Useofsandwavehabitatsbysilverhake P. J. AUSTER * †, J. L INDHOLM * ‡,S.S CHAUB *,G.F UNNELL ‰, L.S.K AUFMAN { AND P. C.VALENTINE ** *NationalUnderseaResearchCenter,UniversityofConnecticutatAveryPoint,Groton, CT06340,U.S.A.; ‡StellwagenBankNationalMarineSanctuary,175EdwardFoster Road,Scituate,MA02066,U.S.A.; ‰NationalInstituteofWaterandAtmospheric Research,P.O.Box11-115,Hamilton,NewZealand; {BiologyDepartment,Boston University,Boston,MA02215,U.S.A.and**U.S.GeologicalSurvey, WoodsHole,MA02543,U.S.A. (Received 29 April 2002, Accepted 4 November 2002) Silver hake Merlucciusbilinearis are common members offish communities in sandwavehabitats on Georges Bank and on Stellwagen Bank in the Gulf of Maine. Observations of fish size v . sand wave period showed that silver hake are not randomly distributed within sand wave landscapes. Regression analyses showed a significant positive relationship between sandwave period and fish length. Correlation coefficients, however, were low, suggesting other interactions with sand wave morphology, the range ofcurrent velocities, and available prey may also influence their dis- tribution. Direct contact with sand wave habitats varied over diel periods, with more fish resting ontheseafloorduringdaytimethanatnight.Socialforaging,intheformofpolarizedgroupsoffish swimming in linear formations during crepuscularand daytime periods, was also observed. Sand wavehabitatsmayprovideshelterfromcurrentflowsandmediatefish^preyinteractions. # 2003TheFisheriesSocietyoftheBritishIsles Key words: behaviour; flow refuges; landscape; Merlucciusbilinearis; social foraging; video. INTRODUCTION Silver hake Merlucciusbilinearis (Mitchill) are distributed on the continental shelf of eastern North America from southern Newfoundland to South Carolina, occurring from below the tide line to over a depth of 910m (Bigelow & Schroeder, 1953; Scott & Scott, 1988). Early benthic phase juveniles are 17^20mm standard length ( L S ) at settlement (Fahay, 1974). Size at 50% maturity is c. 23 cm off the north-east U.S.A. (O’Brien etal.,1993). Silver hake are important predators in the outer continental shelf fish community, feeding on amphipods and shrimp when small and becoming nearly all piscivorous as they grow (Bowman, 1984; Scott & Scott,1988). Approximately 74% of the diet of adult silver hake on Georges Bank is composed offishes and squid (Cohen & Grosslein,1987). †Author to whom correspondence should be addressed. Tel.: þ1 8604059121; fax: þ1 8604452969; email:auster@uconn.edu JournalofFishBiology (2003) 62, 143^152 doi:10.1046/j.0022-1112.2003.00016.x,availableonlineathttp://www.blackwell-synergy.com 143 # 2003TheFisheriesSocietyoftheBritishIsles