Assessment of River Herring and Striped Bass in the Connecticut River: Abundance, Population Structure, and Predator/Prey Interactions

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1 University of Connecticut EEB Articles Deprtment of Ecology nd Evolutionry Biology 2009 Assessment of River Herring nd Striped Bss in the Connecticut River: Aundnce, Popultion Structure, nd Predtor/Prey Interctions Justin P. Dvis University of Connecticut - Storrs, justin.dvis@ct.gov Eric T. Schultz University of Connecticut - Storrs Json Vokoun University of Connecticut - Storrs Follow this nd dditionl works t: Prt of the Aquculture nd Fisheries Commons, Biology Commons, Popultion Biology Commons, nd the Terrestril nd Aqutic Ecology Commons Recommended Cittion Dvis, Justin P.; Schultz, Eric T.; nd Vokoun, Json, "Assessment of River Herring nd Striped Bss in the Connecticut River: Aundnce, Popultion Structure, nd Predtor/Prey Interctions" (2009). EEB Articles

2 Assessment of River Herring nd Striped Bss in the Connecticut River: Aundnce, Popultion Structure, nd Predtor/Prey Interctions Drft Finl Report Sumitted to the Connecticut Deprtment of Environmentl Protection By Justin Dvis, PhD Cndidte 1 Eric Schultz, Principl Investigtor 1 Json Vokoun, Co-Principl Investigtor 2 1 Deprtment of Ecology nd Evolutionry Biology 2 Deprtment of Nturl Resources nd Environment University of Connecticut Storrs, Connecticut Mrch 30, 2009

3 Dvis et l., Assessment of River Herring nd Striped Bss Finl Report i Executive Summry Purposes of the Project Popultions of ndromous lewife Alos pseudohrengus nd lueck herring Alos estivlis, collectively referred to s river herring, hve declined in the Connecticut River. The numer of lueck herring pssing Holyoke Dm, the most downstrem dm on the minstem Connecticut River, hs declined from 630,000 in 1985 to recent low of 21 in An hypothesis for why river herring hve declined in the Connecticut River is tht predtion pressures hve incresed, prticulrly ssocited with recent increses in undnce of striped ss Morone sxtilis. This study ws designed to test this hypothesis. It will serve s strting point for the formultion of river herring conservtion plns, the collection of long-term dtsets, nd the development of future reserch directions. Ojectives Assess undnce, temporl/sptil distriution, nd popultion structure of river herring in the Connecticut River elow Holyoke Dm Assess undnce, temporl/sptil distriution, nd size structure of striped ss in the Connecticut River elow Holyoke Dm Chrcterize predtor/prey interctions etween striped ss nd river herring in the Connecticut River elow Holyoke Dm Methods The river stretch from Wethersfield, CT to Holyoke, MA ws selected s the study region. This region ws selected ecuse its long-river length, depth nd width were conducive to smpling, nd ecuse prior informtion indicted tht striped ss nd river herring congregte there. The region ws smpled in Smpling occurred during mid-april to June, which is the spring migrtory seson for river herring nd striped ss in the Connecticut River (Svoy nd Crecco 2004). Experimentl smpling in April-erly My of 2005 focused on identifiction of effective smpling techniques for river herring nd striped ss, s well s selection of stndrdized smple sites within the study region. Initil smpling in 2005 employed severl gers, including nchored nd drifting gill nets, ech seines, controlled ngling, nd night-time ot electrofishing. Bot electrofishing ws most efficient, nd ws used in conjunction with nchored gill-nets nd controlled ngling for the reminder of Bot electrofishing ws used exclusively in Five smple sites were selected in 2005: Wethersfield, the lower Frmington River, Windsor Locks, Enfield, nd Holyoke, MA. These sites were selected sed on criteri including reltive spcing long the study stretch, ctch rtes of trget species, nvigtion sfety, nd ese of ccess. The five stndrd smple sites ccounted for the mjority of 2005 smpling nd were used exclusively in Smpling in 2008 ws restricted to Windsor Locks to support striped ss mrk-recpture efforts (see elow).

4 Dvis et l., Assessment of River Herring nd Striped Bss Finl Report ii Smple sites were visited once per clendr week during the 2005, 2006 nd 2007 smpling sesons, river conditions nd equipment permitting. Fixed electrofishing trnsects were smpled in systemtic fshion on ech smple night. All river herring cptured in were enumerted nd mesured for totl length (TL, in mm). Up to five herring per 5-mm size clss were euthnized on ech smple night. Fish in these su-smples were returned to the l for sex, species, ge, nd spwning history determintion. No river herring were collected in 2008 s smpling focused on striped ss mrk-recpture efforts (see elow). All striped ss cptured in were enumerted nd mesured. In 2005 nd 2006, ll striped ss were weighed (kg), nd diet smples were collected from ll striped ss 300 mm TL vi gstric lvge. In 2007, striped ss were weighed nd lvged on suset of smple nights (see elow). In , ll striped ss 300 mm TL were tgged (see elow). No striped ss were weighed or lvged in The mjority of striped ss (> 99%) collected were relesed. A striped ss mrk-recpture study ws initited in 2006 to provide estimtes of popultion size in the study region during the spring migrtory seson. All striped ss 300 mm TL were tgged with uniquely-coded internl nchor FLOY tgs. Tgs fetured phone numer tht nglers could cll to report recpture of tgged fish. Tgging ws conducted during norml smpling opertions in In 2007, dditionl funding ws otined to field n independent smpling crew devoted solely to the mrk-recpture study. The mrk-recpture crew smpled Windsor Locks exclusively, nd did not lvge or weigh striped ss (enumertion, mesuring, nd tgging only). Field smpling in 2008 ws restricted to mrk-recpture efforts (enumertion, mesuring, nd tgging of striped ss in Windsor Locks). Sptiotemporl ptterns of striped ss nd river herring undnce were ssessed using electrofishing ctch rtes in 2005, 2006 nd Distriutions of the two species were ssessed for degree of overlp. Otoliths nd scles were removed from ll su-smpled herring for ge nd spwning history nlysis. An ge-length key pproch (Devries nd Frie 1996) ws used to determine popultion structure with respect to ge nd spwning history. Contemporry dt were compred to historic dt (Loesch 1987) to ssess decdl shifts in popultion structure. Striped ss diet smples were sorted y prey ctegory. Prey items were enumerted, weighed (g), nd mesured for length (TL, mm) when possile. Diet composition ws summrized s percent frequency of occurrence, percent composition y mss, nd percent composition y numer (Bowen 1996). A mel turnover model (Adms nd Breck 1990) ws used to estimte striped ss percpit consumption rtes for river herring nd Americn shd prey. Striped ss mrk-recpture dt were used to estimte popultion size using Schnel mrk-recpture model (Hyes et l. 2007). Estimtes of striped ss per-cpit consumption rtes nd popultion size were used to estimte popultion-level consumption of river herring nd Americn shd prey (Tor et l. 2007).

5 Dvis et l., Assessment of River Herring nd Striped Bss Finl Report iii Key Findings Over 100 smpling trips were completed in four field sesons. Smpling egn in April, ut ws spordic until erly My due to river flooding. Field opertions were generlly terminted in mid-lte June due to persistently low ctch rtes of trget species nd low river flows. Over 3,000 river herring were collected in Almost ll river herring collected were lueck herring; lewives comprised < 3% of su-smpled fish. Over 2,000 striped ss were collected in Approximtely 700 of these fish were sujected to gstric lvge, nd pproximtely 1,400 were tgged. Blueck herring were most undnt in the downstrem end of the study region nd lowest t upstrem sites. Herring ctch rtes vried more thn n order of mgnitude etween the upstrem nd downstrem ends of the region. Blueck herring undnce vried over the smple seson. Herring were generlly most undnt in erly-mid My, nd severl susequent wves of undnce were often oserved. Blueck herring verged mm TL. Size structure differed mong yers. Smple site did not hve significnt effect on herring size. Herring size decresed s the seson progressed. Otolith nd scles did not yield concordnt estimtes of lueck herring ge, despite similr levels of etween-reder greement. Otoliths were selected s the preferred structure for ge estimtion. Scles were used to estimte spwning history s otoliths do not contin informtion on previous spwning ctivity. The lueck herring spwning run ws composed primrily of ge 3 6 fish. The 2005 run contined reltively lrge numer of fish ge 5 nd older, nd pproximtely 30% of fish were repet spwners. The 2006 nd 2007 runs were dominted y strong 2003 yer clss, nd 15% of fish were repet-spwners. Comprisons of contemporry lueck herring popultion structure to historicl dt from Connecticut (Loesch 1987) indicte significnt decdl shifts. Blueck herring in 1960 s spwning runs were 6 16% lrger thn recent fish. The lueck herring run in 1966 ws dominted y fish ge 5 nd older, fish younger thn ge 4 were reltively rre, nd pproximtely 82% of fish were repet-spwners. A wide size rnge of striped ss ws cptured (min = 156 mm, mx = 1224 mm, medin = 430 mm). Striped ss were clssified y size into two groups, divided t size close to the medin of the distriution: Smll ( 500 mm TL) nd Lrge (> 500 mm TL). Sesonlly-verged undnce of Smll striped ss ws highest in Windsor Locks in ll yers. Sesonlly-verged undnce of Lrge striped ss incresed upriver, eing lowest in Wethersfield nd gretest in Holyoke. Vrition in long-river undnce of Lrge striped ss pproched or exceeded n order of mgnitude in ll yers. River-wide undnce of Smll striped ss vried temporlly in some yers ut did not disply consistent pttern. There ws no temporl vrition in river-wide undnce of Lrge striped ss in ny yer. Averge striped ss size consistently incresed long-river in ech yer, such tht striped ss were lrgest in Holyoke.

6 Dvis et l., Assessment of River Herring nd Striped Bss Finl Report iv Striped ss size structure differed mong yers. Averge size grdully declined cross the time period of this study. Lrge striped ss nd river herring displyed similr sesonl ptterns of undnce. Both species were most undnt in the study region in My nd erly June. Lrge striped ss nd river herring showed inverse ptterns of long-river distriution. Recpture rtes of tgged striped ss within the study region during the smpling seson were 2.7% nd 3.3% in 2007 nd 2008, respectively. Low recpture rtes nd lck of multiple recptures of the sme tgged fish precluded use of open popultion mrk-recpture models. A closed popultion model (Schnel) ws used to estimte striped ss popultion size in the river stretch from Hrtford, CT to the MA/CT order in My Popultion size ws estimted s 65,744 striped ss 300 mm TL (95% confidence intervl = 2, ,573). Diet smples were otined from 389 striped ss in Smller striped ss consumed vriety of fish nd inverterte prey. Lrger striped ss diets were more specilized nd contined mostly fish. River herring were prominent item in diets of mm TL striped ss. 74 striped ss diet smples contined river herring. Americn shd were the most prevlent diet item in 900 mm TL striped ss. 45 striped ss diet smples contined shd. A smll portion of the striped ss popultion (< 4%) feeds on Americn shd. Striped ss cpture of herring differed mong sites. Striped ss cpture success ws concordnt with the long-river distriution of Lrge striped ss ut not with the undnce of herring. Striped ss 400 mm TL consumed 0 2% ody mss dy -1 of river herring nd Americn shd. Striped ss 1000 mm TL consumed 3 7 % ody mss dy -1 of shd. Dily rtion estimtes were multiplied y the men mss of striped ss within ech size clss to estimte dily prey iomss consumption. Consumption of herring ws g dy -1, nd consumption of shd ws g dy -1. We estimte tht striped ss consumed over 200,000 herring (95% CI = 8, ,351) nd lmost 100,000 Americn shd (95% CI = 3, ,688) etween Hrtford, CT nd the MA/CT order in My Conclusions Blueck herring popultion structure hs chnged over recent decdes. Contemporry runs feture younger, smller fish tht re less likely to complete multiple spwning runs over their lifetime. These findings re consistent with our previous studies of river herring popultions in Connecticut (Dvis nd Schultz in press). The Connecticut River lueck herring popultion is more vulnerle to stressors s result of chnges in demogrphy nd life history. Decreses in iteroprity will result in lrger vritions in dult popultion size ecuse yers of poor juvenile survivl nd poor susequent recruitment will e followed y yers of depleted spwning migrtions. Younger, smller spwners produce fewer eggs nd possily lower-qulity lrve, reducing the reproductive potentil of the popultion.

7 Dvis et l., Assessment of River Herring nd Striped Bss Finl Report v The chnges in the Connecticut River lueck herring popultion indicte tht mortlity hs incresed mong older, lrger individuls, cused y fctors such s predtion or fisheries. Striped ss predtion in the Connecticut River is significnt source of mortlity for dult lueck herring. River herring represent significnt portion of striped ss diets in the Connecticut River during My June, nd striped ss congregte in loctions where they re successful in cpturing herring. The estimted sesonl consumption of river herring is sustntil; it fr exceeds the numer of herring tht re pssed t the Holyoke fish lift, nd is comprle to the numer tht pssed in yers efore shrp decline in the erly 1990 s. Modeling currently underwy will llow us to etter interpret the significnce of our findings with respect to lueck herring popultion dynmics. Such models cn e used to hindcst the impct of striped ss predtion on river herring run size in recent decdes, nd exmine potentil impcts of chnges in striped ss mngement. Future studies could significntly improve our understnding of the complex nd interrelted dynmics of river herring nd striped ss. These studies should focus on providing more roust estimtes of locl striped ss popultion size nd consumption rtes, s well s greter understnding of movements nd spwning ehvior of oth species within the Connecticut River. Recommendtions Continue ongoing popultion modeling efforts designed to hindcst the contriution of striped ss predtion to river herring declines in the Connecticut River in recent decdes. Assess the potentil for striped ss mngement chnges to llevite predtory pressure on lueck herring popultions. Develop vlidted ging protocols for lueck herring in the Connecticut River. These efforts will require cquisition of scles nd otoliths from known-ge fish, nd my incorporte totl evidence pproch tht relies on ge estimtes from oth structures. Conduct diet studies of costl striped ss popultions during My-June to ssess differences in cpture success nd consumption of river herring prey. Use either ioenergetics or gstric evcution models to provide more precise estimtes of striped ss consumption. Bioenergetics models will require detiled dt on striped ss growth during Connecticut River residence, s well s informtion on ctivity rtes. Gstric evcution models will require lortory experiments to mesure the thermldependency of gstric evcution rte for lrge striped ss feeding on lrge piscine prey. Conduct ichthyoplnkton studies designed to ssess long-river trends in river herring lrvl densities. Such studies will test the hypothesis tht striped ss predtion effects the long-river distriution of river herring spwning ctivity. If high undnce of lrge striped ss in the upper river trunctes river herring spwning migrtions, the Holyoke time series my over-estimte declines in nnul run size. In ddition, ichthyoplnkton surveys my lso confirm striped ss spwning ctivity in the Connecticut River. Conduct studies of juvenile lueck herring growth nd survivl in different portions of the Connecticut River. These studies will provide insight into the potentil enefits river herring ccrue y risking striped ss predtion to rech upriver spwning grounds nd the reltive importnce of spwning hitt ove Holyoke Dm.

8 Dvis et l., Assessment of River Herring nd Striped Bss Finl Report vi Consider estlishing long-term monitoring progrm to estlish time series of river herring nd striped ss undnce in the Connecticut River. Progrms such s these hve een estlished in other res (e.g. Hudson River, Chespeke By) nd hve provided gret enefits to fishery mngers. The smpling protocol used for our study could serve s templte for such long-term monitoring progrm. Develop more roust estimtes of striped ss popultion size in the Connecticut River. These studies should seek to employ open popultion models, nd will require more extensive tgging nd recpture efforts. Coordinted creel surveys will e required if nglers re relied on s the primry mens of tg recpture. Telemetry studies my lso provide etter insight into reltive rtes of movement into nd out of the study re. Assess the predtory impct of striped ss on juvenile losines in the Connecticut River during the lte summer fll. Lrge numers of smll striped ss re present in the Connecticut River yer-round, nd my consume considerle numer of juvenile river herring. Studies ssessing this predtor-prey interction should focus on the southern portion of the Connecticut River, nd my need to employ different gers thn our study.

9 Dvis et l., Assessment of River Herring nd Striped Bss Finl Report vii Tle of Contents Executive Summry Purposes of the Project... i Ojectives... i Methods... i Key Findings...iii Conclusions...iv Recommendtions... v Project Report Rtionle... 1 Species Bckground... 2 Ojectives... 3 Summry of Field Smpling Opertions Ojective 1: Assess Aundnce, Temporl/Sptil Distriution, nd Popultion Structure of River Herring... 6 Distriution nd undnce... 6 Size nd ge structure... 7 Ojective 2: Assess Aundnce, Temporl/Sptil Distriution, nd Size Structure of Striped Bss... 9 Distriution nd undnce... 9 Size structure Tg-recpture study Assocition of striped ss nd river herring in time nd spce Ojective 3: Chrcterize Predtor/Prey Interctions etween Striped Bss nd River Herring Striped ss diet Sptil vriility in striped ss cpture of lueck herring Per-cpit striped ss consumption rte Estimting popultion-level consumption rte of lueck herring nd shd Generl Conclusions nd Recommendtions References Tles Figures... 58

10 Dvis et l., Assessment of River Herring nd Striped Bss Finl Report 1 Project Report: Assessment of River Herring nd Striped Bss in the Connecticut River: Aundnce, Popultion Structure, nd Predtor/Prey Interctions Rtionle Popultions of ndromous lewife Alos pseudohrengus nd lueck herring Alos estivlis, collectively referred to s river herring, hve declined in the Connecticut River. The numer of lueck herring pssing Holyoke Dm, the most downstrem dm on the minstem Connecticut River, hs declined from 630,000 in 1985 to recent low of 21 in 2006 (U.S. Fish nd Wildlife Service, migrtory fish count dt t A comprle time series is not ville for lewife in Connecticut; evidence for this species decline is provided in recent review of commercil lndings dt nd in oservtions y Connecticut Deprtment of Environmentl Protection (CDEP) personnel (Dvis nd Schultz in press). In response to these pprent crshes of locl popultions, the Connecticut Deprtment of Environmentl Protection encted n emergency closure of the river herring fishery in the Connecticut River in This emergency closure remins in plce. Similr closures were instituted in the neighoring sttes of Msschusetts nd Rhode Islnd in The closures pply to oth costl nd ocen-intercept fisheries, nd therefore constitute mortorium on directed fisheries for river herring in southern New Englnd. An hypothesis for why river herring hve declined in the Connecticut River is tht predtion pressures hve incresed, prticulrly ssocited with recent increses in undnce of striped ss Morone sxtilis (Svoy nd Crecco 2004). Adult striped ss re lrge, piscivorous fish tht re known to consume menhden, shd nd river herring (Wlter et l. 2003). Striped ss popultions in the Atlntic costl region hve risen to historiclly high levels over the lst two decdes (Richrds nd Rgo 1999). The increse in striped ss undnce hs resulted in predictle increse in predtory pressure exerted y striped ss throughout their rnge (Wlter et l. 2003). A temporl correspondence etween incresing striped ss popultions nd declining river herring popultion within the Connecticut River suggests cusl reltionship tht ers more detiled study (Svoy nd Crecco 2004). Unfortuntely, despite wide knowledge tht striped ss re sesonlly undnt in the River, virtully nothing is known of their sptiotemporl distriution, size structure, or prey use. Such dt re needed for full ssessment of the role these predtors my hve plyed in driving declines of river herring. Prior to this project there hs een no quntittive smpling for river herring in the lower Connecticut River side from the long-term dtset on lueck herring undnce t Holyoke Dm. Informtion on river herring undnce ws limited to necdotl reports y memers of the pulic nd qulittive oservtions y CDEP personnel. The sptil nd temporl chrcteristics of upstrem migrtion y river herring over the course of the spwning seson were poorly understood. There ws no informtion on the current size structure, ge structure, or growth chrcteristics of Connecticut River herring. Previous study of lewife spwning in CT costl strem with hedpond (Bride Brook) suggested tht ge structure nd life history hve shifted drmticlly in the lst 40 yers; fish on the spwning run re now younger, nd re more likely to e first-time spwners or virgins (Dvis nd Schultz in press). This shift is symptomtic of high exploittion or predtion pressure nd increses the vulnerility of the popultion to further stressors.

11 Dvis et l., Assessment of River Herring nd Striped Bss Finl Report 2 This study ws designed to test the hypothesis tht locl popultions of herring hve een suject to top-down control y striped ss. Severl predictions of this hypothesis were tested. One prediction is tht the popultions of presumptive predtor nd prey come into close contct. Both species re known to concentrte in the river during their sesonl migrtions; we smpled to determine if the sptil nd temporl ptterns of reltive herring nd striped ss undnce correspond. Another prediction is tht dult striped ss in the River re lrge enough to consume dult river herring. We quntified the size dependence of striped ss predtion on river herring. Size dependence is of prticulr interest ecuse fishery mngement tools such s size limits cn hve direct impct on the size structure of the predtor popultion (if hrvest or hooking mortlity is sustntil), nd therefore could hve n indirect effect on recovery prospects for prey species. A third prediction is tht the striped ss re cple of consuming n pprecile proportion of river herring. To ddress this prediction, we will model n estimted predtion rte using dt on popultion size, size structure nd consumption rtes. Informtion gthered y this study is necessry to more precisely chrcterize the decline of river herring popultions within the Connecticut River, nd will inform the dete over the mechnisms driving these declines. This study will serve s strting point for the formultion of river herring conservtion plns, the collection of long-term dtsets, nd the development of future reserch directions. Species Bckground Andromous lewife nd lueck herring hve lrgely symptric distriution long the Atlntic cost of North Americ, from the mritime provinces of Cnd to the southestern US (Mullen et l. 1986). The species re quite similr, nd re often referred to genericlly s river herring throughout their rnge. Adults inhit reltively shllow (<100m) wters long the continentl shelf (Neves 1981). The timing of return to freshwter spwning hitts in spring vries with species (Mullen et l. 1986) nd is cued y temperture (Kissil 1974; Loesch 1987): lewives generlly spwn erlier in the seson t colder wter tempertures thn lueck herring. Juvenile river herring complete period of freshwter residence efore migrting to esturine or mrine environments during the period of June Novemer (Loesch 1987). During periods of freshwter nd esturine residence, oth dult nd juvenile river herring provide forge for numerous qutic, terrestril, nd vin predtors (Loesch 1987). Post-spwn mortlity of dult river herring lso provides n importnt ddition to the nutrient udget of mny qutic systems (Durin et l. 1979). Striped ss re n economiclly-importnt recretionl species ntive to the Atlntic cost of North Americ, from the St. Lwrence to northern Florid, nd long the northern shore of the Gulf of Mexico (Collette nd Klein-McPhee 2002). Lndlocked popultions hve een estlished in southestern reservoirs, nd the species hs lso een introduced well outside its ntive rnge in the US (Fuller et l. 1999). The fish is highly prized for food nd sport. Commercil lndings of the species peked t lmost 15 million pounds in 1973 nd then declined y more thn 75% over the next decde (Atlntic Sttes Mrine Fisheries Commission 1999). Following imposition of strict limits on commercil nd recretionl fishers, the stock ws declred fully recovered y the Atlntic Sttes Mrine Fisheries Commission in 1995; lndings hve continued to clim since then. The migrtory ehvior of this fish is complex nd remins poorly understood. Some individuls overwinter in southern New Englnd, ut most pper to rrive in the region in the springtime fter migrting from the mid-atlntic cost.

12 Dvis et l., Assessment of River Herring nd Striped Bss Finl Report 3 Vernl migrtions into fresh wters my not represent spwning migrtions in ll loctions, nd spwning of striped ss in the Connecticut River hs not een confirmed. Ojectives Our gol ws to test the hypothesis tht recent increses in striped ss popultions re suppressing the undnce of river herring popultions. The specific ojectives of the proposed reserch were to: 1) Assess undnce, temporl/sptil distriution, nd popultion dynmics of river herring in portion of the Connecticut River etween Hrtford nd the Holyoke Dm (referred to henceforth s the study region ); 2) Assess undnce, temporl/sptil distriution, nd size structure of striped ss in the study region; 3) Chrcterize predtor/prey interctions etween striped ss nd river herring. Summry of Field Smpling Opertions Project field smpling egn in spring of The gols of the 2005 smpling seson were to ) identify stndrdized smpling pproch for ssessment of sptil nd temporl distriution of striped ss nd river herring in the study region during spring months (April June); ) identify smpling techniques effective for the cpture of these trget species; nd c) otin smple sizes of these trget species lrge enough to permit effective nlysis of popultion structure. The study region ws selected due to its reltive nrrowness, shllow depth, nd the need to constrin smpling ctivities to n re smll enough to permit comprehensive weekly smpling. The prototype smpling pln ws strtified rndom, with clendr weeks serving s strt (herefter referred to s periods ). Five smpling trips were plnned on rndomlyselected dys within ech period. On ech smpling trip rndomly selected site within the study region would e smpled. Potentil smple sites were selected priori sed on reltive loction within the study region nd fesiility of smpling during norml workdy (i.e. trvel time from ot lunches). Smpling egn on 16 April 2005 nd continued spordiclly throughout the rest of April nd erly My 2005 when river conditions llowed for sfe nvigtion. During this erly portion of the 2005 field seson (4/16/05 5/9/05), 8 smpling trips were conducted. Anchored gill nets served s the primry smpling ger. Two experimentl monofilment gill net configurtions tht hd proven successful for herring nd striped ss cpture in the Hudson River were used (Mrk Mttson, Normndeu Assocites, personl communiction): 300 long y 8 deep, 3 x 100 pnels of 4, 5 nd 6 r mesh (trgeting striped ss, herefter referred to s the striper net ); 150 long y 8 deep, 3 x 50 pnels of 1.75, 2.25, nd 2.75 r mesh (trgeting river herring, herefter referred to s the herring net ). Gill-nets were deployed for minute sets during dylight hours t rndom loctions within the smple site. Nets were set from shore t n ngle olique to river flow nd t the top of the wter column. We experimented with dditionl gers, including drifting gill-nets, controlled ngling, nd ech seining. Gill net drifts used the sme nets s the nchored gill-nets descried ove. A ech seine configurtion tht hd proven successful for herring nd striped ss cpture on the Hudson River ws used (K. Httl, NYDEC, personl communiction: 300 long y 12 deep, 2 stretch mesh). No herring were cptured during the erly weeks of the 2005 smpling seson, nd ctch of striped ss ws spordic. It ws often difficult to effectively deploy nchored gill-nets due to high river flows, nd nets quickly ecme hevily fouled. Bech seine sets nd gill-net drifts

13 Dvis et l., Assessment of River Herring nd Striped Bss Finl Report 4 were lso unproductive, lrgely owing to derth of loctions conducive to these pproches (multiple sngs on river ottom, lck of eches lrge enough to lnd ech seine). A decision ws mde on 10 My 2005 to dopt ot electrofishing s the primry smpling method, nd to move smpling opertions to night-time hours. A Coffelt electrofishing ot (owned y the University of Connecticut herefter referred to s the UConn ot ) equipped with single, Wisconsin ring style electrode ws used for ot electrofishing opertions. Five stndrd smple sites were selected (Tle 1, Fig. 1): Wethersfield (WF), the mouth of the Frmington River (FR), Windsor Locks (WL), Enfield (EF), nd Holyoke, MA (HK). Ech site ws smpled on rndomly-selected night within clendr week, river conditions permitting. Occsionl electrofishing ws conducted t loctions other thn the stndrd sites. Fixed electrofishing trnsects were defined within ech smple site. Trnsects were generlly locted in ner-shore, shllow hitt ( 6 ft. wter depth) nd rn prllel to the shoreline. Trnsects were set to length tht corresponded to pproximtely 650 seconds of shocking time. These trnsects were smpled vi ot electrofishing in identicl fshion during every smpling night. We used fixed, rther thn rndomized, trnsect loctions for severl resons. Fixing loctions enled us to seprte trnsects y hitt (e.g. cove mouths, triutry mouths, minstem, tilrce), nd to smple multiple hitts. Fixed loctions lso proly furnished us with greter smple size for nlysis of striped ss diet nd popultion size thn would hve een relized with completely rndomized design; trnsects were estlished in plces tht were known to hold fish. The consequence of this decision is tht undnce estimtes re ised to n unknown degree. Anchored gill-nets nd controlled ngling were lso used in concert with electrofishing, primrily s mens of incresing smple sizes for the purpose of popultion structure nlyses. Smpling egn pproximtely 2 hours efore drk. Anchored gill-nets were deployed in fixed loctions tht hd een identified y tril nd error s hving the pproprite depth nd current. Gill-nets were mrked with lighted uoys in order to void oting mishps. Once the nchored gill-nets hd een deployed, controlled ngling ws performed y trveling to the upstrem end of the smple site nd then drifting downstrem with the mient current. Artificil lures 7 22 cm in length were used during controlled ngling. After drk, controlled ngling ws discontinued nd fixed electrofishing trnsects were smpled. Anchored gill-nets were retrieved once electrofishing ws complete. Fish were collected with ll three smpling methods in Over five week-long periods, smpling ws conducted on 27 nights, nd 82 electrofishing trnsects were completed (Tle 2). Electrofishing effort ws distriuted firly equitly over the five periods (Tle 3). Electrofishing effort ws distriuted unevenly mong sites ecuse nonstndrd sites were visited on some nights, in ddition to or in lieu of smpling stndrd site in tht period (Tle 2, Tle 4). Byctch ws recorded for gill net sets: fifteen species were cptured (Tle 5). Gill net effort ws distriuted unevenly mong sites (Tle 6) ecuse of differences in visit numer nd lso ecuse suitle loctions for nchored gill-nets were not ville t ech site. The herring net ws more effective thn the striper net (Tle 7, Tle 8). The herring net cptured primrily striped ss (Tle 7, Tle 9). Neither gill net configurtion cptured river herring. The striper net ws discontinued on 18 My 2005, nd the two herring nets were joined together to crete 300 long, 8 deep net consisting of 6 lternting pnels. Controlled ngling effort ws distriuted unevenly mong sites ecuse of differences in visit numer, nd ctch per unit effort lso vried mong sites (Tle 10). Smpling ws discontinued on 15 June 2005 in response to consistently low ctch rtes of trget species.

14 Dvis et l., Assessment of River Herring nd Striped Bss Finl Report 5 In susequent yers of field smpling ( ) we used modified version of the method used in the ltter prt of the 2005 field seson. We discontinued use of nchored gillnets nd controlled ngling, ecuse of low ctch rtes. Electrofishing efficiency improved vi the use of different electrofishing ot, Smith-Root Model SR-18 electrofishing ot (herefter referred to s the Smith-Root ot ) loned to us under contrctul greement with the USFWS CT River Coordintor s Office in Sunderlnd, MA. The Smith-Root ot (Fig. 2) ws equipped with two spider electrode rrys tht were more conducive to smpling in the lotic environment of the Connecticut River. The five stndrd smple sites identified in 2005 (Fig. 1) were used exclusively in susequent yers (i.e. there ws no experimentl smpling in other res) nd the timing of site visits ws systemtic within period. Ech site ws smpled on the sme dy within ech clendr week, such tht the intervl etween smpling events t site ws fixed t seven dys. The first smpling trip of 2006 took plce on 27 April. Thirty smpling trips were completed efore the finl trip on 30 June (Tle 11). All five sites were smpled in four periods in My nd June; in other periods fewer thn five sites were smpled ecuse of flooding, limited vilility of personnel or equipment mlfunction (Tle 11, Tle 12). Sixteen to 30 electrofishing trnsects were completed t ech site (Tle 13). Field smpling opertions in 2007 were expnded to incorporte oth the stndrd project smpling conducted in (herefter referred to s the SWG Project ) nd striped ss mrk-recpture study funded through grnt from the Stte of Connecticut Long Islnd Sound License Plte Fund (herefter referred to s the Mrk-Recpture Project ). The ojective of the Mrk-Recpture project ws to provide more detiled estimtes of striped ss undnce during spring months (My-June) in the study region, informtion tht is complementry to the SWG Project (see Ojectives 2-3). The simultneous execution of these two projects required multiple crews to operte independently in different portions of the river on the sme night. To meet this need, the UConn ot ws designted for use on the Mrk-Recpture Project, while the Smith-Root ot ws designted for use on the SWG Project. The UConn ot ws re-fitted with two spider electrode rrys, which mrkedly improved its smpling efficiency. Mrk-Recpture Project procedure clled for 3 nights ech week of night-time ot electrofishing t the Windsor Locks (WL) site. Hence the smpling schedule for oth projects required smpling t WL 4 nights ech week (Tue-Fri), with Tuesdy nights serving s dul purpose SWG Project nd Mrk- Recpture Project smple night (i.e. dt collected on this night would e used for oth projects). On SWG Project nd dul purpose nights, the SWG project smpling protocol ws followed (methods re descried in sections Ojectives 1-3). In contrst, Mrk-Recpture Project smple nights entiled only collection, mesurement (TL), nd tgging of striped ss. Decresed fish hndling times on Mrk-Recpture Project smple nights llowed for greter sptil coverge nd greter numers of tgged striped ss. Mrk-Recpture Project smple nights lso provided dditionl dt on striped ss size structure in Windsor Locks (see Ojective 2). In 2007, field smpling egn on 10 April nd ended on 15 June. We conducted smpling on 42 nights (Tle 14; 22 SWG Project, 14 Mrk Recpture Project, 6 dul purpose) nd completed 169 electrofishing trnsects (Tle 14, Tle 15, Tle 16). Equipment filure on the UConn ot necessitted chnge in smpling schedule from 24 My to the end of the seson: SWG Project smpling ws conducted Sundy through Tuesdy (EF site dropped from smpling schedule), dul purpose WL smpling ws done on Wednesdy, nd Mrk-Recpture Project smpling ws done Thursdy nd Fridy t WL. The modified schedule therefore

15 Dvis et l., Assessment of River Herring nd Striped Bss Finl Report 6 contined one fewer Mrk-Recpture Project smple night per week for the finl 3 weeks of the smpling seson nd elimintion of EF from the smpling rottion (Tle 15). The numer of trnsects completed t EF ws lower thn t other sites (Tle 16). Smpling ws discontinued fter 15 June ecuse of dditionl equipment filure, consistent low ctch rtes, nd poor nvigility stemming from low wter levels t WL. Field smpling in 2008 ws devoted entirely to the Mrk-Recpture Project. Smpling egn on 6 My nd ended on 11 June; 14 smpling trips nd 56 trnsects were completed (Tle 17, Tle 18). All smpling occurred t the Windsor Locks site. As in 2007, Mrk- Recpture Project smpling entiled only collection, mesurement (TL), nd tgging of striped ss (see Ojective 2). The Smith-Root ot ws used until 27 My, when mechnicl filure necessitted switch to the UConn ot. Smpling ws discontinued fter 11 June ecuse of mechnicl filure, low river flows, nd persistent low ctch rtes. Ojective 1: Assess Aundnce, Temporl/Sptil Distriution, nd Popultion Structure of River Herring Distriution nd undnce All cptured river herring were enumerted nd mesured for totl length (TL). All river herring were cptured vi ot electrofishing, with the exception of 4 fish tht were collected from nglers on 5/6/05. A mximum of five herring per 5 mm size clss were euthnized nd retined s su-smples for nlysis of demogrphic vriles (sex, species, ge, nd spwning history). Susmpled herring were plced on ice nd susequently dissected within 24 h. Species determintions were mde sed on peritonel color (Loesch 1987). Sex determintions were mde sed on exmintion of the gonds. Totls of 555, 1,523, nd 1,326 river herring were collected in the yers , respectively (Tle 19). Of these fish, 432, 777, nd 634 were retined s su-smples. Alewives comprised pproximtely 1-3% (n = 5 in 2005, n = 21 in 2006 nd 2007) of susmpled herring, nd were generlly collected during the erly portion of the smple seson (on or prior to 5/11) in the southern smple sites (Wethersfield nd lower Frmington River). The lone exception ws n lewife collected on 5/29/06 in Enfield. Hence, virtully ll cptured river herring were lueck herring; nlyses of reltive undnce nd size structure descried herein re referred to s pertining to lueck herring. Anlyses of ge nd spwning history structure excluded the reltively few susmpled lewives. Differences etween 2005 results nd those of susequent yers should e considered with cution ecuse of chnges in ger (UConn ot vs. Smith-Root ot) nd smpling plns (see Summry of Field Smpling Opertions). We nlyzed sptiotemporl effects on herring undnce vi nlysis of vrince (ANOVA). We first nlyzed the comined effects of site nd period, including tests for the site-period interctions (Tle 20). Becuse we were interested in the ptterns of fish undnce with regrds to the min effects, we tested for differences mong mens using multiple testing method (Tukey Studentized Rnge Test) tht controls the experimentwise error rte. We view these tests s rodly informtive; however it should e noted tht they should e viewed with cution in dtsets in which the site-period interction ws significnt, ecuse the difference etween mens of one min effect depends on the level of the other min effect. Loction hd consistent influence on the ctch rte (expressed s ctch per hour of shocking time) of herring in every yer. In ll three yers, lueck herring undnce ws highest in downriver sites. In 2005, sesonlly-verged herring undnce ws lowest t

16 Dvis et l., Assessment of River Herring nd Striped Bss Finl Report 7 Enfield nd Holyoke nd vried more thn n order of mgnitude long the river (Fig. 3). In 2006, sesonlly-verged herring undnce ws lso lowest t Enfield nd Holyoke nd gin vried more thn n order of mgnitude long the river (Fig. 4). In 2007, sesonlly-verged herring undnce ws lowest t Enfield, nd vried more thn n order of mgnitude long the river (Fig. 5). Results from Enfield in 2007 should e viewed with cution due to reltively low smpling effort t this site (Tle 16). There ws strong effect of dte on river-wide undnce of herring. In 2005, riverwide herring undnce ws highest in the erliest smpling period (Fig. 6). Severl wves of river-wide herring undnce were evident in 2006 (Fig. 7). In 2007, herring were undnt for three week period in the middle of the seson (Fig. 8). Sesonl pek rtes of ctch exceeded 100 herring per hour in 2006 nd Men herring ctch rtes hd declined elow 10 fish per hour in the lst smpling period of every yer. Size nd ge structure Men herring size vried significntly mong yers (F 2,3401 = 370, p < ). Multiple comprisons tests (Tukey) reveled tht size distriution in ech of the three yers ws significntly different from tht of other yers. Men herring size ws lrgest in 2005 (265 mm + 17 SD; Fig. 8), smllest in 2006 (244 mm + 19 SD; Fig. 10), intermedite in 2007 (256 mm + 13 SD; Fig. 11). Herring size vried within seson, nd there ws no consistent effect of loction. In ANOVA, site ws not significnt s min effect in ny yer (Tle 21). In contrst, herring size vried over the seson ech yer. In 2005 (Fig. 12) nd 2006 (Fig. 13), herring were smllest lte in the seson. In 2007 herring were smllest in lte My (Fig. 14). Scle smples nd sgittl otoliths were collected from ll lethlly susmpled lueck herring in for ge nd spwning history nlysis. Scles were tken from the re ove the lterl line nd nterior to the dorsl fin (Httl 1999). Annuli nd spwning mrks were counted from projections of scles tht were mounted etween glss microscope slides nd plced in microfiche reder (Dvis nd Schultz in press). Sgitte were plced in immersion oil nd exmined using dissecting scope t 12x mgnifiction. Otolith ge estimtes were mde in ccordnce with the methods of Liy (1985). In the cse of oth scles nd sgitte, ge ws estimted y dding 1 to the nnulus count (i.e. edge of structure considered to e finl nnulus) (Mrcy 1969; Liy 1985; Dvis nd Schultz in press). Initil nlyses focused on comprisons of ge estimtes derived from otoliths nd scles, with the gol of deciding which structure would e used s the primry structure for estimtion of popultion ge structure. A strtified rndom smple (mximum of 5 fish from ech yer/sex/cm TL strtum) of susmpled lueck herring were chosen for this nlysis (n = 247). Scle smples nd otoliths from these fish were red independently y three reders. The men stndrd devition of ge estimtes for individul fish ws clculted s mesure of inter-reder precision. Ages were then ssigned to ech smple using the following rules: in cses in which two reders greed on ge ut the third disgreed y 1 yer, the mjority ge ws ssigned to the smple; in ll other disgreement cses (three-wy disgreement or two-wy greement in which the third reder disgreed y more thn 1 yer), the smple ws removed from further nlysis. Once ges hd een ssigned, log-trnsformed length ws regressed on ge for oth otoliths nd scle ge estimtes to exmine differences in ge-length reltionships produced y the two methods. The greement etween otolith nd scle ge estimtes for individul fish ws lso exmined.

17 Dvis et l., Assessment of River Herring nd Striped Bss Finl Report 8 The men stndrd devition of ge estimtes ws 0.56 yers for otoliths nd 0.47 yers for scles, indicting higher levels of inter-reder precision in scles. The frequency distriution of stndrd devitions for oth structures shows strong mode t 0.5 yers for scles, while the distriution for otoliths is fltter nd hs longer til (Fig. 15). This result indictes tht the reltively lower levels of inter-reder precision for otoliths my e driven y smll numer of extremely noisy otoliths tht produced highly vrile ge estimtes. The slopes of the gelog length regressions produced y the two structures were similr (Fig. 16, Fig. 17; slope = 0.02 for otoliths, slope = 0.03 for scles, R 2 = 0.32 for oth reltionships). However, otolith ge estimtes were higher thn scle ge estimtes (Fig. 18). These nlyses indicte tht otoliths nd scles, while producing comprle levels of inter-reder precision, do not gree well on the ge of individul fish. We decided to proceed with otoliths s the primry structure for popultion structure nlyses, ecuse otoliths re widely considered to e more relile estimtors of ge thn scles for most fish species, especilly in older fish (Mcein et l. 2007). Otolith ge estimtes for older fish my nonetheless e erroneously high. Reders consistently reported difficulties in interpreting the edge of otoliths from lrger fish, nd estimtes greter thn 7 yers exceed pulished vlues for river herring longevity (Mrcy 1969; Loesch 1987; Jessop 2003; Dvis nd Schultz in press). In order to minimize the uncertinty ssocited with ge estimtes for lrger fish, we designted ll individuls producing ge estimtes > 5 yrs s ge 6. Becuse informtion concerning spwning history cn not e derived from otoliths, scles were used to estimte spwning history vi counts of spwning mrks. To chrcterize popultion ge structure, dditionl fish (5 fish from ech yer/sex/cm TL strtum) were rndomly selected nd dded to the initil ge susmple (n = 439 for the comined susmple). The entire susmple of otoliths ws exmined y one reder for ge estimtion. A portion (n = 245) ws screened y second reder to ssess inter-reder greement. The two reders greed on ge for 82% (n = 200) of the smples, nd disgreed y more thn one yer in < 2% (n = 4). A portion of scles in the susmple (n = 322) ws exmined y one reder for spwning history estimtion. Agreement in spwning history estimtion ws not ssessed due to high rtes of greement (> 99% greement or difference of one previous spwn) found in our previous studies of river herring scle ging (Dvis nd Schultz in press). We used ge-length keys to estimte ge structures for ech yer (Devries nd Frie 1996). We used seprte key for ech sex ecuse of previously-demonstrted differences in growth nd ge t first spwn (Loesch 1987). Sex nd ge composition of ech 10 mm size clss for ech yer ws determined from dissection nd scle nlysis. These sex-specific ge keys were then used to estimte the sex nd ge composition of the size structure smple for ech yer: F i(,) = F i * P i(,), (eqution 1) where: F i(,) = estimted numer of fish of sex nd ge in size clss i; F i = numer of fish mesured in size clss i; nd P i(,) = proportion of fish of sex, nd ge in size clss i (from dissection nd scle nlysis). The totl estimted numer of fish of ech sex nd ge within the size structure smple ws then clculted s: i F i (, ) F (,) =, (eqution 2) A spwning history/ge key ws developed for ech sex. These keys were then pplied to the estimted ge structures for ech sex to estimte the frequency of ech spwning clss within ech ge clss:

18 Dvis et l., Assessment of River Herring nd Striped Bss Finl Report 9 F,(r) = F (,) * P,(r), (eqution 3) where: F,(r) = estimted numer of fish of sex, ge in spwning history clss r; F (,) = estimted numer of fish of sex, ge (otined vi eqution 2); nd P,(r) = proportion of fish of sex, ge in spwning history clss r (from scle nlysis). The estimted numer of fish of ech sex in ech spwning history clss ws then clculted s: F, ( r) F (r) =, (eqution 4) The spwning run ws primrily composed of ges 3 6 (Figs. 19, 20). Age 2 fish were sprse nd were eliminted in nlyses of internnul vrition in ge structure. Age structures of femle (χ 2 6= 454, p < ) nd mle (χ 2 6 = 338, p < ) lueck herring differed significntly mong yers of SWG project smpling ( ). Lrge numers of ge 3 nd 4 fish were present in the 2006 nd 2007 runs, respectively, indicting strong 2003 yer clss. The 2005 run contined reltively high proportion of ge 5 nd 6 fish. The spwning run ws dominted y virgin fish in ll yers of SWG project smpling (Tle 22, Tle 23, Fig. 21, Fig. 22). Fish tht hd spwned t lest once previously were comined into single repetspwner clss in nlyses of internnul vrition in spwning history. Spwning history of femles (χ 2 2 = 25, p < ) nd mles (χ 2 2 = 50, p < ) vried mong yers of SWG project smpling. Repet-spwners (oth sexes comined) composed 30% of the 2005 run, ut then dropped to 16% of the run in 2006 nd 15% in 2007 Popultion structure nd life history of lueck herring in the Connecticut River hs chnged in recent decdes. There is single previous study of historicl popultion structure dt for lueck herring in Connecticut: Loesch (1987) reported size, ge, nd spwning history of lueck herring from the Thmes River in 1966, nd size of lueck herring from the Connecticut River in These dt were collected when river herring runs in Connecticut were reltively roust, nd therefore provide n pproprite seline to identify chnges in popultion structure tht re relevnt to recent river herring popultion declines (Dvis nd Schultz in press). We tested for differences mong historic nd contemporry mens of lueck herring size using Tukey Studentized Rnge Tests. Men lueck herring length ws 6 16% lrger in thn in (Fig. 23). Significnt differences in ge nd spwning history structures were lso evident. The Thmes River run in 1966 ws dominted y fish ge 5 nd older, nd fish younger thn ge 4 were reltively rre (Fig. 19, Fig. 20). Repet-spwners composed 82% of the 1966 run (Fig. 21, Fig. 22). Ojective 2: Assess Aundnce, Temporl/Sptil Distriution, nd Size Structure of Striped Bss Distriution nd undnce All striped ss collected on ll smpling trips were enumerted, mesured (TL), nd weighed (kg). In the first three yers of the study, ll striped ss > 300 mm TL cptured during SWG project smpling were sujected to gstric lvge to collect diet smples. No diet smples were collected during Mrk-Recpture Project smpling in In 2006 through 2008, ll striped ss > 300 mm TL (during SWG project nd Mrk-Recpture Project smpling) were lso tgged with uniquely-coded FLOY internl nchor tg (Fig. 24). These tgs fetured phone numer tht nglers could cll to report cpture of tgged striped ss. A totl of 126 striped ss ws cptured during 2005 (Tle 24). A smll numer of these fish (n = 6) were euthnized due to poor recovery from collection nd hndling. Of the