Where Are the Fish Going? Unsustainable Fishing Practices Leading to Fishery-Induced Evolution

By Amanda Deverson

“Our oceans are being plundered”(WWF, n.d, 1.). Many people rely on seafood to survive, whether it is their main source of protein or their livelihood. Overfishing and overexploitation of many fish species is leading to the full collapse, or soon to collapse entirely, in the commercial fisheries. Overfishing has resulted in full exploitation of 53% of the world’s fisheries and an additional 32% of fisheries have been considered overexploited, depleted, or are actively trying to recover from depletion. Many important commercial fishing populations have declined to levels that threaten the overall survival of the population (WWF, n.d. 1). Important species of fish caught commercially for food include cod and salmon (Enberg, et al., 2009 & Hard, et al., 2008). If commercial fishing continues as it is now, most commercial fish species will potentially never recover by 2048 due to the lack of diversity in our oceans (Kurlansky, 2014).

Unsustainable fishing methods catch and harvest fish at a rate that is not sustainable. Fishing methods that are seen as unsustainable include gill nets, bycatch, trawling, overfishing, etc. (WWF, n.d. 1)

Fish species that evolve at an earlier age of maturity, tend to have slower life histories. When there are not as many large fish to be caught, smaller ones are harvested which does not allow enough time for them to reach sexual maturity. Not only does this action affect the population’s life history traits, but it is also an unsustainable process. Rapid fishery-induced evolution has started to be seen as a result of such aggressive and high-intensity commercial fishing practices. If these changes are considered with fishery-induced evolution in mind, management can make better decisions based on benefits, profits, and yields (Fiag, 2015).

Overfishing Practices

Coastal and pelagic (open ocean) commercial fisheries have begun to collapse globally (WWF, n.d. 1). As these areas have become depleted, fisheries have begun to target deep ocean areas and species that have not been previously exploited. Some of the newly targeted fish species include monkfish, Patagonian toothfish, blue ling, and orange roughy. Due to this shift in focus, these species have already begun to see signs of overexploitation. Currently, around 40% of the world’s fishing grounds are now in  ocean waters that are deeper than 200 m (WWF, n.d. 1).

Why is this happening?

• Illegal fishing companies don’t respect fishing laws and agreements
• Subsidies that keep too many boats on the water
• Unregulated fishing agreements that allow foreign fleets to overfish in waters of developing countries
• Destructive and unsustainable fishing practices being utilized (gill nets, bycatch, trawling)
• Poor fisheries management
• Bycatch events involving juvenile fish and other marine species (WWF, n.d. 1)

Examples of Overfished Commercial Fisheries that have collapsed

Many commercial fisheries have collapsed due to overfishing and some have begun to recover. Recovery of commercial fisheries is a very slow and unpredictable process (Pedersen, et al., 2017). Here are some examples of fishery collapse and some recoveries.

Atlantic Northwest Cod

The Atlantic cod (the northern cod stock) is the population in the north-west Atlantic Ocean. It has been an important fishery for hundreds of years but has seen a significant decline since the 1980s. The fishery fully collapsed and fishing was closed in July 1992. The original closure of the fishery was supposed to be for two years, but that did not give the cod enough time to recover (Pedersen, et al., 2017). Before the full closure of the fishery, the size and age of mature fish had decreased. Even though there has been significantly less fishing of this fishery in the past decade, the size and age of mature fish has still not recovered (Kuparinen and Merilä, 2007).

Salmon

Anadromous salmon are those that live in both marine and freshwaters and then return to the rivers they were born in to reproduce. Due to their high nutritional value and ease of being caught, they have been heavily exploited by humans. The chinook salmon stock from the Sacramento – San Joaquin River system in the Central Valley of California collapsed in 2007/2008. They have been overharvested by humans, but they have faced many other issues including habitat loss, blocked spawning areas, and diversions due to the construction of dams. Since the collapse of the fishery, studies have shown that efforts to recover the population from the use of hatcheries has led to more hatchery fish than wild fish in the river system. This poses other threats that we have yet to see the full effect of (Willmes, et al., 2017).

Orange roughy

Orange roughy are deep water fish (500 – 1,500 m deep) that grow slowly, live very long lives, and have lower levels of fertility and productivity. These factors make the orange roughy more vulnerable to overfishing and are highly valuable (Clark, 2001).  The commercial fishery for orange roughy did not open until around 1979 in the Atlantic and then later in the waters of New Zealand. In New Zealand, orange roughy were still the fourth most valuable fish species in 2005 (Francis and Clark, 2005).

White Abalone

White abalone were commonly found at the depths of 50-180 feet back in the early 1970s at the Channel Islands off the coast of California. In the 1970s, it was calculated that there would have been between 6,120 and 30,600 individuals within that same area (Davis, Haaker, and Richards, 1996). For quite some time, scientists have thought that marine invertebrates were extremely resistant to overfishing. White abalone have significantly declined and even disappeared completely from their known normal range. Deeper water locations have also been surveyed and it was found that populations continue to decline currently and show no signs of recruitment of the animal. This is even after the fisheries of the white abalone were officially closed in 1997 (Rogers-Bennett et al., 2016). For the white abalone to successfully spawn, they must be in high density areas and close together; otherwise, reproduction is nearly impossible.

Various marine laboratories across the State of California are working to recover the white abalone species through breeding programs and studies on the ecological needs of the species. The captive breeding program started with 54 individual abalone dispersed across the laboratories (Scully, 2014). In 2012, marine laboratories like Bodega Marine Laboratory – University of California, Davis were able to start a successful spawning program and continue to increase their success every year (Deverson, 2019).

Current “most threatened” species of overfishing (Mok, 2020):

Threatened species due to bycatch:

Unsustainable Fishery Affects Cause of the Evolution

Overfishing can lead to a domino effect of issues, especially when it comes to keystone species, the most depended on species of an ecosystem, being affected. Once the larger and older fish have disappeared, the mammals that rely on them for food will then start to die off due to lack of food. For example, dolphins will need to seek out other sources of food when the bluefin tuna begin to disappear. Smaller fish that are chased to the surface of the ocean by larger predator fish would consequently stay away from the surface waters. This would then cause a food shortage for seabirds. Without seabirds to discard food onto the beaches, crabs, insects, and lizards would suffer as well (Kurlansky, 2014).

Continuous Evolution

Changes in the biological aspects of fish populations need to be updated and monitored constantly (Enberg, et al., 2009). Aquaculture, farming fish/fish hatcheries, and proper management are all steps in the right direction to take the pressure off of the wild populations of fisheries in peril.

Two of the main factors that affect the evolution rate in a fishery that has already been overexploited are size selectivity of the fishery and the intensity of which the fish are harvested. Each case of overexploitation is different and the plan of action must be assessed on a case to case basis. Marine Protected Areas (MPAs) have been a strongly suggested way of controlling evolutionary impacts of overfishing (Kuparinen and Merilä, 2007). Also keeping in mind the regulations put in place like the MPAs are limited to the countries that implement them. There are other countries who have over exploited fish populations as well with little, laxed, or no regulations in place.

What can we do? (MBA, n.d.): 

A great example of a program designed to help consumers make an informed decision about the seafood they are purchasing is the Monterey Bay Aquarium’s (MBA) Seafood Watch program. You can search for your area on https://www.seafoodwatch.org/ Their site offers a search bar to search for any specific seafood you enjoy and see what the status of it is and if it is the best choice for you and the ocean. This program is accessible for many audiences in both an app form and a simplified card that you can print at home.

The Seafood Watch Program at the Monterey Bay Aquarium website offers many articles on the following ways we can help with the sustainability of seafood:

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My name is Amanda Deverson and I’m currently in my final year of graduate school. I will be receiving my M.A. in Biology at Miami University through Project Dragonfly and San Diego Zoo Wildlife Alliance. I was born and raised in the desert but have always felt my happiest at the beach. I have always had a passion for marine conservation and have spent a great deal of time volunteering, interning, and working with like minded organizations. I hope to continue work in the preservation of marine biodiversity and marine conservation after I finish my degree at the end of this year.

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References

• Clark, M. (2001). Are deepwater fisheries sustainable?—the example of orange roughy (Hoplostethus atlanticus) in New Zealand. Fisheries Research, 51(2-3), 123-135.
• Davis, G.E., Haaker, P.L., and Richards, D.V.. (1996). Status and trends of White Abalone at the California Channel Islands. Transactions of the American Fisheries Society. 125(1) 42-48
• Deverson, A. (2019) White Abalone: The Decline and Ongoing Recovery of an Endangered Marine Invertebrate. Unpublished manuscript https://docs.google.com/document/d/1LMedNzLN6MOjy8-DJMbCMG3MDZ13veJx5FqlwgE9dxg/edit?usp=sharing
• Enberg, K., Jørgensen, C., Dunlop, E. S., Heino, M., & Dieckmann, U. (2009). Implications of fisheries‐induced evolution for stock rebuilding and recovery. Evolutionary Applications, 2(3), 394-414.
• Faig, A. (2015). The economic gains to accounting for fishery induced evolution. Unpublished manuscript.
• Francis, C. R., & Clark, M. R. (2005). Sustainability issues for orange roughy fisheries. Bulletin of Marine Science, 76(2), 337-352.
• Hard, J. J., Gross, M. R., Heino, M., Hilborn, R., Kope, R. G., Law, R., & Reynolds, J. D. (2008). Evolutionary consequences of fishing and their implications for salmon. Evolutionary Applications, 1(2), 388-408.
• Kuparinen, A., & Merilä, J. (2007). Detecting and managing fisheries-induced evolution. Trends in ecology & evolution, 22(12), 652-659.
• Kurlansky, M. (2014). Introduction. In World without fish (pp. Ix-20). New York: Workman Publishing.
• MBA (n.d.). Monterey Bay Aquarium Seafood Watch Program. Seafood watch – official site of the monterey bay aquarium’s sustainable seafood program.  https://www.seafoodwatch.org/.
• Mok, K. (2020, May 7). So much for Fish & Chips: Greenpeace list of Most OVER-FISHED SPECIES. Treehugger. https://www.treehugger.com/so-much-for-fish-chips-greenpeace-list-of-most-over-fished-species-4858646.
• Pedersen, E. J., Thompson, P. L., Ball, R. A., Fortin, M. J., Gouhier, T. C., Link, H., … & Pepin, P. (2017). Signatures of the collapse and incipient recovery of an overexploited marine ecosystem. Royal Society open science, 4(7), 170215.
• Rogers-Bennett, L., Aquilino, K.M., Catton, C.A., Kawana, S.K., Walker, B.J., Ashlock, L.W., Marshman, B.C., Moore, Taniguchi, Gilardi, and Cherr. (2016). Implementing a restoration program for the endangered White Abalone (Haliotis sorenseni) in California. Journal of Shellfish Research. 35(3) 611-618.
• Scully, S. (2014). Bodega Bay researchers help endangered abalone breed. Retrieved from https://www.pressdemocrat.com/news/2212739-181/bodega-bay-researchers-help-endangered?sba=AAS
• Willmes, M., Hobbs, J. A., Sturrock, A. M., Bess, Z., Lewis, L. S., Glessner, J. J., … & Kindopp, J. (2018). Fishery collapse, recovery, and the cryptic decline of wild salmon on a major California river. Canadian Journal of Fisheries and Aquatic Sciences, 75(11), 1836-1848.
• WWF (n.d.) Poor fisheries management. Retrieved October 1, 2020, from https://wwf.panda.org/our_work/our_focus/oceans_practice/problems/unsustainable_fishing/

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This piece was prepared online by Panuruji Kenta, Publisher, SEVENSEAS Media