Foraging Behavior and Monetary Impact of Wading Birds at Arkansas Baitfish Farms

WP rnnrlurted fnraging ob,ervations, food habits studie~, and producer aurveys to determine the foraging behavior and monetary impact of great blue herons Ardca hr.rodia5, great egrets A . alba, and little blue heron5 E m t r a cnurulua loragine at Arkansas haiffish farms. Although great egrets captured most baitfishlminute, captureslstrike were nearlj identical among the three wadine bird snecies. American eizzard shad Dorosoma crordinnum. eoldfish Carossius nuratul. D . and giant water bugs Hemiplera: Beloston~atidae were collected from the gastro-intestinal tract of grent blue herons. Only golden shiners ,Votrrni~onu,~ crysoleucur and goldfish were found in great egrets. We found dragonflies Odonaro, golden shiners, green sunfish Lepomis cyancllus, and water bugs in little blue herons. In contrast to other birds collected, snowy egrets E. thula were found to contain mosquito fish Gornburiu ujfinb. Among 2,742 teleost otoliths recovered from collected great blue herons. great egrets, and little blue herons, most otoliths belonged to the Cyprinidae family (including the baiffishes). Surveyed farm managers use various auditory 2nd visual stinluli to disperse fish-eating birds from their farms. Surveyed baitfish farnlers suggested that the average cost of their annual bird harassment program was $11,580 at relatively small farm> (< 202 ha) and $104,560 at relatively larce (2 202 ha) baiffish aquaculture facilities. &? estimated the . replacemeut cost of baitfish consumed by wading birds based upon their daily food requiren~ents, the food habits of herons and eerets at baiffish farms. the hvootheticnl abundance of wadine birds , . at a particular baiffish farm (relative to surrey results), the duration of herons and egrets reported by farm managers, and current baiffish market values. Aquaculture in the United States presently involves over 4,000 individual farms, with total salcs exceeding 5975 millionlyr ( U S D A 'Corre.~p-ponding i iuihori prcrcnr ilddrrir. L'nried S1ulr.r Depirrirnenr oJ Apricu/iurr. i t~ i rnu l und Pla~ir Hculiii Inspfl~ion Serricc Wi/dl! /r Seiv~crr Vurional WiIdliJe Resrord Crrirer. 4101 LuPorre Avenue. Furl Collins, Coiunrdo ROS2I-?IS4 L:SA. 'Preruni addru~s. Lhirrd Siuirr F i i l ) onl/ W8'iiil/p Service. Kentucky Fidii Olhic 7 6 1 Georgcios,i Roud Frunkfori, Kenruck) 40601 L S.4 'Pruscnl addrvsr L i i t r e d Srurr, Drporir?ivnr of Inirrritr Bureuu 01' Indiun .4J]"tr~, f i ~ l ~ i f i c R~gionul Ofire-Bnin</l r f l Furtrrru 2800 Cuiiuge Wu?, Lii.rurnunro, Colilr,mio VV25 LT.4. 2000). According to this 1998 census, the two states with greatest aquaculture sales lire Mississippi (S290 million of catfish) and Arkansas (584 million of catfish and baitfish). Although haitfish are cultured throughout Arkanssa. the production of golden shiners 1Votewrixr1nrr~ c r y s o i r u c u s , goldfish Cclrclssius uururus . and Fathead minnows P i m ? p ! ~ u l r s p r o m e l u s is prin~arily located in central Arkansas, east of Little Rock (Lonoke and Prairie counties). In 1980, approximately 6,400 h a were used for baitfish production in Arkansas (Y3'!/4 golden shiners, 10% idthead minnows. 7% goldfish). By 1995, the Arkansas boitfish industry had C Copir~ghr bv the World Aquacullurc P o c ~ e ~ ~ 2005 UADIUG BIRDS 4T ARKANS9S BUTFISH F4RbIS 3 5 5 grown to approximately 12,100 ha (64'h golden shiners. 16Yu fathead rninnoirs. 20:!~ goldfish: N. Stone, University of Arkansas-Pine Bluff. unpublished data). Approximately 4S and 16'!6 of these Arkansas baitfish farms are located in Lonohc auil Plailic cuur~lica, respectively (C. Collins. USDAIARS1H.K. Dupree National Aquaculture Research Center, unpublished ddta). North American aquaculture facilities provide potential inland foraging sites for many species of fish-eating birds. Much research has focused on the impacts of double-crested cormorants Plroiucr~~~~orax auri!ir.r (Stickley et al. 1992; Glahn and Brugger 1995; Glahn and Stickle) 1995; Glahn and Dorr 2002). great blue herons .Ardea lrerodius (Ross 1994; Stickley et al. 1995; Glahn et al. 1999b. 2000. 2002), Al t lc~ica~l whilc pclicans Pelecarlirs erythrorliw~clros (King and Werner 2001; King and Ivlichot 2002), and great egrets A. alba (Ross 1994; Glahn et al. 1999b; Werner et al. 20111) to catfish aquacultul-e. Although the food habits of diving ducks at baitfish aquaculture facilities have been recently investigated (U'ooten and Werner 2004), few studies have addressed the foraging ecology of herons and egrets associated with baitfish production (Hoy et al. 1989; Hoy 1994). The overall monetary impact of bird depredation includes the cost of replacing consumed baitfish and the cost of harassing fish-eating birds. The development of cost-effective management strategies is contingent upon reconciling these costs with resultant baittish production. The objectives of this study were to lnvestlgate the fbraging behavior and monetary impacts of herons and egrets at baitfish aquaculture facilities in Arkansas. Materials and Methods herons (observed among 4 d and five farms), great egrets (5 d. five farms), and little blue herons Exreria cueriilca (6 d , four farms). Using binoculars and spotting scopes. observers recorded the date, farm name. species, bird age (immature, adult, unknown [based on plumage and bare parts]; Palmer lY l b , Vois~n 1YYIj. number of fish captures. number of strikes, foragiug time (? 1 min), and whether birds were disturbed (by farm workers via fish feeding andlor bird harassment) during each foraging observation. Observation data were surnrnarized to estimate average captureslstrike. strikesimin, and captureaimin for each wading bird speciss. We estimated the average time of foraging bouts and cap~ureslforaging bout using only foraging observations that were not terminated by disturbance.