We analyzed allozymes from 13 collections of lingcod Ophiodon elongatus representing over 1,100 individuals throughout most of the species' range from Alaska to central California. Data were gathered from 41 presumptive gene loci of which 19 loci (46%) were polymorphic (Po.99 criterion, whereby the frequency of the most common allele is 0.99 or less in at least one collection). Average observed heterozygosity was 0.050 (SE, 0.001). Significant differences in genotype frequencies were found between sexes at the AH-2* locus for aconitate hydralase. Although lingcod populations are genetically similar throughout the range, significant allele frequency differences suggest that lingcod in Puget Sound are partially isolated from those along the open coast.

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Using mark-recapture and fishery data from 1986 to 1992, I estimated abundance, survival, mortality, net loss, and catchability of lingcod Ophiodon elongatus in the nearshore waters of Cape Flattery, Washington. I used an open-population estimation model, which employed a multiple-year tag-release experimental design and an exploitation-based (sport fishery) tag-recapture process. The results indicated a high rate of population turnover (recruitment and emigration). Lingcod abundance appeared to vary in response to recruitment and ranged from 114,000 to 208,000 fish annually. Annual survival (5) ranged from 34 to 81%. Total instantaneous mortality (Z) was partitioned into sport fishing mortality (F) and a net loss term (L), which included both natural mortality and emigration; F ranged from 0.08 to 0.13 and L ranged from O.I I to 0.96. I propose that emigration is the best explanation for the high loss rates observed. Average catchability (q) declined by 60% from April to August, suggesting that reduced availability occurred seasonally at the nearshore area in late spring and summer. The results indicate the dynamic nature of the lingcod population near shore and the importance of modeling this stock as an open population for fisheries management.

Movement, size selectivity, and fishing mortality parameters of lingcod Ophiodon elongatus were estimated for the sport and trawl fisheries off Washington by using mark-recapture data from 1991 to 1994. Parameters were estimated with a multiple-year tag release sample design by maximizing the likelihood of the observed tag recoveries via the method of tuned simulation. The results confirm the open nature of the coastal lingcod population: lingcod found near shore became vulnerable to the trawl fishery off shore, though very few lingcod found off shore became vulnerable to the sport fishery near shore. The relatively greater selectivity of small female lingcod estimated by this study, compared with estimates from a previous catch-at-age analysis, suggests the possibility of undocumented discard mortality in the trawl fishery. Previous mark-recapture fishery interaction studies required independent estimates of fishing mortality to estimate movement rates. This study shows that both fishing mortality and selectivity can be estimated for a twofishery interaction model with 3 years of tag releases and 4 years of tag recaptures when sufficient numbers of tag recoveries are available for all strata.

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Schools of fish can cause interference for long-range active sonars. The degree of interference depends heavily on the target strengths of the schools. However, there are few measurements and limited modeling of school target strengths in the frequency ranges of these sonars. During the summers of 2009 through 2013, a comprehensive set of measurements of the characteristics of Pacific sardine schools was collected off the west coast of the United States. This data set has enabled model estimates of the target strength distributions of these schools to be made at frequencies between 500 Hz and 10 kHz. This paper describes the sardine school data, its use in the modeling, the modeling procedures, and the target strength distributions obtained. The analysis indicates that, given the rates at which high target strengths occurred at all frequencies of interest, Pacific sardine schools could be a significant source of interference for long-range active sonars operating in their vicinity.