"Sablefish"

Previous studies have shown rapid mixing of sablefish (Anoplopoma fimbria) among fishery regulatory areas, with the pattern of movement related to fish size. > 300,000 tag releases in Alaska and over 27,000 tag recoveries from 1979 to 2009 were analyzed.

Changes in the input data: New data included in the assessment model were relative abundance and length data from the 2015 longline survey, relative abundance and length data from the 2014 longline fishery, length data from the 2014 trawl fisheries, age data from the 2014 longline survey and 2014 fixed gear fishery, the 2015 Gulf of Alaska trawl survey abundance and length compositions, updated catch for 2014, and projected 2015- 2017 catches.

Sablefish (Anoplopoma fimbria) inhabit the northeastern Pacific Ocean from northern Mexico to the Gulf of Alaska (GOA), westward to the Aleutian Islands (AI), and into the Bering Sea (BS) (Wolotira et al. 1993). Adult sablefish occur along the continental slope, shelf gullies, and in deep fjords, generally at depths greater than 200 m. Sablefish observed from a manned submersible were found on or within 1 m of the bottom (Krieger 1997). In contrast to the adult distribution, juvenile sablefish spend their first two to three years on the continental shelf of the GOA, and occasionally on the shelf of the southeast BS. The BS shelf is utilized significantly in some years and seldom used during other years (Shotwell et al. 2012).

Stock assessment and fishery evaluation reports archive from 1998–2012.

Over 34,000 age 0–2 juvenile sablefish (Anoplopoma fimbria) were tagged and released in southeast Alaska waters during 1985–2005. The data set resulting from this tagging study was unusual because of its time span (20 years) and because age could be reliably inferred from release length (i.e., tagged and released fish were of known age); thus, age-specific movement patterns could be examined. The depth-and area-related recovery patterns supported the concepts that sablefish move to deeper water with age and migrate counterclockwise in the Gulf of Alaska. Availability to the fishery increased rapidly for fish of younger ages, peaked at age 5 to 6, and then gradually declined as sablefish moved deeper with age. Decreased availability with age may occur because of lower fishing effort in deep water and could have substantial implications for sablefish stock assessments because “dome-shaped” availability influences the reliability of abundance estimates. The area-related recovery pattern was not affected by year-class strength; i.e., there was no significant density-dependent relationship.

An essential component of any mark and recapture study that seeks to estimate fish population abundance, exploitation rates, or migration rates from tagging data is the tag-reporting rate. We obtained tag-reporting rates for the sablefish Anoplopoma fimbria fishery during 1980–1998 by comparing tag returns in the fishery to tag returns from a scientific survey where all tag recoveries were assumed to be reported. Analytical formulae were derived for the measurement error associated with the estimates. When pooled over geographic areas or years, estimates of reporting rates were reasonably precise with coefficients of variation (CVs) usually less than 25%. Reporting rates were highest in the central (0.385) and eastern (0.315) Gulf of Alaska, intermediate in the western Gulf of Alaska (0.269), and lowest in the Aleutians (0.174) and Bering Sea (0.169). Rates pooled over all areas increased from lows of 0.102–0.248 in 1980–1982 to a peak of 0.465 in 1985 before declining to 0.199 in 1986 and 0.157 in 1987. The reporting rate increased gradually and fluctuated between 0.376 and 0.450 since 1995. The increase in reporting in 1995 was coincidental with the implementation of the Individual Fishing Quota (IFQ) system. The linear increase in reporting rates during 1986–1998 was significant. Factors that may have influenced the reporting rate were the number of tags available for recovery, the length of the commercial fishing season, the presence of scientific observers on commercial vessels, and the tag reward program. Pooled over all years and areas the tag-reporting rate has been 0.276 with a CV of 4.2%.