The Impact of Overfishing on Biodiversity
Overfishing is described as capturing more fish than the population can replace by natural reproduction, resulting in total depletion. Many animals are being driven to extinction as a result of human impact on the climate. Because of the high demand for larger fish, the stock of fish is decreasing dramatically, as is their average size. Members of populations have a tendency to demand big fish, which causes them to be depleted, resulting in a reduction in biodiversity. Large-scale selective harvesting has resulted in a genetic trade-off in order to accelerate reproduction. The constant demand for the biggest fish together with the adaptive response of the fish for a smaller body size will, in the end, lead to the extinction of the fitter individual. There has been documentation in several cases all over the world within the Atlantic cod populations, the Grand Banks code, and the Atlantic silverside that touch on fishing. The impacts that are being exhibited by fisheries on the aquatic community show how greatly humans are affecting the environment.
High Mortality Rates and Unsustainable Fishing Practices
Overfishing is resulting in high extrinsic mortality rate on the fish populations, which leads to significant declines in the fish numbers. A report by the United Nations Food and Agriculture Organization shows that 74% of the world's fish stocks is being fished at levels above sustainable yield which exceeds the largest catch that is supported by a species to stock over a given time (Helfman p.220). All efforts that have been put to address these issues, like only fishing the larger ones that are matured so as to allow the stocks to recover and reproduce, have failed to address the effects of fishing on populations. The collapse of Atlantic cod fishery is a well-documented case of the anthropogenic impacts of fishing that take place whereby large size selective harvests of fish led to significant evolutionary changes in cod populations. This particular high demand for large fish developed a disturbance in the trophic level stability which is explained as fishing down the food chain (Bard p.486). Statistics by the UNFAO global fisheries showed that from 1954 to 1994, the mean trophic level of fish harvests had declined (Kuparinen p.656). This decrease denoted that there was a tradeoff from large, long-living fish to smaller, short-living fish (Conover p.95). The type of fishing methods of selective large-harvest fishing significantly influenced this impact.
Evolutionary Consequences of Overfishing
Early maturation is also a repercussion for small-sized individuals since the probability of death at a previous stage in life was high (Hutchings p.294). The smaller size and earlier maturity increased the likelihood of survival and reproduction of an individual. The future progeny inherits the genes of surviving to reproduce. In 1992, a moratorium was declared on the Northern Cod fishery. Only one percent of biomass remained demanding the end of a 500-year fishing fleet with the Atlantic cod (Helfman p.305). The fishing mortality rates were very high that it was not allowing stock restoration. The evolution impacts of the massive selection pressure have become long-lasting. The size of the cod today had significantly become smaller than before in 1950. If the genetic variability is lost, it may lead to the extinction of that gene for a larger size. According to the analysis of the collapse, the main reason for its decline was because of overfishing (Hilborn p.35). The second reason was the dependence for the fishery maintaining itself on the nutrient cycle. The following are the factors that contributed to the collapse of the cod fishery;
Technological Progress
Introduction and proliferation of technology that led to the increase of the volume of landed fish played a significant role that depleted the cod stocks off the shores of Newfoundland. For many years, the local fishermen made use of technology that limited the volume they could fish. The area they caught in, and it also gave them the freedom to choose specific species and ages of fish. New technologies were introduced in 1950 that enabled the fishermen to increase their volume of a catch by fishing in larger areas, deeper depths, and for prolonged times. The northern cod population was adversely affected by the new technologies in two ways. The first way was by increasing the area and depth of fishing areas as the cods were being depleted, thus making the surviving fish unable to replenish the stock that is lost each year. The second way was that the trawlers are catching significant amounts of fish that were economically unimportant yet it was imperative ecologically. For instance, in the northern cod, a high number of capelin (a prey species) was insignificant for the cod which undermined the possible survival of the cod stock that was remaining (Myers p.283).
Ecological Ignorance
Another significant reason that led to the collapse of the fishery is the uncertainty in determining the cod as a resource. When the information about a resource is limited managing, it becomes tight. Managing of fishing involves a high degree of uncertainty because problems that crop like the resources (Heithaus p.205). The Newfoundland's cod fisheries did not have an exception with the incomplete understanding of the ocean ecosystem, environmental and technical challenges as a result of observation techniques. Lack of information on the resource enabled prediction of stock that were filled with uncertainty which made it even trying to come up with a course of action.
Socioeconomic Free-For-All
Social and economic factors also influenced the decisions regarding the future of fisheries. In the Atlantic Canada, especially in Newfoundland, the cod fishery was a social and cultural identity. It was a source of livelihood for many families as they were directly and indirectly connected with the fishery as the fishers, fish sellers, fish transporters, fish plant workers, or as employees in businesses related to fishing. Companies, as well as individuals, had made big investments in the boats, infrastructure, and equipment of the fishery. This made them believe that it was best if they maintained an open access policy to the ocean and its resources. But an individual's best interest is not always the best for society in general. In the case of the northern and Newfoundland cod fishery, the maximizing of fishing was thought to be for those participating in the fishery, but instead, the ecosystem was brought to its knees, and it collapsed, leaving everyone at a loss. The 1992 moratorium was supposed to last for two years in the hope that the northern cod population would recover together with the fishery. But the damage that had already been done to the ecosystem could not be reversed. Because of the collapse of the cod fisheries, 35,000 fishers and fish plant workers were left jobless. Many communities were left devastated, and the impact was profound.
Conclusion
Within the past fifty years, there has been a drastic decline in the harvested fish population which has resulted in the collapse of many fisheries. These failures have significant adverse effects on the human economy, which will, in turn, limit income revenue and food sources for many people, as well as critical ecological and evolutionary effects. The evolutionary effects of size-selective harvesting have not been addressed; it is rather important that national and international organizations ensure they resolve these effects by continuously collecting biological data. There should be precautionary measures that are put in place so as to prevent such events from occurring. Moratoriums can be positioned to reverse effects such as evolutionary shifts in life history traits that have already taken place, but it should be introduced fast enough so as to allow natural selection for individuals with late maturation. There should be an introduction of Marine Protection Areas (MPAs) so as to be able to control the evolutionary effects of size-selective harvesting by lessening the selection pressure for smaller-sized individuals and earlier maturation, which will, in turn, preserve genetic variability. If the genes for larger-sized people are maintained, it will surely prevent the collapse of future populations. The world as a whole must put more effort so as to sustainably manage fishing if the increasing global demand is to be adequately addressed. If this situation is unable to improve fish will be too expensive for some people to afford, as well many people will lack a source of livelihood.
Work Cited
Heithaus, M.R., and B. Worm. (2013). Predicting consequences of ecological marine top predator declines. Trends in Ecology and Evolution, vol. 23 no. 4, 202-210 pp.
Helfman, G.S. (2014). Fish Conservation: a guide to restoring and understanding global aquatic biodiversity and fishery resources. Island Press, Washington, D.C., 308-312 pp.
Conover, D. O., and S.B. Munch. (2015). Sustaining Fisheries Yields Over Evolutionary Time Scales. Science, 297, 94-96 pp.
Myers, R.A., B. Worm. (2012). Rapid worldwide depletion of predatory fish communities. Nature, vol. 423, 280-283 pp.
Kuparinen, A., and J. Merila. (2017). TRENDS in Ecology and Evolution, vol. 22 No. 12, 652-659 pp.
Hilborn, R., and E. Litzinger. (2012). Causes of Decline and Potential for Recovery of Atlantic Cod Populations. The Open Fish Science Journal, vol. 2, 32-38 pp.
Hutchings, J.A., and D.J. Fraser. (2014). The nature of fisheries and farming-induced evolution. Molecular Ecology, 17: 294-313 pp.
Bard, F.X. (2016). Evolution of fishing effort of canoes targeting large pelagic fish in the Gulf of Guinea. Center for Oceanographic Research, vol. Sci. Pap. ICCAT, 52 (2), 483-487 pp.
Kuparinen. (2014). The mean trophic level of fish harvests had declined. Oxford Publishers 640-720.
OECD, F. a. (2015). The Development Dimension Fishing for Development. OECD Publishing p-7-15
