Comparative Modeling of Two Especial Scenarios of Bioresources Collapses: Canadian Atlantic Cod and Caspian Sea Sturgeon

摘要

Article discusses the modeling of the aspects of two situations of rapid depletion of numerous in the past fish populations in the early 1990s: Atlantic cod near the coast of Canada and sturgeons in the Caspian Sea. Since the collapse, both overfished populations for more than a quarter of a century, contrary to expectations, have not restored the precollapse fishing stock, despite the restrictive measures and fish-breeding measures of salvation. In the dynamics of two populations with different spawning ecology, it is underlined the identical features leading to a sudden sharp decrease of the efficiency of reproduction of fish. A computational model of stock replenishment based on the formalization of various factors of juvenile survival in early ontogeny was developed. The explanation offered in the article for the appearance of a very complex form of dependence for the marine active predator-cannibal of cod Gadus morhua and the sturgeon Acipenser gueldenstaedtii breeding in the Volga River is different. In the iterative representation, this reproductive efficiency model will determine two different-quality regimes in the dynamics of populations. It was possible to simulate a scenario for an operational strategy, when, after a maximum of catches, the basic equilibrium for the environment of a population is sharply reduced and a pseudostochastic regime of oscillations arises. In the case of continued fishing, the alternative limited chaotic set also loses its asymptotic stability, which will describe a sudden transition to the degradation of fish stocks through the phase of relaxation fluctuations that have been observed in the Newfoundland cod fishery immediately prior to the moratorium established in 1992.