Guest Blogger: Andreas Rice
The following guest post was voted best in the class for an undergraduate assignment on fish adaptation from Cal Poly Humboldt’s Fall 2022 Fish Conservation and Management course taught by Dr. Darren Ward. The assignment required students to find a peer-reviewed article on a fascinating fish adaptation or species and to communicate the scientific information in a blog format to a general audience.
When you think of animals with extreme lifespans, elephants, clams, and tortoises might come to mind. However, extreme longevity can also be seen in West Coast rockfishes (Sebastes spp.), a genus important for food fisheries.The most extreme example from this genus is the long-lived Rougheye Rockfish (S. aleutianus) which boasts an incredible lifespan of over 200 years (Kolora et al. 2021)!That means a Rougheye Rockfish alive today could have been swimming around when Charles Darwin set off from Plymouth, England to explore the Galapagos Islands.
Rockfish habitat is usually characterized by a rocky substrate with seaweeds and macroalgae, but the Rougheye Rockfish is generally found on soft bottomed areas of the seabed with scattered boulders on slopes (COSEWIC 2007). They are found in the northern hemisphere from Japan to the Aleutian Islands, living near the ocean bottom at depths down to 1000m, though most are found in waters from 150-900 m. The water is deep and dark – light is scarce. While Rougheye Rockfish can live in water temperatures as low as 31oF, they prefer around 39oF (Eschmeyer et al. 1983; Froese 2020).
Some scientists hypothesize that animals that live in colder waters tend to live longer. Kolora et al. (2021) took it one step further by finding out what genes may be affecting lifespan. To understand what makes these fish so long lived, Kolora et al. (2021) mapped out the genome of the Rougheye Rockfish along with 87 other rockfish species. They found positive selection for 16 genes that are associated with DNA repair and maintenance in Rougheye and other long-lived rockfish (Kolora et al. 2021). Some of these same patterns of selection can be found in other long-lived species such as bowhead whales and giant tortoises. This suggests convergent evolution associated with longevity in these completely unrelated groups (Kolora et al. 2021).
Maximum Rougheye Rockfish fecundity (i.e., reproductive potential) depends on living an extremely long time. At the height of sexual maturity, a female Rougheyewill produce around 700,000 eggs per spawn (Kolora et al. 2021). This sounds like a lot, but when compared to other commercially and recreationally fished species such as the shorter-lived Black Rockfish (S. melanops), with an egg count of 1.5 million eggs, or Yelloweye Rockfish (S. ruberrimus)with 1.25 million eggs, it’s not. Only if Rougheye are allowed to live to their max lifespan of 200 years, can their total lifetime fecundity be comparable to the more prolific Black Rockfish and other shorter-lived species (see graph; Kolora et al. 2021).
Problems arise because the Rougheye Rockfish is vulnerable to overfishing. Because it takes up to 20 years to reach maturity, certain fishing practices can harvest individuals before they even have a chance to reproduce (Fisheries and Oceans Canada 2020).
Without proper fisheries management this species, along with many other long-lived groundfish, can quickly become locally extinct or entirely extinct. As a community of fishers and consumers, we can innovate solutions to protect our ocean’s natural heritage as well as what reaches our dinner plate. One option is to avoid harvesting Rougheye Rockfish all together, but this becomes complicated to justify when some fisherman make a living by catching and selling these fish. However, with adaptive management techniques, we can decide how many fish can be harvested or what size fish can be taken to better ensure our fisheries are more sustainable.
While some of the broader solutions are beyond us as individuals, one thing we can do is raise awareness about the rockfish release device or fish descender. If recreational harvest of Rougheye Rockfish is allowed, using a rockfish release device would allow fish that are suffering from barotrauma, a condition where deep sea fish have their stomachs protrude from their mouth due to the rapid change of pressure, to be released safely back into the water if they are not to be kept. This would ensure that these centenarians can live to breed another day.
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About the author:
Hello, my name is Andreas Rice, and I am a transfer student at Cal Poly Humboldt. I have a passion for the natural world, exploring subjects and sites from the open ocean to the tallest mountains. I especially enjoy topics in aquaculture and hope to re-invigorate our coastal fisheries by means of species management and protection.
Clausen, D. M., Fujioka, J. T., & Heifetz, J. (2003). Shortraker/rougheye and other slope rockfish. Stock assessment and fishery evaluation report for the groundfish resources of the Gulf of Alaska, 531-572.
COSEWIC 2007. COSEWIC assessment and status report on the rougheye rockfish Sebastes sp. type I and Sebastes sp. type II in Canada. Committee on the Status of Endangered Wildlife in Canada. Ottawa. viii + 36 pp.
Eschmeyer, W.N., Herald. E.S. & Hammann, H. (1983). A field guide to Pacific coast fishes of North America. Boston (MA, USA): Houghton Mifflin Company. 336 p.
Fisheries and Oceans Canada. (2020). Rougheye/blackspotted rockfish (sebastes aleutianus/melanostictus. Retrieved December 9, 2022.
Kolora, S. R., Owens, G. L., Vazquez, J. M., Stubbs, A., Chatla, K., Jainese, C., Seeto, K., McCrea, M., Sandel, M. W., Vianna, J. A., Maslenikov, K., Bachtrog, D., Orr, J. W., Love, M., & Sudmant, P. H. (2021). Origins and evolution of extreme life span in Pacific Ocean rockfishes. Science, 374(6569), 842–847.
Froese, R., (2020). R code (PrefTempBatch_5.R) to estimate preferred temperature from AquaMaps (ver. 10/2019). As cited in Froese, R. and D. Pauly. Editors. (2022). FishBase.