Species invasions in marine ecosystems pose a threat to native fish communities and can disrupt the food webs that support valuable commercial and recreational fisheries. In the Gulf of Mexico, densities of invasive Indo‐Pacific Lionfish, Pterois volitans and P. miles, are among the highest in their invaded range. In a workshop setting held over a 2‐week period, we adapted an existing trophic dynamic model of the West Florida Shelf, located in the eastern Gulf of Mexico, to simulate the lionfish (both species) invasion and community effects over a range of harvest scenarios for both lionfish and native predators. Our results suggest small increases in lionfish harvest can reduce peak biomass by up to 25% and also that reduced harvest of native reef fish predators can lead to lower lionfish densities. This model can help managers identify target harvest and benefits of a lionfish fishery and inform the assessment and management of valuable reef fish fisheries.

We present a novel spatially explicit kernel density approach to estimate the proportional contribution of a prey to a predator’s diet by mass. First, we compared the spatial estimator to a traditional cluster-based approach using a Monte Carlo simulation study. Next, we compared the diet composition of three predators from Pamlico Sound, North Carolina, to evaluate how ignoring spatial correlation affects diet estimates. The spatial estimator had lower mean squared error values compared with the traditional cluster-based estimator for all Monte Carlo simulations. Incorporating spatial correlation when estimating the predator’s diet resulted in a consistent increase in precision across multiple levels of spatial correlation. Bias was often similar between the two estimators; however, when it differed it mostly favored the spatial estimator. The two estimators produced different estimates of proportional contribution of prey to the diets of the three field-collected predator species, especially when spatial correlation was strong and prey were consumed in patchy areas. Our simulation and empirical data provide strong evidence that data on food habits should be modeled using spatial approaches and not treated as spatially independent.

No abstract

Food habits in Pamlico Sound, North Carolina, are poorly described despite the estuary's large size and importance as nursery and fisheries habitat. We conducted the first multi‐year, multispecies food habits study in Pamlico Sound, sampling the stomach contents of 16,913 predators representing 25 species. Predators were sampled from fisheries‐independent trawl and gill‐net surveys. We used multivariate analyses to compare diets between surveys, used agglomerative hierarchical cluster analyses and similarity profiles to identify significant trophic guilds, and identified forage fish using multiple approaches (qualitative classification criteria, connectance, and supportive role to fishery ecosystems [SURF]). The diets of predators sampled from the trawl survey were significantly different than predators sampled from the gill‐net survey. Mysids and anchovies were more important for trawl‐caught predators, with the majority of those predators belonging to nonpiscivorous guilds. Half of the gill‐net survey predators were piscivorous and relied more heavily on Atlantic Menhaden Brevoortia tyrannus and sciaenids. Differences in the level of piscivory between the surveys are most likely a result of larger predators being sampled in gill nets relative to trawls. There was little agreement among approaches in forage species identification, and only anchovies in the trawl survey were identified as a forage species using all approaches. Quantitative metrics identified forage species (e.g., Spot Leiostomus xanthurus and invertebrates) that were not identified by qualitative classification criteria. Our work shows the effect of gear size selection on estimates of predator diets and the need to use a variety of gears that sample a wide range of predator sizes. Additionally, the identification of forage species requires an evaluation of criteria outside of life history characteristics and a greater emphasis on the contribution of a prey species to a predator's diet.