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.
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
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.
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/