Gray Snapper Lutjanus Griseus Research Articles

A terrestrial-aquatic food web subsidy is potentially mediated by multiple predator effects on an arboreal crab

Terrestrial-aquatic food web subsidies are known to affect food web structure, ecosystem productivity, and stability of recipient habitats. This study describes a prey flux across the land–water interface associated with a behavioral response to multiple predators. Specifically, mangrove tree crabs (Aratus pisonii, hereafter Aratus) are primarily arboreal, but may jump off mangrove trees to escape avian predators, making them vulnerable to fish predation. Mesocosm experiments, field observations, and tethering assays were used to investigate behavioral responses, habitat shifts, and risk for Aratus associated with these two predator types. In the field, Aratus spent most of their time above the water on mangroves, where risk is lowest. In response to simulated bird strikes in mesocosm trials, crabs jumped off trees to escape imminent risk, and spent more time in and near the water, enhancing risk of fish predation. Fish attacks on crabs were nearly three times greater in treatments with simulated bird attacks. In addition, empirical diet data was used to examine the importance of Aratus as a prey item for a fish predator. Aratus represented up to 29% of diet by volume for one of the most common mesopredators in the Caribbean (gray snapper Lutjanus griseus), with the proportion varying greatly across space. Because Aratus consume mangrove-derived carbon, their consumption by aquatic predators represents another pathway by which mangrove production may be incorporated into aquatic food webs. These data suggest how the nexus of behavioral and food web ecology may provide for new perspectives on energy flow between ecosystems.

Diet variation of a generalist fish predator, grey snapper Lutjanus griseus, across an estuarine gradient: trade-offs of quantity for quality?

This study examined diet, prey quality and growth for a generalist fish predator, grey snapper Lutjanus griseus, at five sites across an estuarine gradient in the Loxahatchee River estuary, Florida, U.S.A. Lutjanus griseus diets shifted from dominance by low quality, intertidal crabs upstream to an increased reliance on higher quality shrimp, fishes and benthic crabs downstream. Frequency of L. griseus with empty stomachs was higher at downstream sites. Lutjanus griseus growth rates did not vary among sites. Results indicate that L. griseus may be able to compensate for lower quality prey upstream by consuming more, and thus individuals are able to maintain similar levels of energy balance and growth rates across the estuarine gradient. Elucidating mechanisms, such as compensatory feeding, that enable generalist species to remain successful across habitat conditions are critical to understanding their organismal ecology and may facilitate predictions about the response of generalists to landscape alteration.

Prey selection and functional response of juvenile lemon sharks Negaprion brevirostris

Prey preference of juvenile lemon sharks Negaprion brevirostris was examined in experiments conducted in field-based pens where the fish were offered meals of live teleosts: grey snapper Lutjanus griseus and yellow fin majorra Gerres cinereus in ratios of L. griseus:G. cinereus varying from 10:0 to 2:8. Relative electivity indices for each treatment showed that N. brevirostris preyed on G. cinereus rather than L. griseus. They showed a prey preference relating to density of G. cinereus (type II functional response) but not to L. griseus.

Using estuarine landscape structure to model distribution patterns in nekton communities and in juveniles of fishery species

Spatial relationships between distribution patterns of many species and vegetated habi- tats over multiple scales have been used in terrestrial ecosystems to help identify and map important areas for conservation and management. This approach is not widely used in characterizing habitat use of nekton species in estuaries, but it has great potential because these systems contain fairly dis- crete vegetated habitat types, and the distribution of nekton species can be influenced by the spatial arrangement of habitat. We examined the spatial relationships between estuarine habitats and nekton species to help map estuarine nekton communities for use in conservation planning. Using a Geographic Information System (GIS), we measured area (m 2 ) and edge density (m km -2 ) of estuar- ine habitats over multiple scales in Charlotte Harbor, Florida (USA). We used redundancy analysis (RDA) to examine spatial patterns of nekton community composition, habitat, and local habitat characteristics. RDA revealed that spatial patterns in nekton community composition were most highly correlated with distance from the nearest pass to the Gulf of Mexico (r = -0.97) and with salinity (r = 0.94) and area of continuous seagrass habitat (r = 0.91). We used GIS maps of 2 variables (distance from the nearest pass and area of continuous seagrass habitat) to model spatial patterns in nekton community composition and the distribution of several juveniles of fishery species (red drum Sciaenops ocellatus, gray snapper Lutjanus griseus, lane snapper L. synagris, sand seatrout Cynoscion arenarius, and spotted seatrout C. nebulosus). The results suggest that incorporating measures of habitat area (over multiple scales) and spatial position into spatial models of nekton distribution is useful in conservation and management planning.