Environmental ‘loopholes’ and fish population dynamics: comparative pattern recognition with focus on El Niño effects in the Pacific

Abstract

A process of comparative pattern recognition is undertaken for the purpose of garnering insights into the mechanisms underlying some currently puzzling conundrums in fishery resource ecology. These include (a) out‐of‐phase oscillations between anchovies and sardines, (b) the remarkable fish productivity of the Peru–Humboldt marine ecosystem, (c) sardine population increases in the eastern Pacific during El Niños, (d) basin‐wide synchronies in large‐amplitude abundance variations, (e) characteristic spawning of large tuna species in poorly productive areas, (f) contrary trends in Pacific tropical tuna abundance during the 1970s and early 1980s. It is found that each of the items appears to become less enigmatic when the conceptual focus shifts from conventional trophodynamics to the idea that ‘loopholes’ in the fields of biological controls (i.e. of predators of early life stages), produced by poor ocean productivity or by disruptive environmental perturbations, may in fact lead to remarkable reproductive success. Implications include the following: (1) El Niño, rather than being an unmitigated disaster for Peruvian fisheries, may in the long run be a prime reason for the remarkable fishery productivity of the Peru–Humboldt large marine ecosystem. (2) Globally‐teleconnected climatic trends or shifts might produce globally‐coherent population expansions even when local environmental expressions may be quite different. (3) It may be unreasonable to expect any management methodol…