David B. McClellan

Recent Region-wide Declines in Caribbean Reef Fish Abundance

Profound ecological changes are occurring on coral reefs throughout the tropics, with marked coral cover losses and concomitant algal increases, particularly in the Caribbean region. Historical declines in the abundance of large Caribbean reef fishes likely reflect centuries of overexploitation. However, effects of drastic recent degradation of reef habitats on reef fish assemblages have yet to be established. By using meta-analysis, we analyzed time series of reef fish density obtained from 48 studies that include 318 reefs across the Caribbean and span the time period 1955-2007. Our analyses show that overall reef fish density has been declining significantly for more than a decade, at rates that are consistent across all subregions of the Caribbean basin (2.7% to 6.0% loss per year) and in three of six trophic groups. Changes in fish density over the past half-century are modest relative to concurrent changes in benthic cover on Caribbean reefs. However, the recent significant decline in overall fish abundance and its consistency across several trophic groups and among both fished and nonfished species indicate that Caribbean fishes have begun to respond negatively to habitat degradation.

Influence of marine reserve size and boundary length on the initial response of exploited reef fishes in the Florida Keys National Marine Sanctuary, USA

We examine the influence of reserve size and boundary length on the relative rate of fish density change in reserves versus fished reference reefs for three exploitable-sized reef fish categories: (1) combined fish (34 species of Haemulidae, Lutjanidae, Serranidae, and hogfish Lachnolaimus maximus); (2) Haemulidae (13 species); and (3) Lutjanidae (9 species). If reef habitat boundaries are highly permeable to fish movements then fish recovery within a reserve would be inversely proportional to: reserve perimeter (RP)/total reserve area (RA) (RP/RA). If, however, reef habitat boundaries are relatively impermeable barriers to fish movements, recovery within the reserve would be inversely proportional to: reserve boundary that intersects reef habitat (HI)/reef habitat area within the reserve (HA) (HI/HA). From 1994 to 2001 we monitored reef fishes within and outside of no-take marine reserves established in 1997 in the Florida Keys, USA. A significant majority of reserves had greater rates of density change than reference reefs for Lutjanidae and combined fish (22 of 24 reserves for both categories). Significantly higher rates of density change were found in ten reserves for Lutjanidae, two reserves for combined fish, and one reserve for Haemulidae. Reserves appeared to promote an increased density of exploitable fishes. A significant, negative, but weakly correlated relationship was found between the relative rate of density change (RDC) for combined fish and the HI/HA ratio. Reserve size and placement appeared to have a minimal effect upon RDC.

A major developmental defect observed in several Biscayne Bay, Florida, fish species

SynopsisStunted or missing dorsal spines or rays, sometimes accompanied by a depression in the dorsal profile, were found in 10 fish species in six families from North Biscayne Bay. The same morphological abnormality occurred inHaemulon sciurus, H. parrai, H. plumieri, Lagodon rhomboides, Archosargus rhomboidalis, Diplodus argenteus, Lutjanus griseus, Kyphosus sectatrix, Sphoeroides testudineus, andLactrophyrys quadricornis. Another morphological abnormality, scale disorientation, was found in six species:H. parrai, L. rhomboides, A. rhomboidalis, L. griseus, andAbudefduf saxatilis. Pugheadedness, jaw deformities, and other abnormalities also were observed. The occurrence of similar deformities across such a spectrum of fishes from the same location suggests the deformity was induced by something in the environment common to all these species. Although there could be other explanations for the unusual cluster of abnormalities, it is suspected that the same environmental contaminant or group of contaminants is adversely affecting a common developmental pathway of these fishes. Biscayne Bay is an urban estuary that receives agricultural, industrial, and residential run off.

Apparent rapid fisheries escalation at a remote Caribbean island

Navassa Island is a small uninhabited island, approximately 60 km west of the south-west tip of Haiti (18°24′N, 75°00′W). Haiti laid claim to the island in 1804, however the USA claimed it under the Guano Act of 1856 and recently placed it under jurisdiction of the US Fish and Wildlife Service (USFWS). Remoteness from USFWS administration in Puerto Rico and disputed sovereignty by Haiti make enforcement of management impractical. Artisanal fishers from Haiti have frequented Navassa over the past several decades. Given the lack of current land-based development and limited transient land-based activity (for example salting fish and gear construction), Navassa provides a case study where fishing is largely isolated as the dominant human impact on coastal resources.

An Extensive Deep Reef Terrace on the Tortugas Bank, Florida Keys National Marine Sanctuary

While most of the mapped area (137.5 km 2 ) of the Tortugas Bank consists of low-relief hard-bottom (105.5 km 2 or 77%) and scattered, rocky outcrops (16.6 km 2 or 12%), a sizeable portion of the western rim or platform edge (24 o 42.30’ N, 83 o 02.64’ W) is a well-developed reef terrace community (top panel). The topography of the substratum is very complex, owing to the numerous undercuts and caverns, as well as mushroom-shaped and plating corals up to 2 m in height. Coral cover is high (26.3 to 28.3% among three sites visited) relative to offshore reefs in the Florida Keys and is dominated by Montastraea faveolata, M. franksi, M. cavernosa, and Siderastrea siderea. The terrace community is a deeper version (22-27 m) of the reef terraces near Loggerhead Key 15 km to the southeast in Dry Tortugas National Park (Davis 1982). Anecdotal observations suggested that the western edge of the Tortugas Bank, locally named Sherwood Forest because of the predominance of mushroom-shaped corals (bottom panel), was spatially extensive. Using a combination of side-scan sonar, diver surveys, and bathymetry data, we estimate that the reef terrace is approximately 15 km 2 or about 10% of the mapped area of the Tortugas Bank. The “discovery” of this area by our science team was clearly preceded by the knowledgeable and active fishers of the region. Despite the remoteness of the Dry Tortugas relative to the Florida Keys, and the well developed reef structure, preliminary data indicate evidence of overfishing by a general absence of large species and individuals among exploited species, especially grouper (Serranidae) and snapper (Lutjanidae). Also, surprisingly few shark and barracuda were observed, and there was evidence of shrimp trawl damage to hard-bottom habitat. Because remoteness does not guarantee protection, the implementation of marine reserves in this region holds promise for restoration of fish stocks and protection of one of the largest areas of well-developed and previously undescribed coral reefs in Florida.

Transport and connectivity modeling of larval permit from an observed spawning aggregation in the Dry Tortugas, Florida

Large aggregations of adult permit (Trachinotus falcatus) were consistently observed since 2004 by divers in a collaborative fishery-independent reef fish visual census survey during May and June on the western-most edge of the Dry Tortugas Bank, Florida, in coral reef habitat, indicating proximal spawning sites. We investigated the possible fate and connectivity of larvae spawned at this location in the Dry Tortugas and two other published aggregation sites through a drift analysis using the ocean circulation and transport dynamics simulator HYCOM (Hybrid Community Ocean Model). New age-length data facilitated the determination of larval durations and rates of juvenile growth. Modeled larval transport data from spawning sites in the Dry Tortugas, Belize and Cuba were evaluated and compared to a spatially-extensive empirical juvenile permit data set from Florida. Our study revealed that unique oceanographic processes provided pathways for both downstream larval transport and juvenile retention, to and from Florida waters. These simulation results indicated that the Dry Tortugas region is a key source of permit recruits to southeast Florida stretching from the Florida Keys and up Florida’s east coast, and to a much lesser extent the west Florida shelf. Simulations from Belize and Cuba spawning sites revealed high local retention with low connectivity to Florida, emphasizing the importance of local resource management throughout the permit’s range.