THE CONTRIBUTIONS OF HABITAT STRUCTURE AND LARVAL SUPPLY TO BROAD-SCALE RECRUITMENT VARIABILITY IN A TEMPERATE ZONE, SEAGRASS-ASSOCIATED FISH

The contribution of habitat structure and larval supply to broad-scale spatial variability in recruitment of a temperate zone, seagrass asso ciated fish, Sillaginodes punctata (Cuvier and Valenciennes), was inve stigated in Port Phillip Bay, Australia, from September to November, 1 994. Replicate artificial seagrass beds were placed at five sites over a 50 km section of coastline, and artificial and adjacent natural sea grass were sampled approximately fortnightly for Sillaginodes punctata recruitment. Significant differences in recruitment amongst sites wer e apparent for both natural and artificial seagrass. A small but signi ficant effect of habitat was detected where more recruits occurred in artificial relative to natural seagrass at sites with longer plant ste ms in the natural seagrass. The contribution of larval supply to spati al variability in recruitment was investigated by sampling natural sea grass, and concomitantly sampling the plankton immediately offshore fo r pre-settlement larvae. There was no significant correlation between larval abundances and recruitment, or between habitat structure and re cruitment, over nine sites. We hypothesise that the high spatial varia bility in recruitment;attributable to location is probably related to a combination of factors. These factors may include variation in larva l supply, and also variation in the physical exposure of the location that influences mortality and movement of recruits in the early post-s ettlement stage. (C) 1998 Elsevier Science BN.