Specific Application of Meso- and Macrocosms for Solving Problems in Fisheries Research

Abstract

The great complexity of open-sea systems has made it necessary to study fish population dynamics, on a small scale, in the laboratory. These indoor studies have given a far better understanding of early life histories of fish species. However, when the results are applied in interpretation of open-sea events, the large gap in structure and scale makes this use of results dubious.

The need for transitional studies to bridge this gap has been suggested since the mid-1970s and increasing numbers of such studies have been carried out, mainly with commercial North Atlantic species. The main results from these studies have questioned the significance of some hypotheses set forward from laboratory observations. These include the hypotheses:

• that larval survival and growth is not dependent upon densities of food organisms in the order of 100 to 1,000 per liter, but rather in the order of 1 to 100;

• that predation might be responsible for a far larger fraction of larval mortality than earlier suggested; and

• that fatal starvation in the sea might be more a question of growth below a species-specific growth barrier for survival rather than larvae brought to a point of irreversible starvation as observed in traditional starvation studies.

Transitional studies are diversifying in the direction of small units (mesocosms) in large number and increasing use of larger systems (macrocosms). A further development should profit from integrated laboratory, meso- and macrocosm studies to deal with more specific and complex questions in early fish population dynamics. This strategy permits studies including post-metamorphosed stages. Larger programs within this field should utilize international coordination and participation, including a number of scientific disciplines.