Finding Oregon's Old Female Rockfish, Science Bulletin 2023-04

Identification Information

Citation

Originator: Rasmuson, L. K, M.R. Terwilliger, E.J. Bailey, M.T.O. Blume, and K.A. Lawrence

Publish Date: April 2023

Online Link: None

BPA Project #:

Contact Information

Agency: Oregon Department of Fish and Wildlife

Name: Leif Rasmuson

Job Position: Marine Fisheries Research Project Leader

Telephone: 541-270-5561

E-Mail Address: leif.k.rasmuson@odfw.oregon.gov

Description

Abstract: Recent stock assessments for Black Rockfish (Sebastes melanops), Canary Rockfish (Sebastes pinniger) and Yellowtail Rockfish (Sebastes flavidus) have shown that there is a lack of old female rockfish in these populations from California to Alaska. This absence is based on the lack of old females in both fisheries-dependent and fisheries-independent collections, a surprising fact considering these three species live across an extreme depth range and are therefore captured by a diversity of fisheries (hook and line, long line, midwater trawl and bottom trawl). To explore potential explanations for why older females are absent from fisheries-dependent data, we examined commercial and recreational catch data as well as surveyed the commercial and recreational fleets for their expert knowledge. Neither effort resulted in a consistent pattern or association with the lack of old females in any of the three populations. Based on our analysis of fisheries-dependent data and fleet survey responses, we present multiple hypotheses for the absence of old females, each with associated arguments for, and against; as well as a short description of how each hypothesis could be tested in the future. We consider these hypotheses using the principle of parsimony, where the reason for the absence of old females in each species is assumed to be the same. Ultimately, we hypothesize that elevated natural mortality (mortality unrelated to fishing) of females relative to males is the most likely cause of their absence. The most notable fact in support of this hypothesis being that these three species occupy a wide geographic range, a diversity of habitat types, are captured in multiple fisheries, and yet, old females are consistently absent in all three species throughout their geographic ranges. Moreover, we pose that the question of “why aren’t there old females” be reframed to ask “why are there old males” for these three species? Finally, we suggest the importance of the Big Old Fat Fecund Female (BOFFF) hypothesis be reframed to impart emphasis on the Bigger Older Fatter Fecunder Females. We feel that the original phrasing gives way to only considering the oldest fish important, while the reality is reproductive output increases linearly with age, such that a middle-aged fish is increasingly more important than a younger-aged fish. The implication being that BOFFF-related reproductive benefits increase with age and are not limited to only the oldest individuals.

Purpose:

Time Period of Content: 1980-Current

Geographic Extent: West Coast USA

Status: Final

Use Constraints:

Format: PDF

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