstantial claim1 of 2 sources checked
    • cites [3] KM Schaefer, 2001, Tuna: physiology, ecology and evolution

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

    • cites [4] H Murua, 2003, Procedures to estimate fecundity of marine fish species in relation to their reproductive strategy, J Northwest Atl Fish Sci source

      The Sampling for fecundity and Spawning Fraction sections explain that movement into and out of spawning areas can complicate representative sampling and estimates. The Introduction also relates fecundity to fish size. But the paper does not say that length-related reproductive data are rarely available for highly migratory species such as tunas; no page numbers are available in our copy. (LLM, conf=0.82)

      Experimental — accuracy not yet measured
  • Premisecitation

    Total egg production is considered a more accurate representation of the reproductive potential of a species than spawning stock biomass because it accounts for the size (or age) composition of the spawning population and changes in annual fecundity with fish size/age.

    “Total egg production is considered a more accurate representation of the reproductive potential of a species than spawning stock biomass as the size (or age) composition of the spawning population, and changes in annual fecundity with fish size/age, are taken into account in the former [1, 2].”
    Quote in the paperSubstantial claim2 of 2 sources checked
    • cites [1] CT Marshall, 2003, Developing alternative indices of reproductive potential for use in fisheries management: case studies for stocks spanning an information gradient, J Northwest Atl Fish Sci source
    • cites [2] SK Lowerre-Barbieri, 2011, Emerging issues and methodological advances in fisheries reproductive biology, Mar Coast Fish source
  • Premisecitation

    The spawning stock of southern bluefin tuna has been monitored since the early 1990s through a catch-monitoring program of the Indonesian longline fishery on the spawning ground.

    “The spawning stock of SBT has been monitored since the early 1990s through a catch-monitoring program of the Indonesian longline fishery on the spawning ground [10].”
    Quote in the paperNot a substantial claim1 of 1 sources checked
    • cites [10] TLO Davis, 1995, Southern bluefin tuna in the Indonesian longline fishery: historical development, composition, season, some biological parameters, landing estimation and catch statistics for 1993, Indones Fish Res J source
  • Findingown data

    The majority of female southern bluefin tuna sampled were classed as spawning capable (actively spawning or non-spawning).

    “All females were mature and the majority were classed as spawning capable (actively spawning or non-spawning) with a very small proportion classed as regressing.”
    Quote in the paperNot a substantial claim
  • Classified as probably not a substantial claim. 40
  • May combine two claims. 34
  • The quote only partly states this claim. 2

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Migratory nucleus oocytes are observed as early as 10:30am to 13:00pm in yellowfin tuna and albacore tuna.

    “Migratory nucleus oocytes are observed as early as 10:30am to 13:00pm in tunas such as yellowfin tuna and albacore tuna (T. albacores) [24–26].”
    Quote in the paperNot a substantial claim1 of 3 sources checked
    • cites [24] GR McPherson, 1991, Reproductive biology of yellowfin tuna in the eastern Australian fishing zone, with special reference to the North-western Coral Sea, Aust J Mar Freshwater Res source
    • cites [25] KM Schaefer, 1998, Reproductive biology of yellowfin tuna (<italic>Thunnus albacares</italic>) in the eastern Pacific Ocean, Inter-Amer Trop Tuna Comm Bull
    • cites [26] JH Farley, 2013, Reproductive dynamics and potential annual fecundity of South Pacific albacore tuna (<italic>Thunnus alalunga</italic>), PLoS ONE source

      In Results, under “Time of spawning and POF degeneration,” the earliest reported observation of migratory nucleus oocytes in albacore is 1405 hrs (2:05 pm), later than the claimed 10:30 am–1:00 pm window. The cited paper does not provide a corresponding observation time for yellowfin tuna. (LLM, conf=0.88)

      Checked by a reasoning model — may be wrong.

      Experimental — accuracy not yet measured

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    After reaching maturity at age ~10-12 years, adult southern bluefin tuna undertake annual migrations between feeding grounds and a single spawning ground in the northeastern Indian Ocean.

    “After reaching maturity at age ~10–12 years, adults undertake annual migrations between these feeding grounds and a single spawning ground in the northeastern Indian Ocean [8, 9].”
    Quote in the paperNot a substantial claim1 of 2 sources checked
    • cites [8] JH Farley, 1998, Reproductive dynamics of southern bluefin tuna, <italic>Thunnus maccoyii</italic>, Fish Bull

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

    • cites [9] K Evans, 2012, Reproductive schedules in southern bluefin tuna: Are current assumptions appropriate?, PLoS ONE source

      The Introduction places maturity at approximately 10–12 years and describes migrations from temperate foraging waters to a single identified spawning ground in the northeastern Indian Ocean. But it calls annual spawning an assumption of stock-assessment models, and the Results and Discussion report fish that remained on foraging grounds through a spawning cycle. The source therefore does not support the unqualified claim that adults migrate annually. (LLM, conf=0.89)

      Experimental — accuracy not yet measured

  • Classified as probably not a substantial claim. May combine two claims.

    Premisecitation

    Skipjack, yellowfin, and bigeye tuna spawn in water temperatures above 24°C.

    “all of which spawn in water temperatures above 24°C and resorb their POFs within 24 hours of spawning.”
    Quote in the paperSubstantial claim1 of 5 sources checked
    • cites [17] JR Hunter, 1986, The spawning frequency of skipjack tuna, <italic>Katsuwonus pelamis</italic>, from the south Pacific, Fish Bull
    • cites [18] KM Schaefer, 1996, Spawning time, frequency, and batch fecundity of yellowfin tuna, <italic>Thunnus albacares</italic>, near Clipperton Atoll in the eastern Pacific Ocean, Fish Bull

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

    • cites [19] NJ Brown-Peterson, 2011, A standardized terminology for describing reproductive development in fishes, Mar Coast Fish source

      The Female Reproductive Cycle section discusses spawning and postovulatory follicles, and the References list a study of skipjack tuna spawning frequency. Searches for the three tuna species and a 24°C spawning threshold found no passage in our copy stating that they spawn above 24°C. (LLM, conf=0.76)

      Experimental — accuracy not yet measured
    • cites [20] McPherson GR (1988) Verification of the postovulatory follicle method for establishing the spawning frequency of yellowfin, bigeye and skipjack tuna in the Coral Sea. Qld Dept Prim Ind, Fish Res Branch, Tech Rep FRB 88/9.

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

    • cites [21] H Nikaido, 1991, Spawning time and frequency of bigeye tuna, <italic>Thunnus obesus</italic>, Bull Nat Res Inst Far Seas Fish

  • Classified as probably not a substantial claim. May combine two claims.

    Premisecitation

    Skipjack, yellowfin, and bigeye tuna resorb their POFs within 24 hours of spawning.

    “all of which spawn in water temperatures above 24°C and resorb their POFs within 24 hours of spawning.”
    Quote in the paperSubstantial claim1 of 5 sources checked
    • cites [17] JR Hunter, 1986, The spawning frequency of skipjack tuna, <italic>Katsuwonus pelamis</italic>, from the south Pacific, Fish Bull
    • cites [18] KM Schaefer, 1996, Spawning time, frequency, and batch fecundity of yellowfin tuna, <italic>Thunnus albacares</italic>, near Clipperton Atoll in the eastern Pacific Ocean, Fish Bull

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

    • cites [19] NJ Brown-Peterson, 2011, A standardized terminology for describing reproductive development in fishes, Mar Coast Fish source

      The Female Reproductive Cycle section says POFs degenerate more slowly in colder waters than in warmer waters, which supports a general relationship between temperature and POF persistence. It does not state that skipjack, yellowfin, or bigeye tuna resorb POFs within 24 hours of spawning, or establish the cited 24°C threshold. No page number is available in our copy. (LLM, conf=0.75)

      Experimental — accuracy not yet measured
    • cites [20] McPherson GR (1988) Verification of the postovulatory follicle method for establishing the spawning frequency of yellowfin, bigeye and skipjack tuna in the Coral Sea. Qld Dept Prim Ind, Fish Res Branch, Tech Rep FRB 88/9.

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

    • cites [21] H Nikaido, 1991, Spawning time and frequency of bigeye tuna, <italic>Thunnus obesus</italic>, Bull Nat Res Inst Far Seas Fish

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    A more protracted spawning season for large fish is not uncommon and has been observed in albacore tuna and other serial spawners such as anchovies, sardines, pilchards, cods and mackerels.

    “A more protracted spawning season for large fish is not uncommon and has been observed in albacore tuna [26] and other serial spawners such as anchovies, sardines, pilchards, cods and mackerels (see [30]).”
    Quote in the paperNot a substantial claim2 of 2 sources checked
    • cites [26] JH Farley, 2013, Reproductive dynamics and potential annual fecundity of South Pacific albacore tuna (<italic>Thunnus alalunga</italic>), PLoS ONE source

      The Discussion reports that spawning activity was lower in small, young albacore and says the results are consistent with their having a shorter spawning season on average than larger, older fish. It also says individual spawning-season duration could not be determined directly, so 'has been observed' states the size-related duration difference more firmly than the source does. The other species are attributed to a separate citation [30]. (LLM, conf=0.82)

      Experimental — accuracy not yet measured
    • cites [30] GR Fitzhugh, 2012, Review of size and age dependence in batch spawning: Implications for stock assessment of species exhibiting indeterminate fecundity, Fish Bull

      The Discussion reports that longer spawning duration with increasing size or age was common, and Table 4 (Conclusions; page unavailable) lists anchovies and Atlantic cod among the species showing that pattern. The available passages do not establish the same duration pattern for pilchards or mackerels; their appearances in the references alone do not do so. The separately cited albacore-tuna example is not attributed to this source. (LLM, conf=0.78)

      Experimental — accuracy not yet measured

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    Delays in spawning activity have been identified in aggregating coral reef species in response to inappropriate currents or temperatures but have not been recorded in tuna species.

    “Delays in spawning activity have been identified in aggregating coral reef species in response to inappropriate currents or temperatures [34] but have not been recorded in tuna species.”
    Quote in the paperNot a substantial claim1 of 1 sources checked
    • cites [34] G Sancho, 2000, Environmental influences on the diel timing of spawning in coral reef fishes, Mar Ecol Prog Ser source

      The Discussion reports that reef fish aggregated at a spawning site and delayed spawning until inflowing currents reversed. The paper supports the current-related delay, but the cited passages do not establish delays in response to inappropriate temperatures. The citation is attached to the coral-reef claim, not the subsequent statement about tuna. (LLM, conf=0.88)

      Experimental — accuracy not yet measured

  • The quote only partly states this claim.

    Findingcitation

    The eastern Atlantic bluefin spawning pattern is consistent with our indirect results for SBT.

    “which is consistent with our indirect results for SBT.”
    Quote in the paperNot a substantial claim1 of 1 sources checked
    • cites [43] G Aranda, 2013, Spawning behaviour and post-spawning migration patterns of Atlantic bluefin tuna (<italic>Thunnus thynnus</italic>) ascertained from satellite archival tags, PLoS ONE source

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Similar data are available for eastern Atlantic bluefin tuna that spawn in the Mediterranean Sea between May and July.

    “Similar data are available for eastern Atlantic bluefin tuna that spawn in the Mediterranean Sea between May and July [43].”
    Quote in the paperNot a substantial claim1 of 1 sources checked
    • cites [43] G Aranda, 2013, Spawning behaviour and post-spawning migration patterns of Atlantic bluefin tuna (<italic>Thunnus thynnus</italic>) ascertained from satellite archival tags, PLoS ONE source

  • Classified as probably not a substantial claim.

    Interpretationcitation

    Since the size distribution of the SBT spawning stock is monitored annually, this information could be used in stock assessments to provide a time series of relative annual fecundity which takes into account information on demographic variation in egg production.

    “Since the size distribution of the SBT spawning stock is monitored annually [26], this information could be used in stock assessments to provide a time series of relative annual fecundity which takes into account information on demographic variation in egg production.”
    Quote in the paperSubstantial claim1 of 1 sources checked
    • cites [26] JH Farley, 2013, Reproductive dynamics and potential annual fecundity of South Pacific albacore tuna (<italic>Thunnus alalunga</italic>), PLoS ONE source

      Split into 2 atoms — 0 confirmed, 1 partially supported, 0 disputed, 0 misattributed, 1 unverifiable. Expand the claim to see per-atom verdicts.

      Experimental — accuracy not yet measured

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    During the spawning phase, the average eastern Atlantic bluefin spawned on 80.3% of days, and spawned for 4.5 ± 3.2 consecutive days before resting.

    “The study also suggested that during the spawning phase, the average fish spawned on 80.3% of days, and spawned for 4.5 ± 3.2 consecutive days before ‘resting’ [43]”
    Quote in the paperNot a substantial claim1 of 1 sources checked
    • cites [43] G Aranda, 2013, Spawning behaviour and post-spawning migration patterns of Atlantic bluefin tuna (<italic>Thunnus thynnus</italic>) ascertained from satellite archival tags, PLoS ONE source

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    This level of variability in batch fecundity has been observed for many tuna species including bigeye, yellowfin, albacore, black skipjack and skipjack.

    “This level of variability has been observed for many tuna species including bigeye [21], yellowfin [25], albacore [26], black skipjack Euthynnus lineatus [35] and skipjack [36].”
    Quote in the paperNot a substantial claim1 of 3 sources checked
    • cites [21] H Nikaido, 1991, Spawning time and frequency of bigeye tuna, <italic>Thunnus obesus</italic>, Bull Nat Res Inst Far Seas Fish
    • cites [25] KM Schaefer, 1998, Reproductive biology of yellowfin tuna (<italic>Thunnus albacares</italic>) in the eastern Pacific Ocean, Inter-Amer Trop Tuna Comm Bull
    • cites [26] JH Farley, 2013, Reproductive dynamics and potential annual fecundity of South Pacific albacore tuna (<italic>Thunnus alalunga</italic>), PLoS ONE source

  • May combine two claims.

    Premisecitation

    Electronic tagging of 13 bluefin showed that fish remained on the spawning ground around the Balearic Sea for an average of 31 ± 7 days after tagging, and were assumed to be in a spawning phase for an average of 24 ± 4 of those days.

    “Electronic tagging of 13 bluefin showed that fish remained on the spawning ground around the Balearic Sea for an average of 31 ± 7 days after tagging, and were assumed to be in a spawning phase for an average of 24 ± 4 of those days [43].”
    Quote in the paperSubstantial claim1 of 1 sources checked
    • cites [43] G Aranda, 2013, Spawning behaviour and post-spawning migration patterns of Atlantic bluefin tuna (<italic>Thunnus thynnus</italic>) ascertained from satellite archival tags, PLoS ONE source

      Table 3 (Materials and Methods; page unavailable) reports 31.22 ± 7.07 days in the Mediterranean and an estimated spawning-phase duration of 23.90 ± 4.11 days, rounded as claimed. However, those two means exclude four of the 13 tags, and the Discussion says mean time in the Balearic spawning area after tagging was about 25 days—not 31. The claim conflates time in the wider Mediterranean with time on the spawning ground. (LLM, conf=0.90)

      Experimental — accuracy not yet measured

  • May combine two claims.

    Premisecitation

    Substantial deployments of electronic tags on SBT have occurred, but to date tags have not been recovered from fish that have visited and returned from the spawning ground.

    “While there have been substantial deployments of electronic tags on SBT [7, 38, 39], to date tags have not been recovered from fish that have visited and returned from the spawning ground (but see [9, 40, 41]).”
    Quote in the paperSubstantial claim1 of 6 sources checked
    • cites [7] S Bestley, 2010, Predicting feeding success in a migratory predator: integrating telemetry, environment, and modeling techniques, Ecol source
    • cites [38] J Gunn, 2001, Tuna physiology, ecology and evolution. Tuna physiology, ecology and evolution

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

    • cites [39] Basson M, Hobday AJ, Eveson JP, Patterson TA (2012) Spatial interactions among juvenile southern bluefin tuna at the global scale: a large scale archival tag experiment. FRDC Report 2003/002. Available: <ext-link xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="uri" xlink:href="http://www.frdc.com.au/research/final-reports/Pages/default.aspx" xlink:type="simple">www.frdc.com.au/research/final-reports/Pages/default.aspx</ext-link>. Accessed: 2014 May 2.

      Not checked in the free run.

    • cites [9] K Evans, 2012, Reproductive schedules in southern bluefin tuna: Are current assumptions appropriate?, PLoS ONE source

      The Materials and Methods report deployment of 90 electronic tags on southern bluefin tuna, supporting the substantial-deployments portion. The Discussion calls for multi-year movement records, but our copy does not establish that no tags had been recovered from fish after a visit to, and return from, the spawning ground. (LLM, conf=0.83)

      Experimental — accuracy not yet measured
    • cites [40] Itoh T, Kurota H, Takahashi N, Tsuji S (2002) Report of 2001/2002 spawning ground surveys. Report CCSBT-SC/0209/20 prepared for the CCSBT Scientific Committee for the 7th Meeting of the Scientific Committee 9–11 September, Canberra, Australia.

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

    • cites [41] TP Patterson, 2008, Movement and behaviour of large southern bluefin tuna (<italic>Thunnus maccoyii</italic>) in the Australian region determined using pop-up satellite archival tags, Fish Oceanog source

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Findingown data

    Length information was available for 65.4% of females sampled in the first study.

    “The majority of fish sampled were 150–210 cm FL although length information was only available for 65.4% of females sampled in the first study.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    Females 160-179 cm FL were sampled over October to January, with a proportion caught in February to April.

    “Females 160–179 cm FL were sampled over the same four month period, but a proportion were caught in February to April (Fig 2C).”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Findingown data

    The majority of fish sampled were 150-210 cm FL.

    “The majority of fish sampled were 150–210 cm FL although length information was only available for 65.4% of females sampled in the first study.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Findingown data

    Of spawning capable females, 0.8% were unknown due to tissue decay.

    “Of the spawning capable females, 75.3% were actively spawning, 23.9% were non-spawning and 0.8% were unknown due to tissue decay.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    Largest females (≥180 cm FL) were sampled over October to March, with small proportions in August/September and April/May.

    “The largest females (≥180 cm FL) were sampled over a broader 6 month period from October through to March, with a small proportion also caught both prior to (August and September) and after (April and May) the main spawning period (Fig 2D).”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Findingown data

    The study combined 640 females from the current study with 475 individuals from [8], providing a total of 1,115 ovaries.

    “Data obtained for the 640 females sampled in the current study were combined with data from 475 individuals from [8] providing a total of 1,115 ovaries (S1 Table).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [8] JH Farley, 1998, Reproductive dynamics of southern bluefin tuna, <italic>Thunnus maccoyii</italic>, Fish Bull

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  • May combine two claims.

    Findingown data

    The fraction of females spawning per day increased between September (0.37) and January (0.79) and then declined through to April (0.56).

    “The fraction of females spawning per day increased between September (0.37) and January (0.79) and then declined through to April (0.56) (Fig 3).”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    The relative abundance of non-spawning females was highest in September and lowest in January.

    “In contrast, the relative abundance of non-spawning females was highest in September and lowest in January, but comprised a relatively stable fraction (16.8 to 29.4%) in October to April (Fig 3).”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    Overall, mean GI was low in October and then increased until January, before declining in February.

    “Overall, mean GI was low in October and then increased until January, before declining in February.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    For fish of similar lengths, most "before" ovaries were much heavier than "after" ovaries, although there was some overlap in GW between the stages.

    “A comparison of the weight of ovaries of fish that were about to spawn (“before” ovaries) with those that had recently spawned (“after” ovaries) showed that for fish of similar lengths, most “before” ovaries were much heavier than “after ovaries” (Fig 7), although there was some overlap in GW between the stages.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    Kn was highest in November and generally declined towards the end of the spawning season.

    “Kn was highest in November and generally declined towards the end of the spawning season (Fig 5A).”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    The point estimates of slopes on ln-length were about 2.45 before spawning and 2.89 afterwards.

    “The point estimates of slopes on ln-length are very similar (about 2.45 before spawning versus 2.89 afterwards) although the confidence interval on before-spawners is wide because there were only 51 samples available.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    The relative abundance of actively spawning females was lowest at the beginning of the spawning season (September) and highest in the middle of the season (December to February).

    “The relative abundance of actively spawning females was lowest at the beginning of the spawning season (September) and highest in the middle of the season (December to February) (Fig 3).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    There was a trend for increasing spawning duration with fish length, although the GLM was not statistically significant (p > 0.1).

    “There was a trend for increasing spawning duration with fish length, although the GLM was not statistically significant (p > 0.1) (Fig 8A).”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    There is a trend for increasing resting duration with fish length, and the GLM was significant at (p <0.01).

    “There is a trend for increasing resting duration with fish length, and the GLM was significant at (p <0.01) (Fig 8B).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    Batch fecundity was found to increase with fish size in SBT, although it was quite variable making the relationship uncertain.

    “Batch fecundity was found to increase with fish size in SBT, although it was quite variable making the relationship uncertain.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    Estimates of hydrated ovary weight have been measured more often and show less individual variation than direct batch fecundity.

    “The situation is slightly better for estimates of hydrated ovary weight, which have been measured more often and show less individual variation,”
    Quote in the paperSubstantial claim

  • The quote only partly states this claim.

    Premisecitation

    In the 1992-1995 study, all female southern bluefin tuna examined were mature adults capable of spawning.

    “The study collected ovaries from females predominantly between 165 and 195 cm fork length (FL) and found that all were mature adults that were capable of spawning, except for a few regressing fish that had just completed spawning (<1% of females examined).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [8] JH Farley, 1998, Reproductive dynamics of southern bluefin tuna, <italic>Thunnus maccoyii</italic>, Fish Bull

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  • May combine two claims.

    Premisecitation

    Individual southern bluefin tuna departed the spawning ground as soon as spawning was completed, to be replaced by newly arriving fish.

    “The population spawning season was protracted (effectively from September to April) although individuals did not spawn for that entire period and departed as soon as spawning was completed, to be replaced by newly arriving fish [8].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [8] JH Farley, 1998, Reproductive dynamics of southern bluefin tuna, <italic>Thunnus maccoyii</italic>, Fish Bull

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductown data

    Regressing fish were rarely encountered (only five during both studies).

    “regressing fish were rarely encountered (only five during both studies) and were not included in the calculation.”
    Quote in the paperNot a substantial claim

  • Classified as probably not a substantial claim.

    Study design and conductreasoning

    Fish with advanced yolked oocytes and new or <12 hour POF were excluded because it was unknown whether they would develop a new batch within 12-24 hours.

    “Fish with advanced yolked oocytes and new or <12 hour POF were not included in the analysis because it was unknown whether these fish would develop a new batch of oocytes within the following 12–24 hours.”
    Quote in the paperSubstantial claim

  • Classified as probably not a substantial claim. May combine two claims.

    Study design and conductreasoning

    Ovaries selected for batch fecundity contained hydrated oocytes but no new POFs to exclude partial spawning.

    “ovaries were selected that contained hydrated oocytes but did not have new POFs, which would indicate partial spawning of the batch.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Premisecitation

    The Indonesian catch-monitoring program detected changes in the size and age composition of fish caught in the early 2000s, with the abundance of small/young fish increasing relative to large/old fish.

    “The program detected changes in the size and age composition of fish caught in the early 2000s; the abundance of small/young fish increased relative to large/old fish [11].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [11] Farley J, Nugraha B, Proctor C (2012) Update on the length and age distribution of SBT in the Indonesian longline catch. Report CCSBT-ESC/1208/25 prepared for the CCSBT Extended Scientific Committee for the 17th Meeting of the Scientific Committee, 27–31 August 2012, Tokyo, Japan.

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  • Classified as probably not a substantial claim.

    Premisecitation

    Water temperature appears to be the dominant factor governing POF resorption rates.

    “as water temperature appears to be the dominant factor governing resorption rates [22].”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [22] GR Fitzhugh, 1995, Temperature influence on postovulatory follicle degeneration in Atlantic menhaden, <italic>Brevoortia tryannus</italic>, Fish Bull

  • Classified as probably not a substantial claim. May combine two claims.

    Premisecitation

    Questions remained regarding the duration of spawning and non-spawning episodes, and annual residency time on the spawning ground for southern bluefin tuna.

    “Farley and Davis [8] provided the first quantitative understanding of the dynamics of spawning of SBT; however, questions remained regarding the duration of spawning and non-spawning episodes, and annual residency time on the spawning ground.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [8] JH Farley, 1998, Reproductive dynamics of southern bluefin tuna, <italic>Thunnus maccoyii</italic>, Fish Bull

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  • Classified as probably not a substantial claim. May combine two claims.

    Interpretationreasoning

    Smaller southern bluefin tuna that appear on the spawning ground are in the process of recruiting into the spawning population and are likely to provide influential data on the relationship between fish size and egg production.

    “It is these fish that are in the process of recruiting into the spawning population and are likely to provide influential data on the relationship between fish size and egg production.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Premisecitation

    Southern bluefin tuna is considered to be overfished and the spawning stock is at historically low levels following substantial fishing pressure since the 1950s.

    “Monitoring the SBT spawning stock was imperative as the species is considered to be overfished and the spawning stock is at historically low levels [12, 13] following substantial fishing pressure since the 1950s.”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites [12] CCSBT (2011) Report of the sixteenth meeting of the Scientific Committee. Commission for the Conservation of Southern Bluefin Tuna, 10–13 October, Bali, Indonesia. Available: <ext-link xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="uri" xlink:href="http://www.ccsbt.org/site/reports_past_meetings.php" xlink:type="simple">www.ccsbt.org/site/reports_past_meetings.php</ext-link>. Accessed: 2014 May 2.

      Not checked in the free run.

    • cites [13] Hillary RM, Preece A, Davies C, Barnes B, Begg G (2011) Reconditioning of the southern bluefin tuna operating model: exploratory data analysis, fitting performance, and current stock status. Report CCSBT-ESC/1107/11 prepared for the CCSBT Extended Scientific Committee for the 16th Meeting of the Scientific Committee 19–28 July, Bali, Indonesia.

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Ovarian follicular atresia prior to spawning has been documented in several species.

    “Ovarian follicular atresia prior to spawning has been documented in several species [33]”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [33] PJ Bromley, 2000, The influence of feeding regime on sexual maturation, fecundity and atresia in first-time spawning turbot, J Fish Bio source

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Atresia of yolked oocytes can occur any time in species with asynchronous oocyte development.

    “Atresia of yolked oocytes can occur any time in species with asynchronous oocyte development [31]”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [31] DA Pavlov, 2009, Fish reproductive biology, implications for assessment and management source

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based). May combine two claims.

    Interpretationnone given

    Large SBT may have faster swimming speeds and can cover the migration routes from the Southern Ocean in a shorter time compared to smaller fish.

    “Large SBT may have faster swimming speeds and can cover the migration routes from the Southern Ocean in a shorter time compared to smaller fish.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductown data

    The confidence interval on before-spawners is wide because there were only 51 samples available.

    “The point estimates of slopes on ln-length are very similar (about 2.45 before spawning versus 2.89 afterwards) although the confidence interval on before-spawners is wide because there were only 51 samples available.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    The arrival of large fish before smaller fish in spawning areas has been documented in several pelagic and non-pelagic fish species, including Atlantic bluefin tuna, and has been linked to size-related differences in migration, maturation and temperature preferences.

    “The arrival of large fish before smaller fish in spawning areas has been documented in several pelagic and non-pelagic fish species, including Atlantic bluefin tuna (T. thynnus), and has been linked to size-related differences in migration, maturation and temperature preferences [28, 29].”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites [28] F Vandeperre, 2007, Do bigger fish arrive and spawn at the spawning grounds before smaller fish: Cod (Gadus morhua) predation on beach spawning capelin (Mallotus villosus) from coastal Newfoundland, Est Coast Shelf Sci source
    • cites [29] MJ Schirripa, 2011, A literature review of Altantic bluefin tuna age at maturity, ICCAT Coll Vol Sci Pap

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  • May combine two claims.

    Interpretationcitation

    Females may delay spawning to allow time to recover from the spawning migration and/or acclimate to the quite different environmental conditions.

    “Once on the spawning ground, females may delay spawning to allow time to recover from the spawning migration [8] and, or, acclimate to the quite different environmental conditions.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [8] JH Farley, 1998, Reproductive dynamics of southern bluefin tuna, <italic>Thunnus maccoyii</italic>, Fish Bull

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Atresia may be a mechanism for fish to reallocate energy from the gonads during unfavourable conditions.

    “and may be a mechanism for fish to reallocate energy from the gonads during unfavourable conditions [32].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [32] W Van Winkle, 1995, Early life history and recruitment in fish populations

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  • May combine two claims.

    Premisecitation

    SBT arrive on the spawning ground in this condition or just recovering from it.

    “They concluded that SBT arrive on the spawning ground in this condition or just recovering from it.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [8] JH Farley, 1998, Reproductive dynamics of southern bluefin tuna, <italic>Thunnus maccoyii</italic>, Fish Bull

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Very few estimates of potential annual fecundity are available for tuna.

    “Very few estimates of potential annual fecundity are available for tuna [3].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [3] KM Schaefer, 2001, Tuna: physiology, ecology and evolution

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Interpretationreasoning

    Non-spawners could also be in resting phases between spawning episodes during the season.

    “However, non-spawners could also be in a resting phases between spawning episodes during the season.”
    Quote in the paperNot a substantial claim

  • Classified as probably not a substantial claim.

    Premisecitation

    Schaefer [3] considered that for most species of tuna the reported fecundity estimates were probably inadequate to estimate annual fecundity.

    “Because of the high variability in batch fecundity, Schaefer [3] considered that for most species of tuna the reported fecundity estimates were probably inadequate to estimate annual fecundity.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [3] KM Schaefer, 2001, Tuna: physiology, ecology and evolution

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  • Classified as probably not a substantial claim.

    Interpretationnone given

    There is no obvious way of estimating duration on the spawning ground in the absence of position data from electronic tags.

    “Unfortunately, there is no obvious way of estimating duration on the spawning ground in the absence of position data from electronic tags.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Interpretationnone given

    Individual residency time on the spawning ground remains unknown.

    “but individual residency time on the spawning ground remains unknown.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    The predicted batch fecundity of a 125 cm yellowfin tuna varied from 1.454 million eggs in one year to 2.495 million eggs in the next.

    “The predicted batch fecundity of a 125 cm fish was reported to vary from 1.454 million eggs in one year to 2.495 million eggs in the next.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [25] KM Schaefer, 1998, Reproductive biology of yellowfin tuna (<italic>Thunnus albacares</italic>) in the eastern Pacific Ocean, Inter-Amer Trop Tuna Comm Bull

  • May combine two claims.

    Premisecitation

    Three mature Atlantic bluefin tuna (207-268 curved FL) remained on the spawning ground in the Gulf of Mexico for an average of 39 ± 11 days and were in an assumed spawning phase for an average of 18 ± 7 days.

    “Electronic tagging data showed that three mature Atlantic bluefin tuna (207–268 curved FL) remained on the spawning ground in the Gulf of Mexico for an average of 39 ± 11 days and were in an assumed spawning phase for an average of 18 ± 7 days [42].”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [42] SLH Teo, 2007, Annual migrations, diving behavior, and thermal biology of Atlantic bluefin tuna, <italic>Thunnus thynnus</italic>, on their Gulf of Mexico breeding grounds, Mar Biol source

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Interpretationreasoning

    The slightly lower spawning fraction in larger SBT may be due to these fish spending more time in a pre-spawning condition when first arriving in the spawning ground, or resting longer between spawning episodes, compared to smaller fish.

    “For larger SBT, the slightly lower spawning fraction is difficult to explain but may be due to these fish spending more time in a pre-spawning condition when first arriving in the spawning ground, or resting longer between spawning episodes, compared to smaller fish.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Hunter et al. [37] found a two-fold variation in batch fecundity of the northern anchovy Engraulis mordax between years.

    “Hunter et al. [37] found a two-fold variation in batch fecundity of the well-studied northern anchovy Engraulis mordax between years.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [37] Hunter JR, Lo NCH, Leong RJH (1985) Batch fecundity in multiple spawning fishes. In: Lasker T, editor. An egg production method for estimating spawning biomass of pelagic fish: application to the northern anchovy, <italic>Engraulis mordax</italic>. US Dept Commerce, NOAA Tech Rep NMFS 36. pp. 67–77.

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Interpretationcitation

    Likely factors contributing to batch fecundity variability include geographical variation, inter-annual variation, fish condition, and stage of the spawning cycle-some of which may be interrelated.

    “Likely factors contributing to this variability include geographical variation, inter-annual variation, fish condition, and stage of the spawning cycle—some of which may be interrelated.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Schaefer [25] reported both geographical and inter-annual variation in batch fecundity of yellowfin tuna.

    “Schaefer [25] reported both geographical and inter-annual variation in batch fecundity of yellowfin tuna.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [25] KM Schaefer, 1998, Reproductive biology of yellowfin tuna (<italic>Thunnus albacares</italic>) in the eastern Pacific Ocean, Inter-Amer Trop Tuna Comm Bull

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Interpretationcitation

    The relatively short average duration on the spawning ground suggests a possible preliminary entry phase and then an average of two series of consecutive daily spawning cycles.

    “The relatively short (average) duration on the spawning ground would suggest a possible preliminary entry phase and then an average of two series of consecutive daily spawning cycles,”
    Quote in the paperNot a substantial claim
    • The authors state this as an assumption: The number of consecutive daily spawning/non-spawning events for Atlantic bluefin tuna is similar to that of the largest SBT in this study.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Interpretationnone given

    The total number of spawning cycles is still unknown for SBT.

    “Although the average duration of both parts of the spawning cycle (spawning and non-spawning) as a function of fish size is known, the total number of cycles is still unknown for SBT.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Interpretationnone given

    Spawning may cease temporarily if conditions such as food availability or water temperatures deteriorate, or to allow fish to recover temporally from periods of consecutive daily spawning.

    “Spawning may cease temporarily if conditions such as food availability or water temperatures deteriorate, or to allow fish to recover temporally from periods of consecutive daily spawning.”
    Quote in the paperNot a substantial claim

  • Classified as probably not a substantial claim.

    Interpretationreasoning

    The product of relative batch fecundity and relative number of spawning events per spawning season would provide an estimate of relative annual fecundity as a function of fish size.

    “The product of relative batch fecundity and relative number of spawning events per spawning season (if known) would provide an estimate of relative annual fecundity as a function of fish size.”
    Quote in the paperSubstantial claim
63 of 63

  • The paper relies on this without support.

    Knowledge of spawning behaviour and fecundity of fish is important for estimating the reproductive potential of a stock and for constructing appropriate statistical models for assessing sustainable catch levels.

    “Knowledge of spawning behaviour and fecundity of fish is important for estimating the reproductive potential of a stock and for constructing appropriate statistical models for assessing sustainable catch levels.”

  • The paper relies on this without support.

    Estimates of length-based reproductive parameters are particularly important for determining potential annual fecundity as a function of fish size, but they are often difficult to estimate reliably.

    “Estimates of length-based reproductive parameters are particularly important for determining potential annual fecundity as a function of fish size, but they are often difficult to estimate reliably.”

  • The paper relies on this without support.

    An understanding of the relationships between reproductive parameters, such as spawning frequency, batch fecundity and spawning duration, with fish length is required to estimate potential annual fecundity at size for a multiple-spawning species with indeterminate fecundity.

    “An understanding of the relationships between reproductive parameters, such as spawning frequency, batch fecundity and spawning duration, with fish length are required to estimate potential annual fecundity at size for a multiple-spawning species with indeterminate fecundity.”

  • The authors state this as an assumption.

    SBT resorb POFs at the same rate as other tropical spawning tuna.

    “It was assumed that SBT resorb POFs at the same rate as other tropical spawning tuna as water temperature appears to be the dominant factor governing resorption rates [22].”

  • The authors state this as an assumption.

    POFs remain visible for only 24 hours in SBT ovaries.

    “This method uses the incidence of mature females with POFs (assumed to remain visible for only 24 hours in SBT ovaries) to estimate the fraction of the population spawning per day (spawning fraction) and spawning frequency (inverse of spawning fraction).”

  • The paper relies on this without support.

    Fish with migratory nucleus oocytes indicate imminent hydration and spawning.

    “Fish with migratory nucleus oocytes indicate imminent hydration and spawning.”

  • The paper relies on this without support.

    POFs are unlikely to remain in ovaries of fish with hydrated oocytes by that stage of the daily cycle.

    “Fish with hydrated oocytes were not included in the analysis because by that stage of the daily cycle, it is unlikely that POFs would still remain in the ovaries.”

  • The authors state this as an assumption.

    GW increases by a constant proportion just before spawning, independent of fish length.

    “On this evidence and a priori grounds, it is reasonable (but not proven) to assume that GW increases by a constant proportion just before spawning, independent of fish length.”

  • The paper relies on this without support.

    The proportion of females not spawning on a given day can be used to estimate the mean number of sequential daily spawning events (mean = 1/proportion).

    “the proportion of females sampled that did not spawn the day before capture (n = 40) was 0.16, providing a mean number of sequential daily spawning events for SBT at 6.25 days.”

  • The paper relies on this without support.

    The proportion of females that had just finished spawning can be used to estimate the mean number of sequential resting days (mean = 1/proportion).

    “the proportion of females sampled that had just finished spawning (n = 311) was 0.54, providing a mean number of sequential resting days of 1.85.”

  • The authors state this as an assumption.

    The number of consecutive daily spawning/non-spawning events for Atlantic bluefin tuna is similar to that of the largest SBT in this study.

    “assuming that the number of consecutive daily spawning/non-spawning events was similar to that of the largest SBT in this study.”
11 of 11

Self-check

Percentages, sums and reported differences re-computed from the paper’s own numbers.

Each contradiction between two passages listed here was confirmed by an independent check.

  • Spawning fraction is reported in days

    Minor

    The paper distinguishes the dimensionless spawning fraction from the spawning interval measured in days, but later calls 1.1 days a spawning fraction.

  • Conflicting counts of before-spawning ovaries

    Minor

    The results state that only 51 before-spawning samples were available, but the Fig 7 caption reports 52 before-spawning ovaries.

2 of 2

Cites

Flagged first, then by citations

1 of the 33 references couldn’t be matched to a known paper.

Research works printed but not linked: 6

  1. JH Farley, 1998, Reproductive dynamics of southern bluefin tuna, <italic>Thunnus maccoyii</italic>, Fish Bull, 96, 223
  2. JR Hunter, 1980, Spawning incidence and batch fecundity in northern anchovy, <italic>Engraulis mordax</italic>, Fish Bull, 77, 641
  3. JR Hunter, 1980, Sexual maturity, batch fecundity, spawning frequency, and temporal pattern of spawning for the northern anchovy, <italic>Engraulis mordax</italic>, during the 1979 spawning season, Calif Coop Oceanic Fish Invest Rep, 21, 139
  4. KM Schaefer, 1996, Spawning time, frequency, and batch fecundity of yellowfin tuna, <italic>Thunnus albacares</italic>, near Clipperton Atoll in the eastern Pacific Ocean, Fish Bull, 94, 98
  5. MJ Schirripa, 2011, A literature review of Altantic bluefin tuna age at maturity, ICCAT Coll Vol Sci Pap, 66, 898
  6. Goldberg SR, Au DWK (1986) The spawning of skipjack tuna from southeastern Brazil as determined from histological examinations of ovaries. In: Symons PEK, Miyake PM, Sakagawa GT, editors. Proceedings of the ICCAT Conference on the International Skipjack Year Program. Madrid: ICCAT. pp 277–284.

Cited by

Sorted by citations

Related

Authors
Farley, J. H., Davis, T. L. O., Bravington, M. V., Andamari, R., & Davies, C. R.
Corresponding author
Farley, Jessica. H.
Venue
PLoS ONE
Publisher
Public Library of Science (PLoS)
Published
2015-05-18
Volume
10
Issue
5
Pages
e0125744
ISSN
1932-6203 (ISSN-L)
DOI
10.1371/journal.pone.0125744
PMC
PMC4436339
OpenAlex
W2285226297
Cited by
35
References
33
Citations by year
2026: 4 · 2025: 3 · 2024: 3 · 2023: 3 · 2022: 1 · 2021: 6 · 2020: 2 · 2019: 2 · 2018: 2 · 2017: 2 · 2016: 2 · 2015: 2 · 2014: 3
FWCI
2.15
Type
journal article
Language
en
Open access
Licence
Locations
  • PLoS ONE (publishedVersion, cc-by)
  • PubMed (publishedVersion)
  • Europe PMC (PubMed Central) (submittedVersion, cc-by)
  • PubMed Central (submittedVersion, cc-by)
  • DOAJ (DOAJ: Directory of Open Access Journals) (submittedVersion, cc-by-sa)
Funders
  • Commonwealth Scientific and Industrial Research Organisation
  • Fisheries Research and Development Corporation
Topics
  • Physical Sciences › Environmental Science › Global and Planetary Change › Marine and fisheries research
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Physiology › Reproductive biology and impacts on aquatic species
  • Physical Sciences › Environmental Science › Nature and Landscape Conservation › Fish Ecology and Management Studies
Keywords
southern bluefin tuna, Thunnus maccoyii, spawning dynamics, batch fecundity, ovarian histology, annual fecundity, female maturity
MeSH terms
Animals, Female, Fertility, Fisheries, Indonesia, Organ Size, Ovary, Reproduction, Seasons, Tuna, Body Size

About these checks

Registry, retraction, Cites and statistics results are computed, not judged, with one exception: a printed reference that no index lists is read once by a model before it counts as a citation error. Claims are extracted by a model and kept only when their quote appears verbatim in the text; each cited source is then checked, with a model’s help, for whether it says what the claim relies on. Those verdicts can be wrong — read the claim’s quote and the cited source before relying on one.

Claims read by deepseek-v4.1-flash under definition version 3 (extract-v3) on 2026-10-16.

Classified by jev-1.13-20260917 (gold-guideline-v0.2) on 2026-10-16.

Cited sources are checked by gpt-6-sol.

Statistics and arithmetic are recomputed, not judged.

Confidence bands are shown only for fields calibrated on our annotated test set. None is calibrated yet, so no band is shown.

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