Profile updated on 28 February 2018





Sebastes diploproa


Splitnose rockfish


rock cod

Splitnose rockfish (Sebastes diploproa) are distributed from the northern Gulf of Alaska (Prince William Sound) to central Baja California and occur at depths between 91-795 meters. Adults are the most abundant between British Columbia and southern California at depths from 215 to 350 meters (Alverson et al. 1964, Gunderson and Sample 1980, Love et al. 2002).

Splitnose rockfish co-occur with an assemblage of slope rockfish, including Pacific ocean perch (Sebastes alutus), darkblotched rockfish (Sebastes crameri), yellowmouth rockfish (Sebastes reedi), and sharpchin rockfish (Sebastes zacentrus) off Washington and Oregon, and striptail rockfish (Sebastes saxicola), darkblotched rockfish and shortspine thornyhead (Sebastolobus alascanus) off central California. 

This species is explored commercially off the continental coast of the United States from the U.S.-Canadian border in the north to the U.S.-Mexican border in the south. Splitnose rockfish have been caught primarily in fisheries for mixed slope rockfish or other deepwater targets.

Belonging to a multispecies complex fishery, this rockfish is not consistently sorted to species, and landings are estimated from applying port sampling species compositions to mixed rockfish landings. Trawl landings on average comprise 90% of annual catches, with 80% of fish landed in California. Only 10% of splitnose rockfish on average are caught by non-trawl commercial fisheries. The vast majority of non-trawl landings are caught by net gear, and only a small portion is caught by hook-and-line in the sablefish fishery. This species is rarely taken in the recreational fishery (Gertseva et al. 2009).

There are no clear stock delineations for splitnose rockfish in the U.S. waters. No molecular markers have yet been developed for this species, and no genetic data are currently available to suggest the presence of several stocks (Waples et al. 2008). Within the assessment area the resource is treated as a single stock due to the lack of biological and genetic data supporting the presence of multiple stocks. Nevertheless, management decisions on a coast-wide population need to account for effort concentration, since abundance is higher in some areas such as off central California.


No related analysis


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No related FIPs


No related MSC fisheries


Within FishSource, the term "fishery" is used to indicate each unique combination of a flag country with a fishing gear, operating within a particular management unit, upon a resource. That resource may have a known biological stock structure and/or may be assessed at another level for practical or jurisdictional reasons. A fishery is the finest scale of resolution captured in FishSource profiles, as it is generally the scale at which sustainability can most fairly and practically be evaluated.

US west coast Northern US west coast United States Bottom trawls
Southern US west coast United States Bottom trawls





Last updated on 16 November 2016

The research and data needs include:

1) Genetic studies of splitnose rockfish stock structure in the Northeast Pacific ocean;

2) Comprehensive historical reconstruction of splitnose rockfish catches in Oregon and Washington;

3) Age-determination and age-validation studies to develop a consistent set of aging criteria for the species that could help reduce the differences among agers;

4) Histological studies of splitnose rockfish maturity to reliably estimate and reduce uncertainty in female maturity parameters;

5) Studies of the spatial dynamics of splitnose rockfish to better understand their distribution and explain increased availability of the species off California in 1998;

6) Further exploration of climate-growth relationships for splitnose rockfish and incorporation of this relationship into the stock assessment model.

It is also very important to continue to monitor discard in order to improve the accuracy of total catch estimates.

(Gertseva et al. 2009)

Reference Points

Last updated on 16 Nov 2016

Unfished spawning stock output for splitnose rockfish was estimated to be 12853 million eggs (95% confidence interval: 9105-16601 million eggs). The management target for splitnose rockfish is defined as 40% of the unfished spawning output (SB40%), which is estimated by the model to be 5141 million eggs (95% confidence interval: 3642-6641 million eggs) (Gertseva et al. 2009).

The stock is declared overfished if the current spawning output is estimated to be below 25% of unfished level. The MSY-proxy harvest rate for splitnose rockfish is SPR=F50%, which corresponds to an exploitation rate of 0.033. This harvest rate provides an equilibrium yield of 1236 mt at SB40% (95% confidence interval: 883-1589 mt). The model estimate of maximum sustainable yield (MSY) is 1268 mt (95% confidence interval: 906-1630 mt). The estimated spawning stock output at MSY is 4121 million eggs (95% confidence interval: 2900-5342 million eggs). The exploitation rate corresponding to the estimated SPRMSY of F44% is 0.039 (Gertseva et al. 2009).


Last updated on 16 November 2016

The assessment shows that the stock of splitnose rockfish in the U.S. West Coast is currently at 66% of its unexploited level and, therefore, not overfished. Historically, the abundance of splitnose rockfish was estimated to have dropped below the SB40% management target in 1995, after experiencing sharp reductions from the large catches by foreign fishery in mid-1960s and increasing domestic catches in 1980s (Gertseva et al. 2009).

However, the spawning stock has been increasing since the early 2000s, and stayed above the SB40% management target since 2003. The assessment identifies two historical periods in which exploitation rates exceeded the current FMSY proxy harvest rate: during the foreign fishery peak in the mid 1960s, and in 1998 (Gertseva et al. 2009).


Last updated on 16 Nov 2016

The landed catch of splitnose rockfish was reconstructed back to 1900 from variety of published sources and databases. The fishery removals were divided among three fisheries - domestic trawl, foreign trawl and domestic non-trawl. Landings peaked in the 1960s, when foreign trawl fleets operated in U.S. waters, and reached 5313 mt in 1967. The highest catch by domestic fleets was in 1998, when 1526 mt of splitnose rockfish was landed. For the last ten years landings were relatively low and ranged between 65 and 274 mt (Gertseva et al. 2009).

After 1998 splitnose landings dropped significantly, at least in part due to management measures aimed to rebuilding darkblotched rockfish and Pacific ocean perch. Landings have ranged between 62 and 273 metric tons during the last 10 years (Gertseva et al. 2009).



Last updated on 16 November 2016

In the northern area, splitnose has been managed under trip limits for minor slope rockfish since 1999. For 2000, harvest specifications for splitnose rockfish were set for the Conception and Monterey INPFC areas only, and 48 metric tons for the Eureka area were added to the northern minor rockfish ABC (Gertseva et al. 2009).

Last updated on 16 November 2016

In 1999, after unusually high splitnose rockfish catches in 1998 that were mostly landed in California, splitnose rockfish for the first time were individually separated from the Sebastes complex in the southern area. Individual Allowable Biological Catch (ABC) and Optimum Yield (OY) for splitnose rockfish in that area have been specified along with splitnose-specific trip limits (Gertseva et al. 2009).


Other Species

Last updated on 16 November 2016

The Westcoast Groundfish Observer program reported that the discard rates for the last several years ranged between 46% and 80% coast-wide (Gertseva et al. 2009).

FishSource Scores




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No related analysis

Fishery Improvement Projects (FIPs)

No related FIPs


Marine Stewardship Council (MSC)

No related MSC certifications


  1. Love, M.S., Yoklavich, M., Thorsteinson, L. 2002. The Rockfishes of the Northeast Pacific. University of California Press, Berkeley

  2. Gunderson, D.R., Sample, T.M. 1980. Distribution and abundance of rockfish off Washington, Oregon, and California during 1977. Marine Fisheries Review 42: 2-16

  3. Alverson, D.L., Pruter, A.T., Ronholt, L.L. 1964. A study of the Demersal Fishes and Fisheries of the Northeastern Pacific Ocean. H.R. MacMillan Lectures in Fisheries. Institute of Fisheries, University of British Columbia, Vancouver

  4. Waples, R.S., Punt, A.E., Cope, J.M. 2008. Integrating genetic data into management of marine resources: how can we do it better? Fish and Fisheries 9: 423-449

  5. Gertseva V.V., Cope J.M., Pearson D.E. 2009. Status of the U.S. splitnose rockfish (Sebastes diploproa) resource in 2009. SAFE Final Report, 28th OCtober 2009. 272pp.

  6. Medley, P.A.H., O’Boyle, R., Pedersen, M.G., Tingley, G.A., Hanna, S. S., Devitt, S., 2014. MSC Assessment Report for United States West Coast Limited Entry Groundfish Trawl Fishery. Version 6: Public Certification Report. Intertek Fisheries Certification, June 2014. 403pp



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    Splitnose rockfish - US west coast

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