Feeding ecology of four hatchetfishes (Sternoptychidae) in the eastern Gulf of Mexico
Abstract:Vertical distribution and trophic ecology of hatchetfishes were investigated in the eastern Gulf of Mexico. The four principal species, Argyropelecus aculeatus, A. hemigymnus, Sternoptyx diaphana and S. pseudobscura, ranged in abundance from 21–53 × 103 km−2 in the upper 1,000 m. There is strong evidence for time-space and food resource partitioning among these species. Depth of habitat and diet characteristics are reflected in cryptic adaptations and functional morphology of the two genera.
A. aculeatus appeared to feed in the epipelagic zone (<200 m) early at night. Ostracods and copepods were the most important (biomass) food for smaller size classes, and pteropods, euphausiids and fish for larger individuals. A. hemigymnus apparently foraged in late afternoon in the 300–500-m zone. Ostracods and copepods were the principal food of all size classes. Cyclic feeding was not evident in either species of Sternoptyx. S. diaphana, which occurred primarily at 500–800 m, fed largely on copepods, ostracods and amphipods as juveniles and on amphipods and euphausiids at maturer sizes. S. pseudobscura which occurred mostly below 800 m, ingested primarily copepods, polychaetes and euphausiids as juveniles and took proportionately more amphipods and fish as adults.
Non-random food choice was apparent, the Argyropelecus species selectively feeding on ostracods and S. diaphana on ostracods and amphipods. Much of the food of S. pseudobscura, inexplicably, was epipelagic in origin. Diet, depth and morphological characteristics of these hatchetfish species support the case for reduction of intraspecific competition through evolution.
Document Type: Research Article
Publication date: March 1, 1985
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