Exploited Species Impacts on Trophic Linkages Along Reef–seagrass Interfaces in the Florida Keys

Abstract

The removal of fish biomass by extensive commercial and recreational fishing has been hypothesized to drastically alter the strength of trophic linkages among adjacent habitats. We evaluated the effects of removing predatory fishes on trophic transfers between coral reefs and adjacent seagrass meadows by comparing fish community structure, grazing intensity, and invertebrate predation potential in predator-rich no-take sites and nearby predator-poor fished sites in the Florida Keys (USA). Exploited fishes were more abundant at the no-take sites than at the fished sites. Most of the exploited fishes were either omnivores or invertivores. More piscivores were recorded at no-take sites, but most (approximately 95%) were moderately fished and unexploited species (barracuda and bar jacks, respectively). Impacts of these consumers on lower trophic levels were modest. Herbivorous and smaller prey fish (< 10 cm total length) densities and seagrass grazing diminished with distance from reefs and were not negatively impacted by the elevated densities of exploited fishes at no-take sites. Predation by reef fishes on most tethered invertebrates was high, but exploited species impacts varied with prey type. The results of the study show that, even though abundances of reef-associated fishes have been reduced at fished sites, there is little evidence that this has produced cascading trophic effects or interrupted cross-habitat energy exchanges between coral reefs and seagrasses.

Spatial Patterns in Herbivory on a Coral Reef Are Influenced by Structural Complexity but Not by Algal Traits

“…The distinct spatial patterns in consumption of algae described in this study are also similar to the GBR [30], [33], as well as to reefs found in the Caribbean [29], [35], [49], and in the Hawaiian Islands [50]. Herbivory is always highest in coral-dominated habitats near or at the reef crest, and decreases with either depth or distance towards the inner sections of lagoons.…”

Depletion of predatory fish by fishing in a ­temperate reef ecosystem leads to indirect effects on prey, but not to lower trophic levels

“…(11-55 mm), perhaps even small individuals are too large for the main predators, as observed for the trochid gastropod Tectus pyramis (Scheibling & Hatcher 1997). Other studies have also found low predation rates on gastropods (McClanahan 1992, Valentine et al 2008, and thick-shelled gastropods might be well protected from most predators. Indeed, predation rates can vary substantially between gastropods with different shell thicknesses (Tuya et al 2010).…”

Climate Change Impacts on Marine Ecosystems

“…For example, Gulf menhaden transported 5%-10% of primary production of estuaries in Louisiana to deeper communities in the Gulf of Mexico (Deegan 1993). Energy exchanges between habitats such as mangroves-coral reefs and coral reefs-seagrasses can be disrupted in complex ways as fish abundances decline (e.g., Mumby & Hastings 2008, Valentine et al 2008). Many studies have found that altering the metapopulation dynamics of a species can reduce its ability to withstand pressures because rescue and recolonization dynamics are disrupted (e.g., Lipcius et al 2008).…”