“Cod population changed in response to intensified fishing”

“New research by scientists at the University of Iceland’s Research Centre of the Westfjords and their colleagues has revealed that the trophic niche of the Atlantic cod in Icelandic coastal regions remained stable for centuries, but changed in the 19th century alongside intensified fishing. It is likely that this reflects changes to both the age and size of the cod stocks, but also changes to marine food webs as populations fall due to extensive fishing and food chains shorten. The research was reported in Scientific Reports, a respected journal from the publishers of Nature. According to the authors of the study, the results underline the importance of conserving different migratory cod in Icelandic coastal regions, for example to boost the population’s resilience to environmental changes.

The research team included Guðbjörg Ásta Ólafsdóttir, biologist and director of the UI Research Centre of the Westfjords, and Ragnar Edvardsson, archaeologist at the Research Centre, along with their colleagues in Canada and Norway. 

Guðbjörg Ásta and Ragnar have worked together for many years on interdisciplinary research into fish bones, particularly cod, that they have excavated from ancient fishing stations in the Westfjords. The oldest bones are 1000 years old.  “The main aim of the research is to understand how changes in fishing and the marine environment have affected fish populations over the centuries. Using a data series spanning several centuries, we can establish a kind of baseline and try to estimate how extensive human exploitation could have affected marine ecosystems,” explains Guðbjörg Ásta. “

Read the full article here and the scientific article here.

Planet Alaska: Woven with herring

“Down on the dock I say, “Gunalchéesh,” as my friend hands me a five-gallon bucket filled with herring eggs on hemlock branches. I take the bucket home and start a small pot of water boiling. I blanch a small batch of eggs and then eat them with soy sauce. It tastes like home. I am home when I eat herring eggs. Later, I take the herring eggs around to friends and elders. Sharing is an important Tlingit value and sharing herring eggs is a ritual connecting me to my people and place. This ritual is in danger of being lost.

Sadly, we are running out of time to save the herring. The herring fishery in Southeast Alaska is one of our “canaries in the cave,” meaning the herring decline is an early indicator of problems throughout our food web. One after another, 11 herring management areas in Southeast Alaska have been over-fished to near extinction. Extinction is a serious word. Historical herring fisheries once thrived at Kah Shakes/Cat Island, West Behm Canal, Ernest Sound, Hobart Bay, Seymour Canal, Chatham Strait, Hoonah Sound, Tenakee Inlet, Auke Bay, Lynn Canal, Icy Strait and Yakutat Bay. The Sitka Sac Roe Fishery is the last population of herring in Alaska to provide a significant commercial harvest and subsistence herring egg harvest. Despite these losses, Alaska Department of Fish and Game has ignored the traditional ecological science and testimonials of the Tlingit who’ve harvested in a sustainable way here for more than 10,000 years. Mismanagement has resulted in the decline of our herring population. This frightens me. Our elders tell us that life in Southeast is not possible without the herring. Why is this so hard for the state of Alaska to understand?”

Read the full Juneau Empire article here

15873891_web1_herring-eggs-sitka-branches-115873891_web1_53470224_680297099054460_2200044199343030272_nTop: Herring eggs hang from a hemlock branch in Sitka. (Courtesy Photo | Vivian Prescott), Bottom: In this photo from the William L. Paul Sr. Archives, herring eggs dry on the beach in Sitka circa 1900 (Courtesy Photo | Sealaska Heritage Institute).

Overfishing, CPUE, and Commercially Extinct Species. 

Overfishing, CPUE, and Commercially Extinct Species. 
February, 17, 2019. By Megan Lorino

University of Port Elizabeth published an article in 1981 on the topic of catch per unit effort using gill-nets in the Sundays River estuary of South Africa. Their data was obtained from 55 catches using gill-nets. Nets were positioned in lower, middle, and upper reaches of the estuary. Each site was selected with avoidance of boat traffic in mind. Measurements were taken of salinity as well as (surface) water temperature of each site. CPUE was recorder for each caught species on a monthly basis and always included number per species as well as weight of each given species.

The most abundantly caught species was the sea catfish Tachysurus feliceps which totaled 226 individual fish, followed by the flathead mullet Mugil cephalus with a total of 191 individual fish, the souther mullet Liza richardsoni with a total of 185 individual fish, and the kob Argyrosomus hololepidotus with a total of 175 individual fish. The Argyrosomus hololepidotus (kob) was the  dominant catch in terms of weight, weighing 315kg, followed by the spotted grunter Pomadasys commersonni weighing 165kg. This particular study was to evaluate the abundance of varying species within the communities of the Eastern Cape estuaries. Gill-nets were set up between 1976 and 1979. 1,258 total fish were caught during this study. The CPUE (catch per unit effort) was 21kg/standard net.

 

References
Marais, J. (1981) African Journals Online. African Zoology. Seasonal abundance, distribution, and catch per unit effort using gill-nets, of fishes in the Sundays estuary. Retrieved from https://www.ajol.info/index.php/az/article/view/152270/141866

 

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Commercial extinction (of fish) is determined when a particular species of fish has become too rare to be caught for profit any longer. This occurs after a process of depletion – the reduction of that particular species due to overfishing. Recovery from overfishing causing an oceanic fishery to collapse can be combatted in several ways. One way is to create stronger regulations and plans of action toward illegal fishing in order to give stocks a chance to recover. More aggressive fisheries management, the increased use of aquaculture, and better law enforcement of catch-governing laws could all help to reduce overfishing and restore populations. Illegal fishing and unsustainable harvesting of fish is still one of the biggest issues causing overfishing that needs to be managed more diligently in order to really save our fish populations and truly reduce overfishing.

 

References
Doyle, A. (2015) Reuters. Ocean fish numbers on ‘brink of collapse’: WWF. Retrieved from https://www.reuters.com/article/us-environment-oceans/ocean-fish-numbers-on-brink-of-collapse-wwf-idUSKCN0RG1JW20150916

National Geographic (2010) Overfishing. Retrieved from https://www.nationalgeographic.com/environment/oceans/critical-issues-overfishing/