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2013 SOUTHEASTERN NATURALIST 12(1):233–237
Diet of Juvenile Alabama Shad (Alosa alabamae) in Two
Northern Gulf of Mexico Drainages
Paul F. Mickle1,*, Jacob F. Schaefer2, Donald A. Yee2, and Susan B. Adams3
Abstract - 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 <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 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.
Alosa alabamae Jordan and Evermann (Alabama Shad) is an anadromous
species, reproducing in northern Gulf of Mexico river drainages during spring
and spending the first summer and fall in rivers before moving into the Gulf of
Mexico (Mettee and O’Neil 2003). As age-0 Alabama Shad grow, habitat preferences
tend to shift from sand bar to open channel and steep bank habitats (Mickle
et al. 2010). One might expect shifts in diet to coincide with the observed change
in habitat use and juvenile size.
Currently, the Alabama Shad is listed as endangered by the International
Union for the Conservation of Nature (IUCN) and threatened by the American
Fisheries Society (Meadows et al. 2006). Many states including Alabama, Arkansas,
Florida, Georgia, Kentucky, Louisiana, Mississippi, and Missouri list the
Alabama Shad as a species of greatest conservation need (Meadows et al. 2006).
The specific objectives of this paper were to determine if juvenile Alabama Shad
diets change as they mature and whether diets differ between drainages.
1The University of Southern Mississippi, Department of Coastal Sciences, 703 East
Beach Drive, #5118, Ocean Springs, MS 39564-5118. 2The University of Southern Mississippi,
Department of Biological Sciences, 118 College Drive #5018, Hattiesburg, MS
39406-5018. 3USDA Forest Service, Southern Research Station, 1000 Front Street, Oxford,
MS 38655. *Corresponding author - email@example.com.
234 Southeastern Naturalist Vol. 12, No. 1
Fish collections were conducted with an electrofishing boat during June
and October of 2007 and 2008 in the Pascagoula (10 sites) and Apalachicola
(4 sites) river basins. The stomachs and lower intestines of collected Alabama
Shad were excised, and food items were preserved in 10% formalin. Stomach
contents from all Alabama Shad were initially identified and categorized as
unidentifiable organics, algae, insect, or fish using a dissecting microscope at
16x power. Insect and fish items were then identified further to order or appropriate
lower taxonomic level using aquatic and terrestrial insect keys and
counted (Merritt and Cummins 1984, 1995; Voshell 2002). Fifteen percent of
the items were quality-checked using blind validation by professional taxonomists.
Alabama Shad collected were separated into four different size groups
(<50 mm, 50–70 mm, >70–90 mm, >90 mm) based on a previous ontogenetic
study in which these size groups were found in different habitats (Mickle et
In total, 211 juvenile Alabama Shad were collected: 115 from the Pascagoula
River, and 96 from the Apalachicola River. Stomach contents from
Alabama Shad <50 mm SL (n = 47, Pascagoula River only) were primarily
unidentifiable organics (Fig. 1), including semi-decomposed algae and various
other materials that were not further identified. Of the remaining 164 fish >50
mm, 76 Alabama Shad (46%) had stomach contents that were identifiable. Diet
items within the >50 mm Alabama Shad stomachs included the orders Coleoptera
(aquatic lifestage), Diptera (terrestrial lifestage), Ephemeroptera (aquatic
lifestage), Hemiptera (terrestrial lifestage), Hymenoptera (aquatic lifestage),
Lepidoptera (terrestrial lifestage), Odonata (aquatic lifestage), and Orthoptera
(terrestrial lifestage). Although sampling was conducted in the large tributaries
as well as the mainstem in the Pascagoula basin, diet items did not differ
between tributary and mainstem sites as compared in exploratory analysis, so
samples were combined.
Most of the stomach contents of Alabama Shad <50 mm were unidentifiable
organics, suggesting filter feeding or particulate feeding of smaller prey
(Fig. 1). It should be pointed out that all fish <50 mm were collected exclusively
in the Pascagoula River. The Pascagoula River fish displayed a decreasing
trend of the unidentified organics and algae similar to the Apalachicola population,
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 River
displayed large occurrences of terrestrial insects within their stomachs, whereas
the Pascagoula River showed both terrestrial and aquatic insects dominating
the two largest size classes, >70–90 mm and >90 mm (Fig. 1). Terrestrial insects
dominated all size groups of shad collected in the Apalachicola Rivers,
with unidentified organics and algae becoming less present with increasing fish
2013 P.F. Mickle1, J.F. Schaefer, D.A. Yee, and S.B. Adams 235
Figure 1. Percent occurrence of aquatic invertebrates (overall classification by Merritt
and Cummins 1984), terrestrial invertebrates (overall classification by Merritt and Cummins
1984), unidentified organics and algae, or fish diet items found within the four size
classes of juvenile Alabama Shad from the Apalachicola (A) and Pascagoula (B) rivers.
236 Southeastern Naturalist Vol. 12, No. 1
size. Only one fish (Ammocrypta beani Jordan [Naked Sand Darter]) was found
in the stomach of a juvenile Alabama Shad and it occurred in the largest size
group from the Pascagoula River. This finding was unexpected as the Alabama
Shad has a terminal mouth, which is not associated with benthic feeding, while
Naked Sand Darters are benthic. No fish were found in any other size groups
(Fig. 1), which may be due to gape limitation.
Although small and large juvenile Alabama Shad ingested different orders of
insects, the variability of diet within the size groups was comparable, which suggests
that they are generalist insect feeders. The larger Alabama Shad had a diet
dominated by Ephemeroptera nymphs. This order possesses almost exclusively
aquatic juvenile larvae that emerge in open water where the large Alabama Shad
were collected (Merritt and Cummins 1984). The habitat shift seen in age-0 Alabama
Shad may be driving the observed diet shift and would be consistent with
a generalist diet strategy. Similar findings were shown with Etheostoma rubrum
Raney & Suttkus (Bayou Darter), in which the diet shifted to match changes in
food availability (Knight and Ross 1994).
Food webs within river drainages are complex and highly variable in relation
to season and flow (Power and Dietrich 2002). Optimal-foraging theory
predicts that animals should select the most profitable prey items and only
specialize if the types of prey items differ markedly in overall profitability
(energy gain minus search, capture, and handling costs) (Futuyma and
Moreno 1988). If prey items are all of similar profitability, the theory predicts
an animal will forage in a manner that minimizes search time by consuming
any prey item encountered (e.g., a generalist feeding strategy). In that case,
variability in the abundance or distribution of prey items will be most influential
in determining diet and may result in a broad diet (Futuyma and Moreno
1988). Many insectivorous stream fishes feed on a wide variety of insects but
may specifically key in on the currently most abundant items. Variability is
usually present, but the strategy may be closer to that of a specialist during
brief temporal cycles. Within variable systems such as Gulf Coastal Plain
rivers, a generalist strategy may be more advantageous for first-year growth.
Diet was variable between drainages and size classes, which was consistent
with the fish feeding opportunistically on prey items most available. This
finding was consistent with the basic optimal-foraging theory fitting a generalist
strategy. Specialist strategies would be expected to be seen in very stable
systems where competition is intense (i.e., niche compression; Holling 1973,
Stahl and Stein 1994). Patterns of prey availability in these coastal plain
drainages may be quite stochastic, which is expected to reduce competitive
interactions that would favor more of a specialist strategy.
Although this species exhibits a generalist diet strategy, food-item diversity
may be crucial to compensate for the ontogenetic changes that are occurring for
2013 P.F. Mickle1, J.F. Schaefer, D.A. Yee, and S.B. Adams 237
age-0 Alabama Shad. To properly conserve this rare species, the food webs of
native rivers must be protected. These variable systems must have multiple food
items from different sources that fish species can utilize. In order to conserve
Alabama Shad, managers must monitor the habitats, water quality, and resources
that this species is using during the first year of life.
We thank The University of Southern Mississippi (USM) Department of Biological
Sciences and the United States Forest Service (USFS) for providing vehicles and boats;
Sarah Ashworth (USM Department of Coastal Sciences) for editing; Jeremiah Estes and
Amy Wilberding (USM Department of Biology) for diet validation; and, Rick Long,
Anthony Knapp, and Caleb Purtlebaugh (Florida Fish and Wildlife Conservation Commission)
for helping with field collections. Funding was provided by NOAA Fisheries
(0-2003-SER1), the Mississippi Department of Wildlife, Fisheries, and Parks (SWG04),
the USFS Southern Research Station (SRS 03-CA-11330127-262), and the American
Sportfishing Association Fish America Foundation (FAF-4078R).
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