Research

Fish Census of Selected Artificial Reefs in Broward County

Principal Investigator: Richard Spieler, Ph.D.

Issue

diver conducting researchDerelict ships are commonly deployed as artificial reefs in the United States, mainly for recreational fishers and divers. Over 500 vessel-reefs lie in Florida waters alone. Despite their popularity, few studies have rigorously examined fish assemblages on these artificial reefs and compared them to natural reef.

Project and Findings

13- and 12-month interval graph resultsSix vessel-reefs off the coast of southeast Florida were censused quarterly (two ships per month) to characterize the associated fish assemblages. SCUBA divers used a non-destructive point-count method to visually assess the fish assemblages over 13- and 12-month intervals (March 2000 to March 2001 and March 2002 to February 2003). During the same intervals, fish assemblages at neighboring natural reefs were also censused. A total of 114,448 fishes of 193 species was counted on natural and vessel-reefs combined. Fish abundance and species richness were significantly higher on vessel-reefs in comparison to natural reef. Haemulidae (grunts), the most abundant family on vessel-reefs, represented 46% of total abundance.

On natural reefs, wrasses were the most abundant family, accounting for 24% of total abundance. The number of species also differed among vessel-reefs, with the most recently deployed having fewer species than the earliest deployed. Fish assemblage structure on natural versus artificial reefs exhibited a low similarity (27%). Interestingly, the juvenile phase of two deep-water, economically important species was repeatedly recorded on vessel-reefs, but has never been observed on natural reef in our study area. This may be an indication that vessel-reefs are supplying ancillary nursery/juvenile habitat for these animals that may be unavailable or limited on surrounding natural reef. Further, a comparison of natural reef sites immediately adjacent to the vessels with those more distant, does not support a simple aggregation hypothesis.

Implications for Management

Artificial Reefs remain important tools for resource managers. This study clearly shows that the effects of deploying vessel-reefs on the natural environment are complex and not a simple aggregation from neighboring habitat.

Additional research is currently ongoing examining the fish assemblages on deeper vessel-reefs (>50 m) and neighboring hardbottom using a remotely operated vehicle (ROV).

Partners

NCRI via NOAA-CSCOR