The across-shelf distribution of larval, postlarval and juvenile fishes collected at oil and gas platforms and a coastal jetty off Louisiana west of the Mississippi River Delta.

摘要

A cross-shelf transect of three petroleum platforms and a coastal rock jetty (another hard-substrate, artificial habitat) in the northcentral Gulf were sampled to examine the role that oil and gas platforms (hard substrate habitat) may play in the early life history stages of reef-dependent and reef-associated fishes. The ichthyoplankton and juvenile fish assemblages were sampled at Green Canyon 18 (GC 18; 230 m depth, shelf slope); Grand Isle 94 (GI 94; 60 m depth, mid-shelf); and South Timbalier 54 (ST 54; 20 m depth, inner shelf) with passive plankton nets and light-traps and at a coastal rock jetty (Belle Pass; 3–5 m depth) with a light-trap and a plankton pushnet. At all sites clupeiforms dominated samples, comprising 59–97% of the total catch. Results of Kolmogorov-Smirnov length-frequency comparisons of fish collected in plankton nets vs. light-traps (platforms) indicated light-traps generally collected significantly larger individuals. At the jetties, greater overlap in size distributions was observed for comparisons of the pushnet and light-trap. Reef-dependent (e.g., pomacentrids, scarids, chaetodontids and labrids) and reef-associated (e.g., serranids, lutjanids, blenniids and holocentrids) taxa were relatively rare in our collections compared to coastal pelagic (scombrids and carangids) and demersal taxa (sciaenids), which are also often associated with petroleum platforms. Taxonomic richness and diversity was highest at mid-shelf platform (GI 94), possibly a result of its proximity to a high density of upstream and surrounding platforms which may create generally favorable conditions for the recruitment of reef taxa. Preflexion and early larval stages of reef-dependent and reef-associated fishes were collected at the outer shelf platform (blenniids, holocentrids, serranids, lutjanids and scarids), mid-shelf platform (pomacentrids, blenniids, holocentrids, lutjanids and serranids), and inner shelf platform (blenniids and lutjanids), suggesting nearby spawning or local supply. Similarly, presettlement and settlement-sized reef-dependent and reef-associated fishes were collected at the outer shelf (pomacentrids, scarids, blenniids, serranids, lutjanids and holocentrids), midshelf (pomacentrids, blenniids, serranids, lutjanids and holocentrids), and inner shelf (labrids, blenniids, serranids and lutjanids) platforms. With the limited amount of hard-substrate habitat available in the northern Gulf, the addition of artificial habitats (platforms) may increase the chances of finding suitable spawning or settlement habitat.