RESOURCE ECOLOGY & FISHERIES MANAGEMENT (REFM) DIVISION
(SAFE Summaries cont.)

BSAI Other Flatfish Complex

The "other flatfish" assessment incorporated biomass estimates from the 2002 EBS trawl survey and the 2002 AI trawl survey. The 2002 biomass EBS and AI survey estimates for other flatfish species were 97,938 t and 8,801 t, respectively. In 2002, the species composition of the other flatfish complex in the EBS survey was Dover sole (<1%), rex sole (27%), longhead dab (10%), Sakhalin sole (<1%), starry flounder (61%), and butter sole (2%). Relative to 2001, other flatfish increased.

In 2002, the stock assessment author reexamined the harvest policy for the other species complex. In previous assessments, the F_40% estimate for flathead sole was used as a proxy exploitation rate. It was noted that starry flounder was the dominant species within the complex. The life history characteristics of starry flounder differ from flathead sole. This finding suggested that using the flathead sole F_40% harvest rate as a proxy for the other species complex could not be supported. Based on this analysis, the recommended ABC and OFL for other flatfish species was based on a Tier 5 criteria. The recommended 2003 ABC and OFL for the other flatfish complex were 14,691 t, and 19,588 t respectively.
 

BSAI Pacific Ocean Perch

Pacific ocean perch (POP) are managed as a single BSAI population. In 2002, the POP assessment incorporated new information on fishery harvest levels, fishery age, and length compositions and biomass estimates from the AI trawl survey. The 2002 biomass estimate for POP from the AI survey was 468,588 t, an 8% decrease from the 2000 survey estimate. Reliable estimates of B_40%, F_40%, and F_35% exist for this stock; therefore, the stock qualified for management under Tier 3 of the BSAI Groundfish FMP. The updated point estimates of B_40%, F_40%, and F_35% from the present assessment are 137,390 t, 0.048, and 0.057, respectively. Projected spawning biomass for 2003 is 135,000 t, placing POP in the EBS in sub-tier "b" of Tier 3. The maximum F_ABC value allowed under Tier 3b is 0.047. Projected harvesting at a fishing mortality rate of 0.047 gives a 2003 catch of 15,071 t, which is the recommended ABC. The OFL fishing mortality rate is 0.056 under sub-tier 3b. Projected harvesting at a fishing mortality rate of 0.056 gives a 2003 catch of 17,856 t, the recommended OFL. Model projections indicate that this stock is neither overfished nor approaching an overfished condition.

BSAI Other Red Rockfish

The other red rockfish complex is composed of northern, rougheye, and shortraker rockfish. For management purposes, these species are managed in two groups, Northern and Shortraker/Rougheye.

For each species, the F_ABC was set at the maximum value allowable under Tier 5, which is 75% of M. Accepted values for M are rougheye rockfish-0.025; shortraker rockfish-0.030; and northern rockfish-0.060. Multiplying these rates by the best estimates of species-specific biomass gives the 2003 ABCs as shown in Table 2. The 2003 OFL levels are shown in Table 3.

Other Rockfish

Assessment authors conducted a detailed examination of the available information for assessment of the status of the "other rockfish" complex. Catch distribution maps were created for the light dusky rockfish and shortspine thornyhead complex. In 2002, sharpchin rockfish were added to the other rockfish complex. Eight species have been confirmed or tentatively identified in catches from the BSAI. These species include sharpchin rockfish, dark dusky rockfish, light dusky rockfish, harlequin rockfish, red banded rockfish, redstripe rockfish, yelloweye rockfish, and shortspine thornyhead. The assessment incorporated new biomass estimates from the EBS shelf and slope surveys and the AI trawl survey. The recommended ABCs and OFLs for 2003 are shown in Table 4.
 

AI Atka Mackerel

The 2002 AI Atka mackerel stock assessment incorporated new catch data, the 2001 fishery age composition, and the 2002 AI survey biomass estimates. The AI trawl survey biomass estimate was 772,798 t, a 51% increase from the 2000 estimate. Age composition data indicate that the 1998 year class may be above average.

The 2002 assessment was implemented using AD Model Builder as a modeling platform. Selectivity was allowed to vary annually. The revised selectivity patterns resulted in lower historical biomass levels and higher historical fishing mortalities. The SSC has determined that this stock is qualified for management under Tier 3 of the BSAI Groundfish FMP. The updated point estimates of B_40%, F_40%, and F_35% from the present assessment are 177,900 t, 0.66, and 0.84, respectively. Projected female spawning biomass for 2003 is 106,200 t, placing Atka mackerel in sub-tier "a" of Tier 3. The maximum F_ABC value allowable under Tier 3a is F_40% (0.66). Projected harvesting at a fishing mortality rate of 0.66 gives a 2003 catch of 82,800 t, which is the maximum permissible value of ABC under Tier 3a.

The OFL was determined from the Tier 3a formula, where an F_35% value of 0.84 gives a 2003 OFL of 99,700 t. Model projections indicate that this stock is neither overfished nor approaching an overfished condition.
 

BSAI Squid and Other Species Complex

The squid assessment was updated by incorporating new catch information. The 2001 squid catch of 1,810 t was approaching the ABC of 1,970 t. Squid are managed under Tier 6, where the OFL is set equal to the average catch from 1978 through 1995, and ABC is constrained to be no greater than 75% of OFL. The average catch from 1978 through 1995 was 2,624 t. The maximum permissible value of ABC for 2003 therefore is 1,970 t, which is the Plan Team's recommended value.

The "other species" assessment includes sharks, skates, sculpins, and octopi. The assessment was updated by incorporating new catch and survey biomass information from the slope and shelf trawl surveys. For the 2003 fishing year, the author's recommended ABC for the other species complex was calculated as 0.75 times the average catch from 1978 to 1995, or 19,320 t. The author's recommended overfishing level for the other species complex in the year 2003 was calculated as the average catch from 1978 to 1995, or 25,760 t. The rationale for a Tier 6-based ABC and OFL is that there are no reliable estimates of natural mortality for a species complex containing animals with such extremely diverse life histories. The Plan Team recommends setting F_ABC for sculpins and skates at the maximum allowable under Tier 5, which is 75% of M. The NPFMC SSC recommended that this strategy be reviewed.

>>>continued

AFSC Quarterly
Research Reports
Oct.-Dec. 2002