Status of the Pacific Mackerel resource during 1996 management recommendations for the fishery

The California fishery for Pacific mackerel (Scomber japonicus) has declined precipitously since 1990. Statewide landings during 1995 continued the downward trend, and totaled only 9,185 short tons. During the last few years, the principal cause of reduced catches has been low biomass and poor availability on the traditional fishing grounds in southern California waters. Cannery closures since 1993 may have also affected demand. Several sources of information are available on the status of the Pacific mackerel stock, all of which suggest a decline in stock biomass compared to the late 1970's and 1980's. Landing statistics, available since 1978 for both the U.S. and Mexican fisheries, show reduced catches during recent years. Catch rates for the southern California Commercial Passenger Fishing Vessel (CPFV) fleet have also shown declining trends since the 1970's. Other fishery- independent data from spotter pilot aerial observations and California Cooperative Oceanic Fisheries Investigations (CalCOFI) ichthyoplankton surveys indicate lower abundance compared to the early 1980's. We used a tuned virtual population analysis (VPA) model called ADEPT to estimate Pacific mackerel biomass. The model finds the best statistical fit between fishery-based, age-structured biomass estimates and other data from aerial observations, plankton surveys, CPFV catch data, and a spawner-recruit relation. Based on the estimated number of fish in each year class during the last quarter of 1995 (including the 1995 year class), and using certain assumptions for expected fishing mortality during the first half of 1996, we project that the Pacific mackerel biomass will be 52,000 tons at the beginning of the 1996/97 fishing season, on July 1,1996. There is a large degree of uncertainty in our 1996 biomass estimate because the 1995 year class (fish of age one) comprises most of the biomass. The Fish and Game Code specifies that when the biomass is between 20,000 and 150,000 tons, the season's quota shall be 30 percent of the total biomass in excess of 20,000 tons. Using that formula and our projection for July 1,1996, we recommend a commercial fishery quota of 9,600 tons for the 1996/97 fishing season. (26pp.

Status of the Pacific sardine (Sardinops sagax) resource and fishery

California Fish and Game Code states that the annual sardine quota can be set at a level greater than 1,000 tons, providing that the level of take allows for continued increase in the spawning population. The primary goal of management as directed by the Code is rehabilitation of the resource, with an added objective of maximizing the sustained harvest. We estimate the sardine population size to have been 353,000 short tons on July 1, 1995. Our estimate was based on output from an integrated stock assessment model called CANSAR (Deriso 1993). CANSAR is a forward-casting age-structured analysis using fishery-dependent and fishery-independent data to obtain annual estimates of sardine abundance, year-class strength and age specific fishing mortality for 1983 through the first semester of 1995. CANSAR couples a simulation model with sardine population dynamics. Non-linear least-squares criteria are used to tune the model to match catch-at-age data and other indices of sardine abundance. To calculate the 1996 fishery quota, we used the harvest formula selected as the preferred option in the draft Coastal Pelagic Species-Fishery Management Plan (CPS-FMP). That formula has undergone extensive scientific and user-group review as part of the Pacific Fishery Management Council's (PFMC) CPS-FMP adoption process and has the endorsement of the fishing industry and the scientific community. Use of this formula will result in a reduced fishing mortality rate compared to the formula used to calculate the quota in 1995. We conclude that it is particularly important to reduce fishing mortality for 1996 because the rates may have been excessive in recent years, especially for older aged sardines. Accordingly, we recommend a 1996 sardine harvest quota of 35,000 short tons. (21pp.

Status of the Pacific Mackerel resource during 1997 and management recommendations for the fishery

Based on a California Department of Fish and Game (CDFG) projected biomass estimate of 91,200 metric tons for July 1, 1997, the recommended commercial fishery quota for the 1997/98 fishing season is 22,000 metric tons. Age-specific abundance for 1996 was estimated using output from a stock assessment model called ADEPT and certain assumptions about growth and fishing mortality during the first half of 1997. In this year's assessment, abundance estimates made by ADEPT were expanded back in time to cover the 68-year period of 1929 through 1996. The commercial fishery quota recommendation is based upon the prescribed harvest formula for Pacific mackerel that is specified in the California Fish and Game Code. Several sources of information are available for the Pacific mackerel stock, all of which suggest a smaller biomass than was present in the 1980's. Landings from both California and Ensenada, Mexico have sharply decreased and catch rates from the southern California Commercial Passenger Fishing Vessel (CPFV) fleet have declined. Fishery-independent indices of abundance from aerial spotter observations and California Cooperative Oceanic Fisheries Investigations (CalCOFI) ichthyoplankton surveys show similar trends. The 1997 biomass estimate is higher than last year's estimate of 47,160 metric tons because data added to the model this year increased abundance for fish of 1994 and older year classes (age 2+). This year's results indicate there were more fish in the older year classes than estimated in previous assessments. (27pp.

Stock assessment and management recommendations for Pacific sardine (Sardinops sagax) in 1997

The primary goal of sardine management as directed by the California Fish and Game Code is rehabilitation of the resource with an added objective of maximizing sustained harvest. Accordingly, the Code states that the annual sardine quota can be set at an amount greater than 1,000 tons, providing that the level of take allows for continued increase in the spawning population. We estimated the sardine population size to have been 464,000 short tons on July 1, 1997. Our estimate was based on output from a modified version of the integrated stock assessment model called CANSAR (Deriso et al. 1996). CANSAR is a forward-casting, age-structured analysis using fishery-dependent and fishery-independent data to obtain annual estimates of sardine abundance, year-class strength and age-specific fishing mortality for 1983 through the first semester of 1997. Non-linear least-squares criteria are used to find the best fit between model estimates and input data. Questions about stock structure and range extent remain major sources of uncertainty in assessing current sardine population biomass. Recent survey results and anecdotal evidence suggest increased sardine abundance in the Pacific Northwest and areas offshore from central and southern California. It is difficult to determine if those fish were part of the stock available to the California fishery. In an attempt to address this problem, the original CANSAR model was reconfigured into a Two-Area Migration Model (CANSAR-TAM) which accounted for sardine lost to the areas of the fishery and abundance surveys due to population expansion and net emigration. While the model includes guesses and major assumptions about net emigration and recruitment, it provides an estimate which is likely closer to biological reality than past assessments. The original CANSAR model was also used and estimates are provided for comparison. Based on the 1997 estimate of total biomass and the harvest formula used last year, we recommend a 1998 sardine harvest quota of 48,000 tons for the California fishery. The 1998 quota is a decrease of 11% from the final 1997 sardine harvest quota for California of 54,000 tons. (55pp.

Status of the Pacific mackerel resource and fishery in 1998

Based on the projected Pacific mackerel biomass estimate of 132,500 tons for July 1, 1998, the commercial fishery quota for the 1998/99 fishing season was recommended and set at 33,700 short tons. The 1998 biomass was estimated using output from a stock assessment computer model called ADEPT and certain assumptions about fishing mortality during the first half of 1998. Several important changes were made to improve our assessment during 1998. The assessment model was changed from a quarterly to an annual one and now covers sixty-nine years of fishery data. New indices of relative abundance were added to the analysis to account for changes in mackerel biomass off central and northern California. The July 1, 1998, biomass estimate is slightly higher than last year's CDFG estimate of 101,000 tons for 1997. This year's results indicate there were more fish in the older year classes than previously estimated. (62pp.

Stock assessment of Pacific sardine for 1998 with management recommendations for 1999

The primary goal of sardine management as directed by the California Fish and Game Code is rehabilitation of the resource with an added objective of maximizing sustained harvest. Accordingly, the Code states that the annual sardine quota can be set at an amount greater than 1,000 tons, providing that the level of take allows for continued increase in the spawning population. We estimated the sardine population size within the range of the fishery and survey data (Ensenada, Baja California to San Francisco, California) to have been 1,182,881 short tons on July 1, 1998. Our estimate was based on output from a modified version of the integrated stock assessment model called CANSAR (Deriso et al. 1996). CANSAR is a forward-casting, age-structured analysis using fishery-dependent and fishery-independent data to obtain annual estimates of sardine abundance, year-class strength and age-specific fishing mortality for 1983 through the first semester of 1998. Non-linear least-squares criteria are used to find the best fit between model estimates and input data. Questions about stock structure and range extent remain major sources of uncertainty in assessing current sardine population biomass. Recent survey results and anecdotal evidence suggest increased sardine abundance in the Pacific Northwest and areas offshore from central and southern California. It is difficult to determine if those fish were part of the stock available to the California fishery. Last year, in an attempt to address this problem, the original CANSAR model was reconfigured into a Two-Area Migration Model (CANSAR-TAM; Hill et al. 1998) which accounted for sardine lost to the areas of the fishery and abundance surveys due to population expansion and net emigration. While the model includes guesses and major assumptions about net emigration and recruitment, it provides an estimate which is likely closer to biological reality than original CANSAR assessments. Corroborative results from a new, preliminary sardine stock assessment model, 'SAM', are also presented in this report. Based on the 1998 estimate of age 1+ biomass within the range of the fishery and survey data, and a proposed harvest formula in the draft Coastal Pelagic Species Fishery Management Plan (Amendment 8), we recommend a 1999 sardine harvest quota of 132,800 tons for the California fishery. The 1999 quota is a significant increase from the final 1998 sardine harvest quota for California of 48,000 tons. (93pp.