Understanding food-web ecology is valuable to conservation by linking interactions of multiple species together and illustrating the functionality of trophic exchange. Alosa alabamae (Alabama Shad), an anadromous species, reproduces in northern Gulf of Mexico drainages from February through May, and for this study, the Pascagoula and Apalachicola rivers were chosen to sample juvenile Alabama Shad. The age-0 fish mature within these rivers and have the potential to impact the food web of the systems in which maturation occurs. The focus was to determine if diet changes as Alabama Shad mature, and to identify diet differences between drainages. Diets of Alabama Shad (SL) consisted primarily of a dark, almost black material labeled as unidentifiable organics. while larger Alabama Shad. \u3e50 mm SL, fed almost exclusively on insects. Many groups of aquatic and terrestrial insects were found in the stomachs of this species. Alabama Shad diets also differed among drainages, with the Apalachicola River being dominated by terrestrial insects, and the Pascagoula River having both terrestrial and aquatic insects. Diet and trophic placement of Alabama Shad may allow managers to understand the importance of this fish within its natal rivers

Adams, Susan B.

Mickle, Paul F.

Schaefer, Jacob F.

Yee, Donald A.

English

Aquila Digital Community

The University of Southern MississippiThe Aquila Digital CommunityFaculty Publications4-1-2013Diet of Juvenile Alabama Shad (Alosa alabamae) inTwo Northern Gulf of Mexico DrainagesPaul F. MickleUniversity of Southern Mississippi, Paul.Mickle@usm.eduJacob F. SchaeferUniversity of Southern Mississippi, Jake.Schaefer@usm.eduDonald A. YeeUniversity of Southern Mississippi, donald.yee@usm.eduSusan B. AdamsUSDA Forest ServiceFollow this and additional works at: https://aquila.usm.edu/fac_pubsPart of the Biology CommonsThis Article is brought to you for free and open access by The Aquila Digital Community. It has been accepted for inclusion in Faculty Publications byan authorized administrator of The Aquila Digital Community. For more information, please contact Joshua.Cromwell@usm.edu.Recommended CitationMickle, P. F., Schaefer, J. F., Yee, D. A., Adams, S. B. (2013). Diet of Juvenile Alabama Shad (Alosa alabamae) in Two Northern Gulf ofMexico Drainages. Southeastern Naturalist, 12(1), 233-237.Available at: https://aquila.usm.edu/fac_pubs/78022013 SOUTHEASTERN NATURALIST 12(l):233-237Diet of Juvenile Alabama Shad {Alosa alabamae) in TwoNorthern Gulf of Mexico DrainagesPaul F. Mickle'*, Jacob F. Schaefer^ Donald A. Yee^ and Susan B. Adams^Abstract - Understanding food-web ecology is valuable to conservation by linkinginteractions of multiple species together and illustrating the functionality of trophicexchange. Alosa alabamae (Alabama Shad), an anadromous species, reproduces innorthern Gulf of Mexico drainages from February through May, and for this study, thePascagoula and Apalachicola rivers were chosen to sample juvenile Alabama Shad.The age-0 fish mature within these rivers and have the potential to impact the foodweb of the systems in which maturation occurs. The focus was to determine if dietchanges as Alabama Shad mature, and to identify diet differences between drainages.Diets of Alabama Shad <50 mm standard length (SL) consisted primarily of a dark,almost black material labeled as unidentifiable organics, while larger Alabama Shad,>50 mm SL, fed almost exclusively on insects. Many groups of aquatic and terrestrialinsects were found in the stomachs of this species. Alabama Shad diets also differedamong drainages, with the Apalachicola River being dominated by terrestrial insects,and the Pascagoula River having both terrestrial and aquatic insects. Diet and trophicplacement of Alabama Shad may allow managers to understand the importance of thisfish within its natal rivers.IntroductionAlosa alabamae Jordan and Evermann (Alabama Shad) is an anadromousspecies, reproducing in northern Gulf of Mexico river drainages during springand spending the first summer and fall in rivers before moving into the Gulf ofMexico (Mettee and O'Neil 2003). As age-0 Alabama Shad grow, habitat prefer-ences tend to shift from sand bar to open channel and steep bank habitats (Mickleet al. 2010). One might expect shifts in diet to coincide with the observed changein habitat use and juvenile size.Currently, the Alabama Shad is listed as endangered by the InternationalUnion for the Conservation of Nature (IUCN) and threatened by the AmericanFisheries Society (Meadows et al. 2006). Many states including Alabama, Ar-kansas, Florida, Georgia, Kentucky, Louisiana, Mississippi, and Missouri list theAlabama Shad as a species of greatest conservation need (Meadows et al. 2006).The specific objectives of this paper were to determine if juvenile Alabama Shaddiets change as they mature and whether diets differ between drainages.'The University of Southern Mississippi, Department of Coastal Sciences, 703 EastBeach Drive, #5118, Ocean Springs, MS 39564-5118. 'The University of Southern Mis-sissippi, Department of Biological Sciences, 118 College Drive #5018, Hattiesburg, MS39406-5018. ^USDA Forest Service, Southern Research Station, 1000 Front Street, Ox-ford, MS 38655. 'Corresponding author - paul.micklc@usm.edu.234 Southeastern Naturalist ' ' Vol. 12, No. 1MethodsFish collections were conducted with an electrofishing boat during Juneand October of 2007 and 2008 in the Pascagoula (10 sites) and Apalachicola(4 sites) river basins. The stomachs and lower intestines of collected AlabamaShad were excised, and food items were preserved in 10% formalin. Stomachcontents from all Alabama Shad were initially identified and categorized asunidentifiable organics, algae, insect, or fish using a dissecting microscope at16x power. Insect and fish items were then identified further to order or ap-propriate lower taxonomic level using aquatic and terrestrial insect keys andcounted (Merritt and Cummins 1984, 1995; Voshell 2002). Fifteen percent ofthe items were quality-checked using blind validation by professional taxono-mists. Alabama Shad collected were separated into four different size groups(<50 mm, 50-70 mm, >70-90 mm, >90 mm) based on a previous ontogeneticstudy in which these size groups were found in different habitats (Mickle etal. 2010).ResultsIn total, 211 juvenile Alabama Shad were collected: 115 from the Pas-cagoula River, and 96 from the Apalachicola River. Stomach contents fromAlabama Shad <50 mm SL {n = 47, Pascagoula River only) were primarilyunidentifiable organics (Fig. 1), including semi-decomposed algae and variousother materials that were not further identified. Of the remaining 164 fish >50mm, 76 Alabama Shad (46%) had stomach contents that were identifiable. Dietitems within the >50 mm Alabama Shad stomachs included the orders Coleóp-tera (aquatic lifestage), Diptera (terrestrial lifestage), Ephemeroptera (aquaticlifestage), Hemiptera (terrestrial lifestage), Hymenoptera (aquatic lifestage),Lepidoptera (terrestrial lifestage), Odonata (aquatic lifestage), and Orthoptera(terrestrial lifestage). Although sampling was conducted in the large tributar-ies as well as the mainstem in the Pascagoula basin, diet items did not differbetween tributary and mainstem sites as compared in exploratory analysis, sosamples were combined.Most of the stomach contents of Alabama Shad <50 mm were unidentifi-able organics, suggesting filter feeding or particulate feeding of smaller prey(Fig. 1). It should be pointed out that all fish <50 mm were collected exclusive-ly in the Pascagoula River. The Pascagoula River fish displayed a decreasingtrend of the unidentified organics and algae similar to the Apalachicola popula-tion, with both terrestrial and aquatic insects increasing in the 50-70 mm and>70-90 mm size groups (Fig. 1). All size classes in the Apalachicola Riverdisplayed large occurrences of terrestrial insects within their stomachs, whereasthe Pascagoula River showed both terrestrial and aquatic insects dominatingthe two largest size classes, >70-90 mm and >90 mm (Fig. 1). Terrestrial in-sects dominated all size groups of shad collected in the Apalachicola Rivers,with unidentified organics and algae becoming less present with increasing fish2013 P.F. Micklel, J.F. Schaefer, D.A. Yee, and S.B. Adams 23570CDoc60 -50 H40 -ÜÜO"c 30(DCD20 ^10 -Aquatic • .TerrestrialUnidentifiable OrganicsFish50-70 >70-90 >90Juvenile Alabama Shad Size Classes (mm)5040 -<DÜiooo§ 20CDû.10 -i|—aCZZ]AquaticTerrestrialUnidentifiableFishOrganics<50 50-70 >70-90 >90Juvenile Alabama Shad Size Classes (mm)Figure 1. Percent occurrence of aquatic invertebrates (overall classification by Merrittand Cummins 1984), terrestrial invertebrates (overall classification by Merritt and Cum-mins 1984), unidentified organics and algae, or fish diet items found within the four sizeclasses of juvenile Alabama Shad from the Apalachicola (A) and Pascagoula (B) rivers.236 Southeastern Naturalist • Vol. 12, No. 1size. Only one fish {Ammocrypta beani Jordan [Naked Sand Darter]) was foundin the stomach of a juvenile Alabama Shad and it occurred in the largest sizegroup from the Pascagoula River. This finding was unexpected as the AlabamaShad has a terminal mouth, which is not associated with benthic feeding, whileNaked Sand Darters are benthic. No fish were found in any other size groups(Fig. 1), which may be due to gape limitation.DiscussionAlthough small and large juvenile Alabama Shad ingested different orders ofinsects, the variability of diet within the size groups was comparable, which sug-gests that they are generalist insect feeders. The larger Alabama Shad had a dietdominated by Ephemeroptera nymphs. This order possesses almost exclusivelyaquatic juvenile larvae that emerge in open water where the large Alabama Shadwere collected (Merritt and Cummins 1984). The habitat shift seen in age-0 Ala-bama Shad may be driving the observed diet shift and would be consistent witha generalist diet strategy. Similar findings were shown with Etheostoma rubrumRaney & Suttkus (Bayou Darter), in which the diet shifted to match changes infood availability (Knight and Ross 1994).Food webs within river drainages are complex and highly variable in rela-tion to season and flow (Power and Dietrich 2002). Optimal-foraging theorypredicts that animals should select the most profitable prey items and onlyspecialize if the types of prey items differ markedly in overall profitabil-ity (energy gain minus search, capture, and handling costs) (Futuyma andMoreno 1988). If prey items are all of similar profitability, the theory predictsan animal will forage in a manner that minimizes search time by consumingany prey item encountered (e.g., a generalist feeding strategy). In that case,variability in the abundance or distribution of prey items will be most influen-tial in determining diet and may result in a broad diet (Futuyma and Moreno1988). Many insectivorous stream fishes feed on a wide variety of insects butmay specifically key in on the currently most abundant items. Variability isusually present, but the strategy may be closer to that of a specialist duringbrief temporal cycles. Within variable systems such as Gulf Coastal Plainrivers, a generalist strategy may be more advantageous for first-year growth.Diet was variable between drainages and size classes, which was consistentwith the fish feeding opportunistically on prey items most available. Thisfinding was consistent with the basic optimal-foraging theory fitting a gener-alist strategy. Specialist strategies would be expected to be seen in very stablesystems where competition is intense (i.e., niche compression; Holling 1973,Stahl and Stein 1994). Patterns of prey availability in these coastal plaindrainages may be quite stochastic, which is expected to reduce competitiveinteractions that would favor more of a specialist strategy.Although this species exhibits a generalist diet strategy, food-item diversitymay be crucial to compensate for the ontogenetic changes that are occurring for2013 • P.F. Mieklel, J.F. Schaefer, D.A. Yee, and S.B. Adams 237age-0 Alabama Shad. To properly conserve this rare species, the food webs ofnative rivers must be protected. These variable systems must have multiple fooditems from different sources that fish species can utilize. In order to conserveAlabama Shad, managers must monitor the habitats, water quality, and resourcesthat this species is using during the first year of life. •AcknowledgmentsWe thank The University of Southern Mississippi (USM) Department of BiologicalSciences and the United States Forest Service (USFS) for providing vehicles and boats;Sarah Ashworth (USM Department of Coastal Sciences) for editing; Jeremiah Estes andAmy Wilberding (USM Department of Biology) for diet validation; and. Rick Long,Anthony Knapp, and Caleb Purtlebaugh (Florida Fish and Wildlife Conservation Com-mission) for helping with field collections. Funding was provided by NOAA Fisheries(0-2003-SERl), the Mississippi Department ofWildlife, Fisheries, and Parks (SWG04),the USFS Southern Research Station (SRS 03-CA-11330127-262), and the AmericanSportñshing Association Fish America Foundation (FAF-4078R).Literature CitedFutuyma. D.J., and G. Moreno. 1988. The evolution of ecological specialization. AnnualReview of Ecology and Systematics 19:207-233.Holling, E.G. 1973. Resilience and stability of ecological systems. Annual Review ofEcology and Systematics 4:1-23.Knight, G.J., and S.T. Ross. 1994. Feeding habits of the Bayou Darter. Transactions ofthe American Fisheries Society 123:794-802.Meadows, D.W., S.B. Adams, and J.F. Schaefer. 2006. Threatened fishes of the world:Alosa alabamae (Jordan and Evermann, 1896) (Clupeidae). Environmental Biologyof Fishes 82:173-174.Mettee, M.F., and P.E. O'Neil. 2003. Status of Alabama Shad and Skipjack Herring inGulf of Mexico drainages. Pp. 157-170, In K. Limburg and J. Waldman (Eds.). Bio-diversity, Status, and Conservation of the World's Shads. American Fisheries SocietySymposium 35, Bethesda, MD.Merritt, R. W., and K. W. Cummins. 1984. An Introduction to the Aquatic Insects of NorthAmerica. Kendall/Hunt, Dubuque, IA. 722 pp.Merritt, R.W., and K.W. Cummins. 1995. An Introduction to the Aquatic Insects of NorthAmerica. Third Edition. K.endall/Hunt, Dubuque, IA. 862 pp.Mickle, P.F., J.F. Schaefer, S.B. Adams, and B.R. Kreiser. 2010. Habitat use of age-0 Ala-bama Shad in the Pascagoula River drainage, USA. Journal of Ecology of FreshwaterFish 19:107-115.Power, M.E., and W.E. Dietrich. 2002. Food webs and river networks. Ecological Re-search 17:451-471.Stahl, T.P., and R.A. Stein. 1994. Inñuence of larval Gizzard Shad {Dorosoma ce-pedianum) density on piscivory and growth of young-of-year Saugeye {Stizoste-dion vitreum x S. canadense). Canadian Journal of Fisheries and Aquatic Sciences51(9): 1993-2002.Voshell, R.R. 2002. A Guide to Common Freshwater Invertebrates of North America.McDonald and Woodward, Granville, OH. 456 pp.Copyright of Southeastern Naturalist is the property of Humboldt Field Research Institute and its content maynot be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express writtenpermission. However, users may print, download, or email articles for individual use.

Diet of Juvenile Alabama Shad (Alosa alabamae) in Two Northern Gulf of Mexico Drainages

https://aquila.usm.edu/cgi/viewcontent.cgi?article=8969&context=fac_pubs

Diet of Juvenile Alabama Shad (Alosa alabamae) in Two Northern Gulf of Mexico Drainages

Abstract

Similar works

Full text

Available Versions

Aquila Digital Community