In the News: The Oldest and Fattest Females Produce the Best Offspring

Recent studies have suggested that the oldest females offer the best chance of survival for their progeny, with eggs of the oldest (and presumably biggest) female black rockfish having the best probability of survival under a variety of conditions, according to a presentation at the 5th Annual Member Meeting of the Marine Fish Conservation Network. It seems that fishing the largest fish from the population would have a greater impact on the population than previously thought. We assume that eggs from young animals is just as viable and likely to survive as eggs from an older adult, when in fact research suggests that fish born from the eggs of the oldest female have an extra edge over other young. The implications for Fisheries Management could have staggering effects, and the authors of the studies advise measures above and beyond just fishing limits.

The Magnuson –Stevens Act (MSA), enacted in 1976 and amended in 1996 with the Sustainable Fisheries Act, establishes a national framework for conserving and managing marine fisheries. It’s power to stop overfishing was tested this past year. The National Oceanic and Atmospheric Administration received an unprecedented number of negative comments from the public regarding proposed changes to the National Standard One, the part of the MSA that governs the principles of management of the nation's fisheries. With the overwhelming majority of the comments supporting the strengthening of the National Standard One, NOAA reinstated the MSA with language emphasizing the vital role of ecosystem-based approaches to fisheries management.

The authors of Maintaining Old Growth Age Structure: Implications for Fisheries Management postulate that even fishing at ‘sustainable’ levels ensures there are not as many big fish left in a population. Bigger female fish produce more viable eggs and at much greater quantities. Since a 40 cm bocaccio rockfish makes 200,000 eggs per year, where a 80-cm fish produces over 2 million eggs, Berkeley et al state: "In other words, considering only fecundity per se – let alone egg or larval quality – a single 80-cm bocaccio is worth nearly ten 40-cm fish.” Old female rockfish’s larvae have a better chance at life as they are born during peak food availability, grow faster, and survive at higher rates. Yet the biggest, fattest, oldest females are the first to be fished out. The authors maintain that marine protected areas are the most feasible route to protect fish whose populations depend on old fish to flourish, in addition to regular fisheries management. They postulate that stopping overfishing of fish populations is only the first step to ensuring there are old big fat female fish left for generations.

 

Read more about overfishing:

Conserve Our Ocean Legacy (COOL) launched a campaign opposing NOAA Fisheries' proposal to cut National Standard 1.

Fisheries Science: How many more fish in the Sea? from Nature International Weekly Journal of Science questions the single-species approach to fisheries management.

 

Articles cited:

Berkeley, S. A., M. A.  Hixon, R. J. Larson, and M. S. Love. 2005. Maintaining Old Growth Age Structure: Implications for Fisheries Management. Marine Fish Conservation Network, 5th Annual Member Meeting, June 7, 2005. Abstract presentation.

Berkeley, Steven A., Chapman, Colin, Sogard, Susan M. 2004: Maternal Age as a determinant of Larval Growth and Survival in a Marine Fish, Sebastes melanops . Ecology: 85: 1258–1264.