harvest are profound. During the predevelopment and growth phases of many of the early industrial fisheries in the early 20th century the promise of unlimited yield was fulfilled and supported the idea that biological productivity surpassed its exploitation. In contrast to the current state of industrial fishing, these fisheries (which include such stocks as north Atlantic cod, herring, and whales) were much different than those in existence today. They were not overcapitalized, hence fish abundance was sustainable relative to fishing effort. Additionally, fishermen were not specialists to the extent that they made their livelihood
on single stock, so when fish abundances varied as a result of natural environmental fluctuations fishers were able to target better performing stocks. Fishing activities at this time did not exploit the stock in their complete geographic range and thus there was a spatial refuge for fish to compensate for harvest. Finally, growth overfishing masked apparent depletions as did the effects of serial depletions of similar stocks. Fishing technology was also limited at this time (no global positioning systems, no ability to exploit the deep sea) and although the age of sail was beginning to wane, fishing methods
were not advanced. The recognition that industrial fishing was affecting the abundance of stocks was only recognized during its absence: during World Wars I and II major naval engagements of the war occurred in the eastern North and fishing activity was suspended. After the conclusion of these wars, fishermen found that the fish had greatly increased in abundance (Hilborn et al 2003). Fishing activity, and major crashes, starting in the 1970s indicated that the stocks were susceptible to overexploitation and previous ideas of that fish stocks were limitless were catastrophically flawed.
Two major fishery crashes, that of the Peruvian anchoveta fishery and the Newfoundland cod indicated the complexity of interactions among fishers, fish populations, and the environment that were not correctly assessed. In the case of the Peruvian anchoveta fishery, ecosystem changes that resulted from El Nino conditions (warming) altered the spawning behavior and spawning capacity of the stock. Overly optimistic limits resulted in excessive fishing mortality on the spawning stock during the El Nino regime shift. At this time the size of the stock was exceedingly small due to
overfishing and environmental conditions for reproduction were far from optimal (Clark 1977). The second major collapse that occurred was that of north Atlantic cod (by 1992 they were commercially extinct) the aggressive overcapitalization subsidized by the Canadian government, reinforced by optimistic estimates of yield, resulted in severe overfishing of the stock. Because of the tight control of shellfish resources in the same area fishers had to be cod specialists and were excluded from diversifying their target species the crash of the single species had a profound impact on the social system and
economic welfare of all of the participants of the fishery (Hillborn et al 2003). These stock collapses necessitated a more realistic view of fishery management and the effects of fishing on marine populations. The extent to which commercial fishing impacted stocks and the extent to which the worlds fish populations were in peril was not well understood. As a fisheries biologist Pauly has made a substantial contribution to understanding the effects of fishing, and taking the a global view of the state of fisheries by documenting the status and trends of fisheries around the world.
He has written a number of books and articles for the lay person and has described the ecosystem effects of fishing coining the term fishing down the food web (Pauly et al 1998). This phenomenon is the description of how fishers, have been forced, because of reduced abundances, to target fish at low trophic levels. In a limitless ocean fishers would not be forced to harvest small fish species of reduced market value. Other profound changes in fish stocks have been reported because of harvest: the reduction of genetic diversity (Hauser et al. 2002). Hauser et al. , in an analysis of snapper
populations in New Zealand, found that the amount of micro-satellite diversity was reduced. Genetic diversity within a species is the sum total of information in the genes of individual organisms of a species. Though this type of genetic diversity is not related to the fitness of an individual its ability to reproduce successfully, the maintenance of such diversity is necessary for biological populations to adapt to changes in the environment. This could be especially important as the ocean environment changes due to alterations of biota (due to anthropogenic disturbance) and physical conditions (by global warming for
example). Genetic effects have only begun to be realized; much of the evidence for genetic changes in fish stocks is based on life history characters, such as growth rate, size at age, and size or age at first maturity and these changes can have important effects on fishery yield. The realization that fish stocks are vulnerable to overfishing has lead to many changes in their evaluation and management. For example, it is now recognized that management measures must be changed from the previously used simplistic models that only evaluate one species at a time to more sophisticated models. New management
models such as ecosystem based models will incorporate multiple species and the environmental conditions of the ocean for better prediction. Alternatively, some workers have highlighted the need to address the inherent social, economic, and biological complexity is one aspect of the future work in fishery science. However, in many ways this approach does not necessarily require quantitative approaches and in fact may lead to simpler model formulations. Fishery management and conservationists will be challenged with maintaining the economic expectations of fishers and the need to restore stocks and ecosystems.
This approach will require and understanding of the economics of fishing and how best to focus our limited research resources to maximize the efficacy of management. This management will have to be adaptive and we will need to be very aware of the implications of neglecting fishery trends over short time periods. W. G. Clark. 1977. The lessons of the Peruvian anchoveta fishery. California Cooperative Oceanic Fisheries Investigations Reports 19: 57-63. Hauser, L. , G. J. Adocock, P. J. Smith, J. H. Bernal-Ramirez, and G. R. Carvahlo. 2002. Loss of microsatellite diversity and low effective population size in an
overexploited population of New Zealand snapper (Pagrus auratus). Proceedings of the National Academy of Science 99:11742-11747. Hilborn, R. 2004. Ecosystem-based fisheries management: the carrot or the stick? Perspectives on eco-system-based approaches to the management of marine resources. Marine ecology Progress Series 274:275-278. Huxley, T. H. 1883. Inaugural address. Pages 1-22 in The Fisheries Exhibition Literature. International Fisheries Exhibition, London. Pauly, D. , V. Christensen, J. Dalsgaard, R. Froese and F. C. Torres. 1998. Fishing down marine food webs. Science 279: 860-863.