Sablefish mortality associated with whale depredation in Alaska

2017 ◽  
Vol 74 (5) ◽  
pp. 1382-1394 ◽  
Author(s):  
Megan J. Peterson ◽  
Dana Hanselman
Keyword(s):  
Killer Whale ◽  
Stock Assessment ◽  
Sperm Whale ◽  
Statistical Modelling ◽  
Gulf Of Alaska ◽  
Fish Stock ◽  
Physeter Macrocephalus ◽  
Commercial Fishery ◽  
Catch Rates ◽  
The Impact

Killer whale (Orcinus orca) and sperm whale (Physeter macrocephalus) depredation (whales removing or damaging fish caught on fishing gear) can reduce catch rates and decrease the accuracy of fish stock assessments. This study advances our understanding of the impact of whale depredation on the commercial sablefish (Anoplopoma fimbria) fishery in Alaska and evaluates the impact depredation may have on the annual federal sablefish assessment. A statistical modelling approach was used to estimate the whale effect on commercial sablefish fishery catch rates; killer whale depredation was more severe (catch rates declined by 45%–70%) than sperm whale depredation (24%–29%). Total estimated sablefish catch removals 1995–2014 ranged from 1251 t to 2407 t by killer whales in western Alaska management areas and 482 t to 1040 t by sperm whales in the Gulf of Alaska 2001–2014. Including sablefish mortality due to whale depredation on the commercial fishery in the sablefish stock assessment resulted in a 1% reduction in the recommended quota. Accounting for sablefish mortality due to whale depredation in the commercial fishery in the sablefish assessment will occur tandem with correcting for depredation on the annual National Marine Fisheries Service longline survey, the primary survey index used in the assessment.

scholarly journals Killer whale (Orcinus orca) depredation effects on catch rates of six groundfish species: implications for commercial longline fisheries in Alaska

2013 ◽  
Vol 70 (6) ◽  
pp. 1220-1232 ◽  
Author(s):  
Megan J. Peterson ◽  
Franz Mueter ◽  
Dana Hanselman ◽  
Chris Lunsford ◽  
Craig Matkin ◽  
...  
Keyword(s):  
Bering Sea ◽  
Killer Whale ◽  
Temporal Trends ◽  
Gulf Of Alaska ◽  
Orcinus Orca ◽  
Future Research ◽  
Fish Stock ◽  
Anoplopoma Fimbria ◽  
Catch Rates ◽  
Longline Fisheries

Abstract Peterson, M. J., Mueter, F., Hanselman, D., Lunsford, C., Matkin, C., and Fearnbach, H. 2013. Killer whale (Orcinus orca) depredation effects on catch rates of six groundfish species: implications for commercial longline fisheries in Alaska. – ICES Journal of Marine Science, 70: 1220–1232. Killer whale (Orcinus orca) depredation occurs when whales damage or remove fish caught on longline gear. This study uses National Marine Fisheries Service longline survey data from 1998–2011 to explore spatial and temporal trends in killer whale depredation and to quantify the effect of killer whale depredation on catches of six groundfish species within three management areas in Alaska: the Bering Sea, Aleutian Islands and Western Gulf of Alaska. When killer whales were present during survey gear retrieval, whales removed an estimated 54–72% of sablefish (Anoplopoma fimbria), 41–84% of arrowtooth flounder (Atheresthes stomias) and 73% (Bering Sea only) of Greenland turbot (Reinhardtius hippoglossoides). Effects on Pacific halibut (Hippoglossus stenolepis) and Pacific cod (Gadus macrocephalus) were significant in the Western Gulf only with 51% and 46% reductions, respectively. Overall catches (depredated and non-depredated sets) for all groundfish species significantly impacted by killer whale depredation were lower by 9–28% (p < 0.05). Effects on shortspine thornyhead (Sebastolobus alascanus) catches were not significant in any management area (p > 0.05). These results provide insight into the potential impacts of killer whale depredation on fish stock abundance indices and commercially important fisheries in Alaska and will inform future research on apex predator–fisheries interactions.

scholarly journals A modelling approach to evaluate the impact of fish spatial behavioural types on fisheries stock assessment

2018 ◽  
Vol 76 (2) ◽  
pp. 489-500 ◽  
Author(s):  
Josep Alós ◽  
Andrea Campos-Candela ◽  
Robert Arlinghaus
Keyword(s):  
Stock Assessment ◽  
Fishing Effort ◽  
Fish Stock ◽  
Catch Per Unit Effort ◽  
Wide Range ◽  
Stock Assessments ◽  
Theoretical Predictions ◽  
Behavioural Types ◽  
Catch Rates ◽  
The Impact

Abstract Spatial behavioural types (SBTs) arise from between-individual differences in behavioural traits that foster spatial behavioural patterns that are consistent over time and ecological contexts. Fish stocks are regularly assessed using catch per unit effort (CPUE) as input data that may non-linearly co-vary with the underlying abundance (N) of the exploited stock when SBT affect catchability. We hypothesized that SBT promote characteristic changes in catchability within harvesting seasons that affect catch rates and in turn catch-based fish stock assessments. To test this hypothesis, we developed a spatially explicit agent-based simulation where we measured encounters between fish and fishers and estimated the shape of the CPUE–N relationship. We ran the simulation in a prototypical fish–fisher encounter-leads-to-catch-type fishery and systematically studied outcomes in the presence or absence of SBTs. It was revealed that the existence of SBTs leads to CPUE inevitably declining faster than N (a process known as hyperdepletion) when compared with a simulation lacking SBTs. This finding was consistent in a wide range of fishing effort scenarios. The emergent hyperdepletion of catch rates was caused by fast and behavioural-selective exploitation of vulnerable SBT that encompassed the mobile component of the fish stock. The theoretical predictions received support from field data from a coastal recreational fishery. Our work suggests that the consideration of SBT when interpreting trends in CPUE data may notably improve stock assessments by providing a more reliable CPUE–N relationship.

scholarly journals Testing a passive deterrent on longlines to reduce sperm whale depredation in the Gulf of Alaska

2015 ◽  
Vol 72 (5) ◽  
pp. 1667-1672 ◽  
Author(s):  
Victoria O'Connell ◽  
Janice Straley ◽  
Joe Liddle ◽  
Lauren Wild ◽  
Linda Behnken ◽  
...  
Keyword(s):  
Sperm Whale ◽  
Gulf Of Alaska ◽  
Primary Objective ◽  
Collaborative Effort ◽  
Physeter Macrocephalus ◽  
Anoplopoma Fimbria ◽  
Acoustic Data ◽  
The Individual ◽  
And Control ◽  
Individual Fishing Quota

Abstract In Alaska, sperm whale (Physeter macrocephalus) depredation on longline sets has increased since implementation of the Individual Fishing Quota programme in 1995. A collaborative effort (SEASWAP) between longliners, scientists, and managers has undertaken research to evaluate this depredation with a primary objective to develop and test a passive deterrent that would reduce depredation without reducing catch rate of sablefish (Anoplopoma fimbria). Commercial longliners, fishing for their own sablefish quotas during the regular season, deployed beaded gear (25 mm lucite beads attached to gangions) with control gear and set recorders to collect acoustic data. Beaded and control gear were randomly assigned by skate quad (672 hooks) with 5 quads in each longline set. Acoustic recorders were used to document sperm whale creak–pause events, representative of depredation of the longline gear. Although there were more sablefish per skate quad on the beaded gear and there was a decrease in depredation events on the beaded gear compared with the control, neither effect was significant (p = 0.205 and 0.364, respectively). The SEASWAP project is testing other deterrent strategies including gear modifications and the establishment of a sighting network to improve avoidance.

scholarly journals “The Elephant in the Room”: Exploring Natural Mortality Uncertainty in Statistical Catch at Age Models

2020 ◽  
Vol 7 ◽  
Author(s):  
Alessandro Mannini ◽  
Cecilia Pinto ◽  
Christoph Konrad ◽  
Paraskevas Vasilakopoulos ◽  
Henning Winker
Keyword(s):  
Stock Assessment ◽  
Assessment Process ◽  
Sensitivity Analyses ◽  
Fish Stock ◽  
Natural Mortality ◽  
Fishing Mortality ◽  
Food And Agriculture ◽  
Stock Assessments ◽  
The Mediterranean ◽  
The Impact

The natural mortality rate (M) of a fish stock is typically highly influential on the outcome of age-structured stock assessment models, but at the same time extremely difficult to estimate. In data-limited stock assessments, M usually relies on a range of empirically or theoretically derived M estimates, which can vary vastly. This article aims at evaluating the impact of this variability in M using seven Mediterranean stocks as case studies of statistical catch-at-age assessments for information-limited fisheries. The two main bodies carrying out stock assessments in the Mediterranean and Black Seas are European Union’s Scientific Technical Economic Committee for Fisheries (STECF) and Food and Agriculture Organization’s General Fisheries Commission for the Mediterranean (GFCM). Current advice in terms of fishing mortality levels is based on a single “best” M assumption which is agreed by stock assessment expert working groups, but uncertainty about M is not taken into consideration. Our results demonstrate that not accounting for the uncertainty surrounding M during the assessment process can lead to strong underestimation or overestimation of fishing mortality, potentially biasing the management process. We recommend carrying out relevant sensitivity analyses to improve stock assessment and fisheries management in data-limited areas such as the Mediterranean basin.

Sperm whale (Physeter macrocephalus) acoustic ecology at Ocean Station PAPA in the Gulf of Alaska – Part 1: Detectability and seasonality

2019 ◽  
Vol 150 ◽  
pp. 103047
Author(s):  
Nikoletta Diogou ◽  
Daniel M. Palacios ◽  
Sharon L. Nieukirk ◽  
Jeffrey A. Nystuen ◽  
Evangelos Papathanassiou ◽  
...  
Keyword(s):  
Sperm Whale ◽  
Gulf Of Alaska ◽  
Physeter Macrocephalus ◽  
Acoustic Ecology ◽  
Ocean Station Papa

SEASONAL OCCURRENCE OF SPERM WHALE (PHYSETER MACROCEPHALUS) SOUNDS IN THE GULF OF ALASKA, 1999–2001

2004 ◽  
Vol 20 (1) ◽  
pp. 48-62 ◽  
Author(s):  
David K. Mellinger ◽  
Kathleen M. Stafford ◽  
Christopher G. Fox
Keyword(s):  
Sperm Whale ◽  
Gulf Of Alaska ◽  
Seasonal Occurrence ◽  
Physeter Macrocephalus

scholarly journals Cetacean diversity on the Parnaiba Delta, Maranhão state, northeastern Brazil

2008 ◽  
Vol 68 (3) ◽  
pp. 545-551 ◽  
Author(s):  
FA. Magalhães ◽  
CH. Tosi ◽  
RG. Garri ◽  
S. Chellappa ◽  
FL. Silva
Keyword(s):  
Killer Whale ◽  
Current Knowledge ◽  
Sperm Whale ◽  
Distinct Species ◽  
Significant Degree ◽  
Northeastern Brazil ◽  
Brazilian Coast ◽  
Physeter Macrocephalus ◽  
Balaenoptera Acutorostrata ◽  
Estuarine Dolphin

The increase in the research of cetacean surveys on the Brazilian coast has brought new data on the distribution of species never reported before. The present work reviews the current knowledge on cetaceans species and extends this knowledge with an analysis of cetaceans stranded in the Parnaiba Delta, on the coast of Maranhão State, Brazil. The studies on cetacean diversity on the coast of the Parnaíba Delta were made from August 2004 to August 2006. Fourteen strandings were reported, representing six distinct species, such as the estuarine dolphin (Sotalia guianensis), humpback whale (Megaptera novaeangliae), Bryde's whales (Balaenoptera edeni), dwarf minke whale (Balaenoptera acutorostrata), pigmy killer whale (Feresa attenuata), sperm whale (Physeter macrocephalus) and two specimens which have not yet been identified. The significant degree of cetacean diversity in the region shows that the Parnaíba Delta is, possibly, of an important area for cetacean studies in Brasil.

The cetaceans of Aruba, southern Caribbean

2013 ◽  
Vol 94 (6) ◽  
pp. 1161-1174 ◽  
Author(s):  
Jolanda A. Luksenburg
Keyword(s):  
Killer Whale ◽  
Sperm Whale ◽  
Common Dolphin ◽  
Physeter Macrocephalus ◽  
Cetacean Species ◽  
Additional Species ◽  
Pilot Whale ◽  
Stenella Frontalis ◽  
Spotted Dolphin ◽  
Delphinus Capensis

Aruba is one of the most densely populated islands in the Caribbean. However, very little is known about its cetaceans. In 2010 and 2011, a total of 19721 km (1686 h) boat-based surveys over nearshore transects resulted in 117 positively-identified sightings comprising eight species. New records are also added for one of three previously-documented species. Five additional species were documented from strandings or reports by others. This brings the total number of cetacean species identified in Aruban waters to 16, of which nine are authenticated here for the first time. Atlantic spotted dolphin (Stenella frontalis (N = 59) and bottlenose dolphin (Tursiops truncatus) (N = 33) were the most frequently observed species, with sightings of both year-round, followed by spinner dolphin (S. longirostris) and false killer whale (Pseudorca crassidens). Additional species recorded are pantropical spotted dolphin (S. attenuata), striped dolphin (S. coeruleoalba), common dolphin (Delphinus capensis), rough-toothed dolphin (Steno bredanensis), short-finned pilot whale (Globicephala macrorhynchus), killer whale (Orcinus orca), Risso's dolphin (Grampus griseus), humpback whale (Megaptera novaeangliae), Bryde's/Eden's whale (Balaenoptera brydei/edeni), sperm whale (Physeter macrocephalus) and an unidentified beaked whale (Mesoplodon sp.). All cetaceans were sighted within 22 km of the coast in relatively shallow waters. Sighting rate was low (0.69 cetacean sightings per 100 km). Sightings of calves and neonates indicate that Aruba may be a nursing or breeding area for some species. The presence of several species of cetaceans in Aruba's coastal waters year-round indicates that status and threat assessments are needed to protect them.

Sperm whale (Physeter macrocephalus) acoustic ecology at Ocean Station PAPA in the Gulf of Alaska – Part 2: Oceanographic drivers of interannual variability

2019 ◽  
Vol 150 ◽  
pp. 103044
Author(s):  
Nikoletta Diogou ◽  
Daniel M. Palacios ◽  
Jeffrey A. Nystuen ◽  
Evangelos Papathanassiou ◽  
Stelios Katsanevakis ◽  
...  
Keyword(s):  
Interannual Variability ◽  
Sperm Whale ◽  
Gulf Of Alaska ◽  
Physeter Macrocephalus ◽  
Acoustic Ecology ◽  
Ocean Station Papa

Detecting environmental regimes in fish stock-recruitment relationships by fuzzy logic

2001 ◽  
Vol 58 (11) ◽  
pp. 2139-2148 ◽  
Author(s):  
D G Chen
Keyword(s):  
Fuzzy Logic ◽  
Environmental Variable ◽  
Clupea Harengus ◽  
Fish Stock ◽  
Environmental Regimes ◽  
Fuzzy Logic Approach ◽  
Stock Recruitment ◽  
Logic Approach ◽  
Traditional Approaches ◽  
The Impact

A fuzzy logic approach is developed to model and test the impact of environmental regimes on fish stock–recruitment relationships. Traditional methods use environmental variables to classify stock–recruitment data into different membership percentiles followed by fitting the stock–recruitment models for each subset. In contrast, the fuzzy logic approach uses a continuous membership function to provide a rational basis for the classification. Thus, parameter estimation is based on a more logically consistent foundation without resorting to subjective partitions. This new approach is applied to herring stock from the west coast of Vancouver Island (Clupea harengus pallasi) using sea surface temperature as the environmental variable and to Pacific halibut stock (Hippoglossus stenolepis) using the Pacific Decadal Oscillation as the environmental variable. From these applications, the herring stock–recruitment relationships were found to vary significantly during different regimes, whereas this was not the case for halibut. However, in both instances, the fuzzy logic approach demonstrated that density-dependent effects differed between regimes. The fuzzy logic model consistently outperformed traditional approaches as measured by several diagnostic criteria. Because fuzzy logic models address uncertainty better than traditional approaches, they have the potential to improve our ability to understand factors influencing stock–recruitment relationships and thereby manage fisheries more effectively.

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