Foraging patterns of two syngnathid fishes: importance of harpacticoid copepods

Abstract

The diets of juvenile (<g0 mm) Syngnathus scovelli and of H~ppocampus zosterae, abundant members of a resident fish community in a Thalassia testudnum seagrass bed in Tampa Bay, Florida, were examined from Apnl to October 1984. Harpacticoid copepods comprised most of the diet, both in terms of percent number and percent biomass, for the smaller size classes of S. scovelli and for H. zosterae, and harpacticoids generally had the highest index of relative importance (IRI) for both syngnathids. S. scovelli displayed ontogenetic switching to larger food items, such as amphipods. shrimp and crustacean eggs. Harpacticus sp. 1 was the most common harpacticoid copepod species found in the guts of the 2 syngnathids, but was only rarely encountered in prey samples from seagrass blades. Three other harpacticoids, Paradactylopodia brevicornis sp., Dactylopodia tisboides and Harpacticus sp. 2 had high IRIS in H. zosterae but not in S. scovelli. Vanderploeg & Scavia's selectivity index (E') was calculated for sampling dates when both species of syngnathids were most abundant, using prey density on seagrass blades as a measure of prey avadabhty. Only the harpacticoid Harpacticus sp.

Assessing diet composition of seahorses in the wild using a non destructive method: Hippocampus reidi (Teleostei: Syngnathidae) as a study-case

“…The occasional consumption of insects (ants) observed in this study is unique, and is possibly related to the massive presence of mangrove trees along the margins of the estuary. While Harpacticoida was the principal item consumed by Hippocampus zosterae (Tipton & Bell, 1988), H. subelongatus (Kendrick & Hyndes, 2005) and H. reidi (this study), the other studied seahorse species mostly consumed Cyclopoida copepods, amphipods and caridean shrimps (see Kanou & Kohno, 2001;Kendrick & Hyndes, 2005;Teixeira & Musick, 2001;Burchmore et al, 1984;Woods, 2002). These results highlight the importance of crustaceans as a prey category to seahorses.…”

“…harpacticoid copepods, nematodes, polychaetes) by H. reidi has also been recorded for H. whitei, H. zosterae, H. abdominalis, H. breviceps, and H. subelongatus, which mainly consumed epibenthic invertebrates (Burchmore et al, 1984;Tipton & Bell, 1988;Woods, 2002;Kendrick & Hyndes, 2005), and possibly reflect the sedentary behaviour of seahorses, rather than a gape limitation.…”

“…while mid size and larger specimens fed almost exclusively on amphipods (Teixeira & Musick, 2001). Additionally, Tipton & Bell (1988) found an increase in the consumption of amphipods by larger specimens of H. zosterae, despite the dominance of harpacticoid copepods in all size classes, and Kanou & Kohno (2001) reported that juveniles H. mohnikei exhibited a division of prey items between size classes, with the smaller seahorses feeding mainly on cyclopoid copepods smaller than those consumed by larger specimens. Some authors state that the reproductive system of Syngnathidae may result in differential reproductive costs, which may be reflected in different prey selection by males and females (Svensson, 1988;Steffe et al, 1989;Lyons & Dunne, 2003;Garcia et al, 2005).…”

“…Nevertheless, similar to what has been recorded for S. typhle (Oliveira et al, 2007), our findings suggest that H. reidi may have a specialist strategy in early life stages, consuming only small planktonic prey, and then becoming a moderately generalized benthonic predator. According to Foster & Vincent (2004), seahorses may change their diet ontogenetically, or as they grow, which may be a reflection of changes in feeding capabilities (e.g., change in mouth gape) and/or habitat shifts (Ryer & Orth, 1987;Tipton & Bell, 1988;Woods, 2002).…”

“…Published data on the diet composition of seahorses from field-based studies, however, are limited to a few species (Tipton & Bell, 1988;Kanou & Kohno, 2001; Texeira & Musick, 2001;Woods, 2002;Kendrick & Hyndes, 2005), and typically based on destructive sampling.…”