Crab Plan Team Report North Pacific Fishery Management

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C 1 a Crab Plan Team Report, Urban reviewed information on the short and long term handling mortality of discarded crab relevant to. crab stock assessment and development of fishery management measures with an emphasis on EBS snow. crab Estimates of bycatch biomass during the fishery are multiplied by the handling mortality rate and. that product is added to the retained catch biomass to estimate total fishery mortality Hence assumptions. about handling mortality will affect the time series of estimates of total fishery mortality used in stock. assessment models the determination of annual OFLs and annual total catch accounting. In the EBS snow crab fishery the discarded catch of snow crab is about 1 3 of the catch of retained crab. the discarded snow crab are mainly males smaller than the size preferred by processors 4 inches carapace. width The EBS snow crab assessment model has been using 0 5 as the handling mortality rate for snow. crab discarded during the directed fishery Urban noted that there is high uncertainty on this value. consensus of the CPT discussion during the presentation was that rather than being directly estimated. from data the 0 5 value was largely based on balancing the concerns that handling mortality could be. close to 100 versus an assumption closer to 0 based on an inferred low retained crab deadloss rate. Urban reviewed the sources of short term handling mortality for discards during crab fisheries which. include trauma at dumping and sorting of the catch on deck anoxia and temperature stress on deck. Temperature stress and freezing is a particular concern for the winter snow crab fishery which is often. conducted during sub freezing temperatures that are known from laboratory studies to induce mortality in. snow crab e g Shirley and Warrenchuck and to freeze eyestalks ongoing project On deck sorting and. discarding may induce short term mortality long term mortality and long term reductions in. reproductive potential Short term mortality can be directly studied and estimated estimation of long. term effects is more difficult Long term effects could include increased risk to predation decreased. ability to feed or mate and increased mortality during molting Laboratory studies have confirmed that. increased mortality of molting Tanner crab after exposure to sub freezing temperatures and freezing of. eye stalks could be reasonably assumed to have long term effects on survival and reproduction. The RAMP approach provides a means to estimate short term 2 weeks mortality due to discarding by. scoring a suite of reflex responses of crab captured during fisheries prior to their being discarded. Previous studies by Allan Stoner allow short term mortality rates to be predicted from the RAMP reflex. response scores With RAMP scores recorded from uninjured snow crab caught on 22 vessels during. 2009 10 season the predicted handling mortality of discards varied from 1 4 to 32 among vessels. overall RAMP predicted mortality of discards using the data from all vessels was 5 9 Additional. studies on commercial fishing vessels were conducted on one vessel during the 2010 11 snow crab season. and on four vessels during the 2011 12 season The RAMP predicted handling mortality from the 2010 11. study was 4 6 and from the 2011 12 study was 4 5, The predicted handling mortality was negatively correlated with back deck temperature on the vessel. during the time that RAMP scoring occurred such that temperature can be used to predict handling. mortality e g predicted mortality was approximately 35 at 14 C and 10 at temperatures 6 C. Directly obtaining back deck temperatures on all vessels throughout the season is not feasible Urban. therefore used the temperatures recorded at the St Paul airport as a proxy for on deck temperatures to. extend the results to all vessels fishing Most of the temperatures recorded at the St Paul airport during. the 2009 10 season were at levels associated with low RAMP predicted mortality Urban estimated the. average per season handling mortality rate during the 1990 91 2010 11 seasons to be 4 with the. highest estimate for any single season to be 8 during the early 1990s using the historical St Paul. airport temperatures to estimate the freezing related handling mortality Urban provided ADF G s. estimates of injury rates of snow crab captured during the fishery Those estimates of injury rates from. data collected by observers during the 1997 98 and 1998 99 seasons are approximately 10 it should be. C 1 a Crab Plan Team Report, noted that data on injury rates observed during the 2009 10 2011 12 seasons in conjunction with the. RAMP study were lower Urban suggested that the injury rates could be used to predict short term. mortality due to factors other than temperature, Urban acknowledged that a determination of the true handling mortality rate is difficult particularly when. considering the long term mortality Nonetheless he felt that evidence from the RAMP studies and the. observed injury rates suggest that the 0 5 currently assumed for handling mortality in the snow crab. assessment and for determining the OFL is too high Urban proposed three options for handling mortality. rates for use in the snow crab assessment status quo handling mortality rate 0 5 a conservative. approach a constant in the range of 0 15 0 20 based on adding the highest or average estimate of. RAMP predicted mortality and the highest observed injury rate or using the historic St Paul airport. temperatures and applying the temperature mortality relationship to obtain an annual handling mortality. Urban concluded his presentation with a summary of the attempts to develop a RAMP based method to. estimate handling mortality for red and golden king crab Those attempts were not successful and. suggested that the RAMP approach may have no useful application to king crab Red king crab mortality. showed no relationship with reflex response scores whereas experimenters had a difficult time inducing. the golden king crab subjects to die Urban noted that one observation from this study was that golden. king crab appear to be more hardy than red king crab As an example clipping the leg of a golden king. crab caused only 3 mortality significant mortality 80 required complete severing of the leg. The CPT discussed how to apply the findings presented for use in the snow crab stock assessment The. CPT was reminded that estimates used in the stock assessment should be unbiased and that conservation. concerns due to uncertainty should enter in the consideration of the ABC Much of the initial CPT. discussion focused on the uncertainty related to long term handling mortality and on the effects due to. discarding itself as opposed to the injuries suffered when brought on deck The CPT felt that the weight. of evidence is that 0 5 is too high but struggled with reconciling the results presented by Urban with the. uncertainty associated with other long term effects to survival growth and reproduction e g predation. displacement affects to hormone regulation additional stresses during molting etc Some voiced. concerns that given those uncertainties the CPT may be placing more weight on the results of recent. studies than is warranted With regard to some of the concerns it was noted that most of the discards are. males 3 inches carapace width which Urban noted may have low risk of predation relative to smaller. crab In addition although the long term effects will be much higher for crab that will molt data collected. on chela heights of males captured during the fishery suggest that most of the discarded males have. already completed their terminal molt, Discussion provided four options to consider for a total handling mortality rate for snow crab.
0 2 derived by summing the highest estimate due to freezing 0 08 with the highest estimate of. injury rates 0 12 i e one of the options that Urban presented. 0 25 derived as a balance between the extremes of 0 0 and 0 5 the argument for this was that it. was consistent with the approach to obtain the currently used 0 5 which was derived as a balance. between the two extremes of 0 0 and 1 0, 0 3 derived by taking the base of 20 handling mortality that is applied to king crab stocks. and adding the highest estimate of freezing related handling mortality 0 08 and rounding up to. the nearest 0 1, 0 3 derived by summing the highest estimate due to freezing 0 08 with the highest estimate of. injury rates 0 12 to capture the short term mortality and multiplying that sum by 1 5 to provide. an estimate that includes long term mortality Since there is no information on long term. C 1 a Crab Plan Team Report, mortality the CPT agreed that the best first order estimate of the long term mortality is 50 of. the short term mortality, The consensus of the CPT was that the best current estimate of handling mortality of snow crab was 0 3. based on the argument of the last bullet above The CPT requested that the next snow crab assessment. use 0 3 as handling mortality for all pot fisheries crab and fish in the base run and 0 5 as an alternative. scenario there was some discussion as to whether 0 3 or 0 5 should be the base but if 0 3 is chosen it. should be the base run so that the new handling mortality is included in the remaining alternative runs. The 0 5 run should be included so that the effects on OFL stock status etc can be evaluated. The CPT recommended that the 0 3 handling mortality not be applied to Tanner crab neither as bycatch. in the snow crab fishery or in the directed Tanner crab fishery i e the recommended handling mortality. for Tanner crab remains at 0 5 until sufficient data suggests otherwise Stoner s work suggests that Tanner. crab may suffer higher handling mortality than snow crab but no data were presented at this meeting for. Tanner crab similar to what were presented for snow crab The CPT recommended that a sensitivity. analysis on handling mortality be done in the Tanner crab assessment to provide impetus for research on. Tanner handling mortality during the snow crab fishery because Tanner bycatch mortality during snow. crab fishery has a large effect on the Tanner crab stock assessment OFL setting and available TAC. Discussion turned to the results that Urban presented on king crabs for which the RAMP approach. appears to be not useful Currently the Bristol Bay red king crab and the golden king crab assessments. assume that handling mortality is 0 2 Although on deck injury rates for king crab during the red and. golden king crab fisheries have been estimated using data collected by ADF G during the late 1990s no. new data was presented on king crab handling mortality at the meeting The CPT discussed the apparently. greater hardiness of golden king crab relative to red king crab and some members of the public. suggested that this observation could justify reducing the handling mortality used for golden king crab to. less than 0 2 The CPT was unable to recommend a change to the golden king crab handling mortality on. the basis of what was presented during the meeting and recommended that it stay at the status quo 0 2. until some data providing estimates of the handling mortality rate are presented It was noted that both the. golden king crab stocks Aleutian Islands and Pribilof Islands are currently managed as Tier 5 stocks for. which the assumed handling mortality rates have no impact on the retained catch portion of the OFL or of. the ABC handling mortality would become an important consideration if the golden king crab stocks. become managed under Tier 4, The CPT emphasizes that handling mortality remains a priority research objective for king crab species.
and Tanner crab,3 Advanced sampling, Bob Foy and Martin Dorn provided an overview of the advanced sampling technology AST program at. NMFS and the work of the AST coordination committee at the AFSC The AFSC effort is to better align. the annual process for funding advanced technology with the assessment needs of FMP species The CPT. was asked to suggest specific technologies that might be important to crab assessment Tagging methods. and assessment of crab in untrawlable areas were briefly discussed Crab stock assessment authors were. asked to fill out a survey also being sent to groundfish assessment authors to rank the availability of. information for stock assessment and to identify the most important data gaps in the assessments. 4 Generic crab model overview, The CPT received a presentation from Andr Punt on progress in developing a generalized crab. assessment model This work will allow more crab stock assessments to be conducted and standardized. C 1 a Crab Plan Team Report, ensuring model code works as intended and facilitating their review The project will be informed by. initial work by Mark Maunder to develop a modeling framework for crab that was supported by the crab. industry Dr Athol Whitten a Post Doc at the University of Washington has primary responsibility for. model development working under supervision of Andr There are two nested projects a to develop a. set of AD model builder ADMB routines for use in stock assessment models Common Stock. Assessment Routines Cstar and b to develop a generic crab model Generalized Modeling for. Alaskan Crab Stocks Gmacs that employs these routines Gmacs will be written in ADMB but the. analyst will interact with the software by using control files to select among modeling options and by. using data files to input assessment data A script in the R statistical language will be developed to. C 1 a Crab Plan Team Report 1 Crab Plan Team Report The North Pacific Fishery Management Council s Crab Plan Team CPT met April 30 May 3 2013 at the Clarion Suites in Anchorage AK The meeting was also broadcast on WebEx Documents and presentations for the meeting are posted at tinyurl ak crab Crab Plan Team members present

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