Estimating movement and abundance of Atka mackerel (Pleurogrammus monopterygius) with tag–release–recapture data

Abstract

A mark-recapture experiment was conducted in Seguam Pass, Alaska, to estimate local Atka mackerel (Pleurogrammus monopterygius) abundance and to evaluate the efficacy of trawl exclusion zones around Steller sea lion (Eumetopias jubatus) rookeries. Atka mackerel were found in dense aggregations near the Aleutian Islands where they are a major prey item of endangered Steller sea lions. In 1999, 1375 tagged fish were released and a biomass of 76 679 metric tonnes (t) was estimated outside a trawl exclusion zone using a simple Petersen model. In 2000, 8773 tagged fish were released and the estimated biomasses were 117 900 t inside and 82 057 t outside the trawl exclusion zones using an integrated tagging model. Movement into the open zone was small after 107 days (0.6%), whereas movement from the open area was potentially large but highly uncertain after 107 days (81%). Our model suggests that trawl exclusion zones in Seguam Pass are effective in separating a large biomass of potential prey for Steller sea lions from the immediate effects of local fisheries. Atka mackerel do not appear to move substantially outside their local aggregations (<70 km), and they show strong habitat preferences within their local home ranges. In one instance, fish released in an area of low Atka mackerel abundance returned to their capture location about 2 miles away. Thus individual Atka mackerel may have an affinity for particular areas within their home range, perhaps resulting from adaptations to local oceanic conditions along the Aleutian Island archipelago.

Sex-biased dispersal and growth in sablefish (Anoplopoma fimbria) in the northeastern Pacific Ocean

“…3 Relationship between distance moved per month and growth increment deviation calculated as ln(ΔL/Δ b L), where ΔL is the observed growth increment and Δ b L is the expected growth increment obtained from the von Bertalanffy growth models M 1 (see Table 1), for male and female sablefish. Regression line, growth increment deviation=0.28 log (movement distance + 1) -0.30, r=0.18 movement (Hunt et al 1999;McDermott et al 2005), but little is known about the sex-biased dispersal patterns in fishes. Beamish and McFarlane (1988) indicated that adult sablefish show little movement behavior, but our long-term data indicate that adult sablefish undergo long-distance movement.…”

Oceanography and ecology of the Aleutian Archipelago: spatial and temporal variation

“…, 2005; Logerwell et al. , 2005; McDermott et al. , 2005), the biology and ecology of sea lions (Call and Loughlin, 2005; Fadely et al.…”

Highly Discordant Nuclear and Mitochondrial DNA Diversities in Atka Mackerel

“…Adult Atka mackerel do not appear to be highly migratory (McDermott et al 2005), but the highly protracted spawning-brooding reproductive cycle (up to 6 months) and planktonic larval phase (up to 1 year), combined with vigorous current systems in the Gulf of Alaska and Bering Sea, suggest that long-distance dispersal is likely (Gorbunova 1962;Kendall and Dunn 1985) to impede genetic divergence. The Alaskan populations examined in the present study inhabit two major current systems that are partially isolated by the Alaska Peninsula and Aleutian Islands chain.…”

“…Newly hatched larvae are neustonic (Kendall and Dunn 1985) and develop in pelagic habitats for 1 year before recruiting into demersal populations as juveniles. Tagging results indicate that adults form local aggregations and generally move less than 70 km (McDermott et al 2005).…”