Evaluation of Design-Based Estimators in Federal Groundfish Fisheries off Alaska

Cahalan, Jennifer A.; Gasper, Jason R.; Mondragon, Jennifer

doi:10.4027/fbgics.2015.09

Cited by 14 publications

(18 citation statements)

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“…Target species is determined by the dominant species by weight landed following a given vessel trip and is not a factor in assigning observers to vessels (Cahalan et al. ).…”

Section: Methodsmentioning

confidence: 99%

Lessons from seabird conservation in Alaskan longline fisheries

Melvin

Dietrich

Suryan

et al. 2019

Conservation Biology

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Although bycatch of seabirds and other long‐lived species is a critical conservation issue in world fisheries, case studies documenting significant reductions in the mortality of these low‐productivity species in a fishery are rare. We studied progress toward seabird conservation in the Alaskan longline fisheries, one of the largest and most diverse demersal fisheries. We generated annual seabird bycatch rates in 4 target fisheries and all fisheries combined from 23 years of fisheries observer data. We used 0‐inflated negative binomial models to evaluate variables influencing seabird bycatch per unit effort (BPUE) in 2 target fisheries. Following adoption of streamer lines, at first voluntarily and then mandatorily, seabird BPUE was reduced by 77–90%, preventing mortality of thousands of birds per year. Despite this, BPUE increased significantly in 2 of 4 target fisheries since streamer lines were adopted. Although night setting yielded significant reductions (74–97%) in seabird BPUE and significant increases (7–11%) in fish catch per unit effort over daytime setting, nighttime setting increased the BPUE of Northern Fulmar () by 40% and nontarget fish species by 5–17%. Thus, best practices to prevent seabird mortalities in longline fisheries varied by species assemblage and fishery. Our results inform global efforts toward fisheries bycatch reduction by illustrating that successful conservation requires fishery‐specific solutions, strong industry support, constant vigilance in analysis and reporting observer data, and ongoing outreach to fleets, especially to vessels with anomalously high BPUE.

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“…Target species is determined by the dominant species by weight landed following a given vessel trip and is not a factor in assigning observers to vessels (Cahalan et al. ).…”

Section: Methodsmentioning

confidence: 99%

Lessons from seabird conservation in Alaskan longline fisheries

Melvin

Dietrich

Suryan

et al. 2019

Conservation Biology

View full text Add to dashboard Cite

show abstract

“…The observer determined how to best randomize their sampling of the catch for species composition for each sampled haul by dividing the catch for the haul into defined sampling units, determining number of units they are able to collect, and deciding how to randomize the collection of those samples (Cahalan et al, 2014;AFSC, 2011). Sample units are typically defined in terms of catch weight or volume, e.g.…”

Section: Standard Sampling Methodsmentioning

confidence: 99%

“…In contrast, in Alaska trawl fisheries, the volume of catches and discards often exceeds amounts that can be weighed directly by the observer. On many vessels, estimates of both retained catch and discarded catch are based on observer data, particularly on larger factory trawlers (Cahalan et al, 2014). While on vessels that deliver their catches to shoreside processors (catcher vessels, CVs), estimates of catch discarded at sea are based on observer data, and retained catches are based on industryreported landings data.…”

Section: Introductionmentioning

confidence: 99%

A field test of fisheries observer sampling methods for estimation of at-sea discards

Cahalan

Faunce

Bonney³

et al. 2016

Fisheries Research

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a b s t r a c tEstimation of at-sea discards is an issue that has received considerable attention worldwide. With this increasing focus, there is a need for greater precision of weight estimates for less common and fisherylimiting species. While one solution is to mandate full (100%) observer coverage to reduce uncertainty in estimation at the trip level, variance from on-deck sampling methods (e.g. within-haul) should also be properly addressed. Commercial fishing vessels are not perfect sampling platforms and all sampling methods suffer from implementation issues that potentially impact the quality of the data collected and the resulting estimates. We conducted a cooperative study with industry to evaluate two observer sampling methods on trawl vessels delivering their catch to shoreside processors. The alternative observer sampling method that targets the portion of the haul that would be discarded directly at-sea, relying on shoreside reports of retained catch to generate total catch estimates, was tested against the standard methods currently used by the NMFS North Pacific Groundfish and Halibut Observer Program that sample the entire catch, both retained and discarded portions (combined). Methods were tested simultaneously by deploying two observers to sample each haul on study trips within three Gulf of Alaska trawl fisheries that varied widely in amount and species composition of discards: Rockfish Program, arrowtooth flounder, and shallow water flatfish. Although the alternative method was successfully implemented in two of the three fisheries, logistical constraints decreased sampling effectiveness in the third. In some situations, observers were unable to collect multiple samples under both methods, preventing variance estimation. This occurred more often for the observer using standard methods. Detection of less common and rare species was higher using the alternative sampling method. Discard estimates from the two methods were found to be significantly different in two of the fisheries examined (Rockfish Program and arrowtooth flounder). Discard estimates under the alternative method tended to have smaller variances than for the standard method, although this was not universally the case. These results provide an important comparison of the relative performance of different on-deck sampling methods under varying catch conditions and fisheries.

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“…The surveys would be conducted by the commercial fishers, certified by AFSC acousticians, and a multi-species, overall biomass limit would be set for the surveyed area prior to the fishery opening. This management system was thought possible because 1) there is a well-established mechanism for setting allowable catch limits [12], 2) a robust catch accounting system in place [13], and 3) the commercial echosounders used by fishers and the scientific echosounders used by the AFSC to survey pollock are produced by the same company and the echosounder hardware is nearly identical. Data from the commercial and scientific echosounders have been shown to be comparable when the echosounders are properly calibrated and data properly processed [14].…”

Section: Real-time Local Cooperative Managementmentioning

confidence: 99%

“…Data from the commercial and scientific echosounders have been shown to be comparable when the echosounders are properly calibrated and data properly processed [14]. The proposed cooperative fisheries management system would rely on the integration of the catch monitoring and accounting systems already in place in the federal groundfish fisheries off Alaska [12,13] with local cooperative acoustic survey biomass estimates (Fig. 2).…”

Section: Real-time Local Cooperative Managementmentioning

confidence: 99%

Exploring local fishery management through cooperative acoustic surveys in the Aleutian Islands

2018

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A B S T R A C TAn alternate management system is introduced which uses seasonal and spatially explicit multi-species quotas generated from small-scale cooperative fishery acoustic surveys to manage the Aleutian Islands walleye pollock (Gadus chalcogrammus) fishery while limiting impacts on the endangered Western stock of Steller sea lions (Eumetopias jubatus). This is a novel collaboration among scientists, industry, and Alaska Natives considering a cooperative management approach. The proposed system integrates the catch monitoring and accounting systems already in place in the federal groundfish fisheries off Alaska with cooperative acoustic survey biomass estimates to facilitate more refined spatial and temporal fishery management decisions. Conditions were examined under which such a system could operate successfully and results from field work conducted to assess technical requirements were discussed. During field trials biomass estimates from each survey were produced within 24-h of survey completion. This suggests spatial abundance estimates can be available in a timely manner for managing local fisheries. The proposed management system was found feasible and relatively easy to initiate because of highly motivated and cooperative industry partners, a well-established mechanism for setting allowable catch limits, and a robust catch accounting system already in place. In addition, high quality commercial echosounders required for this system are currently used by industry and, with proper controls on calibration and survey design, produce biomass estimates of sufficient quality. The application of this approach beyond this case study is also discussed for managing fisheries worldwide where fine temporal and spatial scale management could benefit the conservation of other protected species.

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Evaluation of Design-Based Estimators in Federal Groundfish Fisheries off Alaska

Cited by 14 publications

References 0 publications

Lessons from seabird conservation in Alaskan longline fisheries

Lessons from seabird conservation in Alaskan longline fisheries

A field test of fisheries observer sampling methods for estimation of at-sea discards

Exploring local fishery management through cooperative acoustic surveys in the Aleutian Islands

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