"Northern Rock Sole"

Northern rock sole (Lepidopsetta polyxystra) are assessed on a biennial stock assessment schedule as part of the National Marine Fisheries Service assessment prioritization plan implemented in 2017.

The Gulf of Alaska (GOA) northern and southern rock sole assessment has been moved to a 4-year assessment cycle per the stock assessment prioritization schedule. During years when a full assessment is not completed a partial assessment will be done. This year marks a partial assessment year. The last full assessment was completed in 2017 and marked the first year of the new assessment schedule.

The 2018 bottom trawl survey point estimate is a 21% decrease from the 2017 estimate. These two estimates are the lowest in the past 25 years and have the effect of lowering the assessment model time series abundance estimates relative to the last full assessment conducted in 2016. The model results indicate that the stock condition has been at a high and stable level but in a slow decline for the past 9 years. The female spawning biomass is now at a peak and is starting to decline as a result of the combination of strong recruitment from the 2001-2003 and 2005 year classes, which are presently at the age of maximum cohort biomass, and light fishery exploitation. Model 15.1 is the preferred model evaluated in this assessment. Models 18.1 through 18.3 represent Model runs made to examine alternate states of nature for contrast to the primary models results. Ensemble modeling was also investigated.

Rock sole research in the Bering Sea and Gulf of Alaska.

The Alaska Fisheries Science Center Age and Growth Program published a practical guide to the age determination of key groundfish species from Alaskan waters.

The National Standard Guidelines for Fishery Management Plans published by the National Marine Fisheries Service (NMFS) require that a stock assessment and fishery evaluation (SAFE) report be prepared and reviewed annually for each fishery management plan (FMP). The SAFE reports are intended to summarize the best available scientific information concerning the past, present, and possible future condition of the stocks and fisheries under federal management. The FMPs for the groundfish fisheries managed by the Council require that drafts of the SAFE reports be produced each year in time for the December North Pacific Fishery Management Council (Council) meetings.

The Stock Assessment and Fishery Evaluation (SAFE) report summarizes the best available scientific information concerning the past, present, and possible future condition of the stocks, marine ecosystems, and fisheries that are managed under Federal regulation. It provides information to the Councils for determining annual harvest levels from each stock, documenting significant trends or changes in the resource, marine ecosystems, and fishery over time, and assessing the relative success of existing state and Federal fishery management programs. For the FMP for the Groundfish Fishery of the Bering Sea and Aleutian Islands (BSAI) Area, the SAFE report is published in three sections: a “Stock Assessment” section, which comprises the bulk of this document, and “Economic Status of Groundfish Fisheries off Alaska” (i.e., the “Economic SAFE report”) and “Ecosystem Considerations” sections, which are bound separately.

Assessment for northern and southern rock sole which are part of the shallow water flatfish complex has been moved to a biennial schedule to coincide with the expected receipt of new survey data.  Usually, on alternate (even) years we will present an executive summary with last year’s key assessment parameters and projections for this year. 

Northern rock sole (Lepidopsetta polyxystra n. sp.) are distributed primarily on the eastern Bering Sea continental shelf and in much lesser amounts in the Aleutian Islands region. Two species of rock sole are known to occur in the North Pacific Ocean, a northern rock sole (L. polyxystra) and a southern rock sole (L. bilineata) (Orr and Matarese 2000). These species have an overlapping distribution in the Gulf of Alaska, but the northern species comprise the majority of the Bering Sea and Aleutian Islands populations where they are managed as a single stock.

Rock sole are demersal fish that can be found in shelf waters to 600 m depth (Allen and Smith, 1988). Two species of rock sole are known to occur in the north Pacific Ocean, northern rock sole (Lepidopsetta polyxystra) and southern rock sole (L. bilineata) (Orr and Matarese, 2000). Adult northern rock sole are found from Puget Sound through the Bering Sea and Aleutian Islands to the Kuril Islands, while the southern rock sole range from the southeast Bering Sea to Baja California (Stark and Somerton, 2002). These species have an overlapping distribution in the Gulf of Alaska (Wilderbuer and Nichol, 2009). Rock sole are most abundant in the Kodiak and Shumagin areas. The northern rock sole spawns in midwinter and spring, and the southern rock sole spawns in summer (Stark and Somerton, 2002). Northern rock sole spawning occurred in areas where bottom temperatures averaged 3°C in January, and southern rock sole spawned in areas where bottom temperatures averaged 6°C in June (Stark and Somerton, 2002). Rock soles grow to approximately 60 cm and can live in excess of 20 years.