Move it or lose it: movement and mortality of sablefish tagged in Alaska

Abstract

A basic step in understanding the dynamics of a fish population is to quantify movement and mortality rates. Conventional mark-recapture experiments have provided the foundation for studies on animal movement, particularly for fish. Previous studies have shown rapid mixing of sablefish (Anoplopoma fimbria) among fishery regulatory areas, with the pattern of movement related to fish size. Over 300 000 tag releases in Alaska and over 27 000 tag recoveries from 1979 to 2009 were analyzed. We used a Markov model to quantify annual movement probabilities among areas for three size groups of sablefish. The negative-binomial likelihood was used to model the tag-recovery data because of significant overdispersion. Annual movement probabilities were high, ranging from 10% to 88% depending on area of occupancy at each time step and size group. Overall, movement probabilities were very different between areas of occupancy and moderately different between size groups. Estimated annual movement of small sablefish from the central Gulf of Alaska had the reverse pattern of a previous study, with 29% moving westward and 39% moving eastward. Movement probabilities also varied annually, with decreasing movement until the late 1990s and increasing movement until 2009. Year-specific magnitude in movement probability of large fish was highly negatively correlated with female spawning biomass estimates from the federal stock assessment. Mean mortality estimates from time at liberty were similar to the federal stock assessment. Incorporating these tag-recovery and movement data into a fully age-structured spatial stock assessment model will inform harvest apportionment strategies to conserve spawning biomass and maximize future yields.

Spatial variation in exploited metapopulations obscures risk of collapse

“…, Hanselman et al. , Rand et al. ) can, given ranges reported, access the geographic area covered by the stock (Table , see Data: Home_Range_Literature).…”

A Comparison of Methods for Classifying Female Sablefish Maturity and Skip Spawning Outside the Spawning Season

“…However, this is near the center of the distribution of Sablefish in Alaska, Sablefish are highly migratory (they are not likely to have discrete stocks with differencing life history) (Hanselman et al 2014), and it is still a broad geographic area. If using samples from the summer survey, the microscopic results indicate that the most reliable maturity classifications will come from the last leg of the survey, using either the standardized macroscopic or microscopic methods or a combination of the two.…”

“…In Alaska, fish age 2+ reside in waters approximately 150-1,000 m deep along the continental slope, in cross-shelf gullies, and in nearshore, deep channels (Rutecki et al 2016). Sablefish are highly migratory and are managed as a single population in Alaska (Hanselman et al 2014). Sablefish are highly migratory and are managed as a single population in Alaska (Hanselman et al 2014).…”

A test of the detection range of acoustic transmitters and receivers deployed in deep waters of Southeast Alaska, USA

“…Sablefish in US Federal waters are currently managed by US National Marine Fisheries Service (NMFS) as a single population [1] based largely on conventional tagging data and genetic evidence [2,3] that suggest considerable mixing throughout offshore waters from the Aleutian Islands and eastern Bering Sea and southward to the Alaskan panhandle. In contrast, analyses of tagging data [1,4] have indicated only limited exchange between this stock component and the state-managed waters of Southeastern Alaska [1], and so the latter is managed separately using closed-population mark-recapture-based abundance estimates [5].…”

“…Sablefish in US Federal waters are currently managed by US National Marine Fisheries Service (NMFS) as a single population [1] based largely on conventional tagging data and genetic evidence [2,3] that suggest considerable mixing throughout offshore waters from the Aleutian Islands and eastern Bering Sea and southward to the Alaskan panhandle. In contrast, analyses of tagging data [1,4] have indicated only limited exchange between this stock component and the state-managed waters of Southeastern Alaska [1], and so the latter is managed separately using closed-population mark-recapture-based abundance estimates [5]. For Pacific halibut, extensive mixing suggested by passive integrated transponder (PIT) tagging programs [6] has served to justify coastwide assessment modeling [7] and conventional tagging data have been used to estimate seasonal cross-boundary migration rates [8] that are important to consider when discussing fishery season dates (sensu [9]).…”