Atlantic States Marine Fisheries Commission

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Atlantic States Marine Fisheries Commission1050 N. Highland Street Suite 200A-N Arlington, VA 22201703.842.0740 703.842.0741 (fax) www.asmfc.orgMEMORANDUMOctober 5, 2016To:Atlantic Striped Bass Management BoardFrom:Atlantic Striped Bass Technical CommitteeRE:2016 Atlantic Striped Bass Stock Assessment UpdateThe 2016 Atlantic Striped Bass Stock Assessment Update utilizes catch and index data from 19822015.In 2015, the Atlantic striped bass stock was not overfished or experiencing overfishing based on thepoint estimates of fully-recruited fishing mortality (F) and female spawning stock biomass (SSB)relative to the reference points defined in Atlantic Striped Bass Fishery Management Plan. SSB wasestimated at 58,853 metric tons (129 million pounds) which is above the SSB threshold of 57,626metric tons, but below the SSB target of 72,032 metric tons. Total F was estimated at 0.16 which isbelow the F threshold of 0.22 and below the F target of 0.18.Commercial removals, i.e., landings plus dead discards, in 2015 were estimated at 917,264 fish.Recreational removals, i.e., angler harvest plus dead releases, in 2015 were estimated at 2,100,094fish.Total abundance (age 1 ) increased to 195 million fish by 2012 due primarily to the abundant 2011year-class from the Chesapeake Bay. Total abundance dropped in 2013 as the small 2012 year-classrecruited to the population. Abundance increased slightly in 2014 to 127 million fish, and in 2015total abundance was estimated at 180 million fish. Abundance of age 8 fish has declined since 2012and is expected to drop slightly in 2016.According to the projections model, if a constant catch of 3,017,358 fish, i.e., 2015 total removals,was maintained during 2016-2018, the probability of SSB falling below the threshold is 0.39 in 2016and declines to 0.20 by 2018. The fully-recruited F is expected to decrease to 0.14 by 2018. Theprobability of F being above the F target is 0.08 by 2018 and there is little chance (near zero) that Fwould exceed the F threshold.Enclosed: 2016 Atlantic Striped Bass Stock Assessment UpdateCC:Atlantic Striped Bass Technical CommitteeAtlantic Striped Bass Stock Assessment SubcommitteeAtlantic Striped Bass Advisory PanelM16-088Vision: Sustainably Managing Atlantic Coastal Fisheries

Atlantic States Marine Fisheries CommissionAtlantic Striped Bass Stock Assessment Update2016Prepared by:Atlantic Striped Bass Technical CommitteeSustainably Managing Atlantic Coastal Fisheries1

Update of the Striped Bass Stock Assessment Using Data Through 2015This document summarizes the striped bass assessment that uses catch and index data from 19822015.Commercial Data SourcesStrict quota monitoring is conducted by states through various state and federal dealer andfishermen reporting systems. Landings are compiled annually from those sources by state biologists.Commercial harvest in some states is recorded in pounds and is converted to number of fish usingconversion methods. Biological data (e.g., length, weight, etc.) and age structures (scales) fromcommercial harvest are collected from a variety of gear types through state-specific port samplingprograms. Harvest numbers are apportioned to age classes using length frequencies and age-lengthkeys derived from biological sampling.Commercial Landings (Weight)Historically, annual commercial harvest of striped bass peaked at almost 6,804 mt (15 millionpounds) in 1973. Landings declined precipitously to 63 mt (140,000 pounds) by 1986. Commerciallandings increased from 313 mt (690,039 pounds) in 1990 to 3,332 mt (7.3 million pounds) in 2004following liberalization of fishery regulations. Since 2005, landings have fluctuated about an averageof 3,162 mt (6.97 million pounds); however, landings have declined slightly in recent years (20112014) and further declined in 2015 as a result of quota reductions (Figure 1).Commercial Landings (Numbers)Commercial harvest of striped bass was over one million fish from 1997 through 2000 and near onemillion fish through 2006 (Table 1). Since 2007, numbers of fish landed have declined (Table 1). In2015, only 617,698 fish were harvested and the Chesapeake Bay jurisdictions (Maryland, Virginia,and the Potomac River Fisheries Commission (PRFC)) accounted for 82% of the numbers of stripedbass harvested (Table 1).Commercial Landings Age CompositionThe age structure of commercial harvest varies by state due to size regulations and season of thefisheries. The coast-wide time series of commercial-harvest age composition is provided in Table 2.In 2015, the commercial harvest was comprised primarily of ages 3-10 striped bass (Table 2). Harvestin Chesapeake Bay fisheries (Maryland, Virginia, and the PRFC) was comprised mostly of ages 3-8(Table 3).Commercial DiscardsDiscard estimates for fisheries in Chesapeake Bay, the Ocean and Delaware Bay are based on theratio of tags reported from discarded fish in the commercial fishery to tags reported from discarded2

fish in the recreational fishery, scaled by total recreational discards. Total commercial discards in2015 were estimated to be 1.4 million fish.Total discards are allocated to fishing gears based on the relative number of tags recovered by eachgear. Discards by fishing gear were multiplied by gear specific release mortalities and summed toestimate total number of dead discards in a given year. The estimates of dead discards are 299,566fish for 2015 (Table 4).Age Composition of Commercial Dead DiscardsCommercial discard proportions at age were obtained by applying age distributions from fisherydependent sampling or independent surveys that used comparable gear types. Gear specificproportions at age were applied to discard estimates by gear and the expanded estimates weresummed across all gears. Most commercial discards since 2004 were fish of ages 3-7 (Table 4).Total Removals by Commercial FisheriesTotal commercial striped bass removals (harvest plus dead discards) were 917,264 fish in 2015.Except for 2014, harvest has generally exceeded dead discards since the mid-1990s (Figure 2).Commercial losses in 2015 were dominated by the 2011 year-class (age 4).Recreational Data SourcesInformation on harvest and release numbers, harvest weights, and sizes of harvested bass from1982-2003 come from the National Marine Fisheries Service’s Marine Recreational FisheriesStatistics Survey (MRFSS/MRIP). The MRFSS/MRIP data collection consisted of a stratified interceptsurvey of anglers at fishing access sites that obtained numbers of fish harvested and released perangler trip, and a telephone survey that derived numbers of angler trips. Estimates of harvest andrelease numbers are derived on a bi-monthly basis.In response to a peer review of the MRFSS program (National Resource Council 2006), NMFSestablished the Marine Recreational Information Program (MRIP) to improve recreational datacollection and estimation methodologies. MRIP estimates are now calculated assuming intercepts ata site represent a cluster of samples, and sample sites are weighted by their probability of selection,which is a function of fishing pressure recommended by state advisors. The MRFSS estimationprocedure assumed that each intercept was an independent observation and that all sites wereequally likely to have been sampled. Re-estimation of catch and harvest from 2004-2010 using thenew methodology occurred in 2011 and is the standard used presently. However, the additional sitemetadata needed to replicate the MRIP estimation method are not currently available prior to 2004;therefore, estimates of catch for 1982–2003 are based on the MRFSS methodology.Anecdotal evidence had suggested that North Carolina, Virginia, and possibly other states hadsizeable wave-1 fisheries beginning in 1996 (wave-1 sampling that began in 2004 in North Carolinawaters and large wave-1 tag return data for North Carolina and Virginia supported this contention).3

However, MRFSS/MRIP did not sample in January and February (wave-1) prior to 2004; therefore,there was little information for the winter fishery (Jan, Feb) that had developed off of North Carolinaand Virginia. Harvest in wave 1 for these fisheries was estimated back to 1996 using observedrelationships between landings and tag returns. For North Carolina, the ratio of estimated landingsto tag returns in wave-1 of 2004 and annual tag returns in wave-1 were used to estimate annuallandings from tag returns in January and February of 1996-2003. For Virginia waters, the 1996-2004mean ratio of landings and tag returns in wave-6 and annual tag returns in wave-1 were used toestimate landings from tag returns in January and February of 1996-2004. For 2005-2012,MRFSS/MRIP wave-1 estimates of harvest for the winter fishery in Virginia waters were stillunavailable; therefore, they were estimated. The approach used to estimate wave-1 harvest in prioryears was abandoned because correlation between wave 6 harvest and tag returns off Virginiaweakened significantly. In 2012, the regression method of Nelson (NEFSC, 2013) was updated toinclude the new MRIP NC wave 1 estimates of harvest and 2012 MRIP and tag data, and the wave 1estimates from 2005-2012 were re-estimated. For 2015, the 2005-2012 regression was used toestimate Virginia wave-1 harvest. Dead releases for the winter recreational fishery in North Carolinaand Virginia were not estimated.Most states use the length frequency distributions of harvested striped bass measured by theMRFSS. The MRFSS measurements are converted from fork length (inches) to total length (inches)using conversion equations. Proportions-at-length are calculated and multiplied by the MRFSSharvest numbers to obtain total number harvested-at-length. Data on sizes of released striped basscome mostly from state-specific sampling or volunteer angling programs. Proportions-at-length arecalculated and multiplied by the number of MRFSS/MRIP dead releases to obtain the total numberof dead releases-at-length. For those programs that do not collect data on released fish, the lengthsof tagged fish released by anglers participating in the American Littoral Society’s striped bass taggingprogram or from state-sponsored tagging programs are used. Details on calculations are given in the2013 SARC document (NEFSC, 2013).Many states collect scale samples during state sampling programs designed to collect information onharvest and released striped bass from the recreational fishery. Age-length keys are usuallyconstructed and applied to harvest and dead release numbers-at-length. When sampling of therecreational fishery does not occur, age-length keys are constructed by using data on age-lengthfrom commercial sampling, fisheries-independent sampling or striped bass tagging programs. Forthose states that do not collect scale samples, age-length keys are usually borrowed fromneighboring states.Age composition of the January/February recreational fishery in North Carolina and Virginia wasestimated from length-frequency data collected by MRFSS/MRIP and appropriate state age-lengthkeys. Length-frequencies for the North Carolina winter harvest of 2004 came from data in wave-6 of2003 and wave-1 of 2004. Length-frequencies for the winter harvests of 1996-2003 came fromwave-6 of year t-1. Lengths were converted to age for North Carolina with a combined age-lengthkey from New York and North Carolina. Length-frequencies for the Virginia winter harvest in 19962012 came from MRFSS/MRIP data in wave-6 of year t-1. The Virginia lengths were converted to agewith a Virginia age-length key in 2013, and used the MD coast age distribution was used to4

apportion wave-1 harvest to age classes in 2014 and 2015 (there was no coastal age data providedby VA).Recreational Total LandingsFigure 1 traces the impressive growth of the Atlantic coast-wide recreational fisheries from 1982through 2015. Harvest increased from 1,010 mt (2.2 million pounds) in 1990 to 14,082 mt (31 millionpounds) in 2006 (Figure 1). Following the peak in 2006, harvest declined through 2012 to 8,740 mt(19 million pounds), increased in 2013 and 2014, and declined in 2015 due to changes in bag and sizelimits (Figure 1).Recreational Landings in NumbersRecreational harvest of striped bass was greater than 1.4 million fish from 1997 through 2006, andmore than 2.4 million striped bass during 2003-2006 (Table 5). Harvest was generally highest inVirginia, Maryland, New Jersey, and Massachusetts (Table 5). Coast-wide harvest of striped bassdeclined to 1.5 million fish in 2012, increased to an average of 1.97 million fish in 2013-2014, anddeclined to 1.34 million fish (Table 5).Age Composition of Recreational LandingsTime series of harvest numbers-at-age are given in Table 6. Coast-wide recreational harvest wasdominated by the 2011 (age 4) and 2010 (age 5) year-classes in 2015 (Table 7). Ages 4-10 comprisedabout 79% of the coast-wide harvest in 2015, and ages 8 comprised about 41% (Table 6).Recreational harvest from the ocean states (includes Delaware Bay) was comprised mostly (70%) ofages 5-10, while harvest in Chesapeake Bay (MD and VA) was dominated by ages 4-8 (70%) (Table 7).Recreational Dead ReleasesThe number of striped bass that are caught and released (B2) is estimated by MRFSS/MRIP (Table 8).The releases have accounted for 85 to 90% of the annual catch in most years (Figure 2). The numberof releases that die due to the capture and release process is estimated by multiplying the totalrelease numbers (B2) by an estimate of hooking mortality. The overall 9% hooking mortality rateestimated by Diodati and Richards (1996) was used. Estimates of the number of dead releases arepresented in Table 9. The numbers of fish released dead increased from 132 thousand fish in 1990 to1.4 million fish in 1997. Releases remained around 1.2 million through 2003, but increased to theseries maximum of 2.1 million fish in 2006. Releases declined substantially from 2006 through 2012(Table 9). The number of dead releases increased to 768,599 fish in 2013