Life History Ecology of the Sharksucker, Echeneis naucrates, in the Gulf of Mexico
Date
2015-08-19
Authors
Bachman, Beverly
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Abstract
The purpose of this investigation was to understand how symbiotic sharksucker-host interactions may have shaped life history characteristics of the symbiont. Here, I examined growth, trophic ecology, and reproduction of Sharksucker, Echeneis naucrates, in the northeastern Gulf of Mexico. Age was determined from otoliths, and growth (in standard length, SL) was modeled as a von Bertalanffy function. Males and females grew at similar rates (K = 0.54 and 0.51 year-1, respectively), but asymptotic length was significantly higher in females (L∞ = 514 mm) than males (L∞ = 445 mm). Diet varied by size group. Ectoparasitic copepods and other small crustaceans were the most frequently occurring item (78%) in the stomachs of small (<249 mm SL) sharksuckers, and fish was the second most frequent item (46%). Large sharksuckers consumed crustaceans less frequently (31%) and fish more frequently (60%). Crustaceans comprised a higher mean proportion of volume (MV) of small sharksucker diet (54% vs. 13%), and MV of fish was lower (15% vs. 32%). Sharksucker stable isotope N and C values exhibited significant trends with body size by location. Small (<249 mm SL) sharksuckers were enriched in δ13C and depleted in δ15N. Further, those from the Big Bend area were depleted in δ13C and δ15N relative to samples from the Florida Keys. Gonad histology indicated that sharksucker are indeterminate batch spawners with a peak reproductive period in the late summer in the northeast Gulf of Mexico. Gonadosomatic indices peaked for both male and female sharksuckers in August. Mean relative batch fecundities estimated from hydrated oocytes was 42.0 hydrated oocytes per gram ovaryfree body weight (OFBW). Due to unique life history adaptations, this symbiotic species appears particularly vulnerable to host availability during critical life stages. Thus, the conservation status of host species (i.e., sharks), which are in decline in many regions, is intimately tied to the population status of the sharksucker.
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Keywords
Ecology, Remora, Sharksucker, Echeneis naucrates