G. Todd Kellison

Invasive lionfish reduce native fish abundance on a regional scale

Invasive lionfish pose an unprecedented threat to biodiversity and fisheries throughout Atlantic waters off of the southeastern United States, the Caribbean, and the Gulf of Mexico. Here, we employ a spatially replicated Before-After-Control-Impact analysis with temporal pairing to quantify for the first time the impact of the lionfish invasion on native fish abundance across a broad regional scale and over the entire duration of the lionfish invasion (1990–2014). Our results suggest that 1) lionfish-impacted areas off of the southeastern United States are most prevalent off-shore near the continental shelf-break but are also common near-shore and 2) in impacted areas, lionfish have reduced tomtate (a native forage fish) abundance by 45% since the invasion began. Tomtate served as a model native fish species in our analysis, and as such, it is likely that the lionfish invasion has had similar impacts on other species, some of which may be of economic importance. Barring the development of a control strategy that reverses the lionfish invasion, the abundance of lionfish in the Atlantic, Caribbean, and Gulf of Mexico will likely remain at or above current levels. Consequently, the effect of lionfish on native fish abundance will likely continue for the foreseeable future.

Pilot Evaluation of Early Juvenile Blue Crab Stock Enhancement Using a Replicated BACI Design

We quantified whether local populations of early juvenile blue crabs (J1–2) could be enhanced through the translocation of crabs to underutilized nursery habitats, and if enhancement success, survival, and potential impacts of stocked crabs on their benthic prey varied in a density-dependent manner. Using plankton nets, ∼143,000 blue crab megalopae were collected as they ingressed into Pamlico Sound, NC. Of these, ∼13,800 early juvenile blue crabs (J1–2 stages) were then stocked at potential nursery sites relatively far removed (32–70 km) from their initial settlement areas using a replicated before-after control impact (BACI) experimental design. On average, there was negative enhancement success (−34%) five weeks after local crab enhancement, and no evidence of density-dependent enhancement success, mortality, or impact on potential crab prey. Poor stocking success was likely due to pelagic emigration from enhancement sites relative to controls. Attempts to assess the feasibility of stocking blue crabs at local scales of small coves should (i) probably not consider J1–2 stages because of their apparent propensity to emigrate from these areas, or (ii) further assess the effects of geomorphology and wind fetch of release sites on density-dependent emigration.

Geomorphic Characterization of Reef Fish Aggregation Sites in the Upper Florida Keys, USA, Using Single-Beam Acoustics

The objective of this study was to determine if multiple reef fish aggregation sites in the upper Florida Keys share characteristic geomorphic features. A commercial single-beam acoustic seabed classification system was used to map the seabed in the vicinity of reported or observed black grouper (Mycteroperca bonaci), mutton snapper (Lutjanus analis), and yellowtail snapper (L. chrysurus) aggregation sites. Results showed that drowned, margin-parallel, rocky ridges, known locally as outlier reefs, were features found in proximity to all of the mapped aggregation sites. In particular, three geomorphic characteristics were observed at most sites: a steep slope of the landward boundary of the upper slope terrace, an exposed outlier reef forming the seaward boundary of the upper slope terrace, and at least one other exposed outlier reef on the upper slope terrace. The results suggest that the acoustic-mapping technologies used herein could be valuable when considering the placement of marine reserves.