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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. [ABSTRACT FROM AUTHOR]

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 volitansandP. 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. [ABSTRACT FROM PUBLISHER]

Fisheries on lower trophic levels act as and compete with predators in aquatic ecosystems for potentially limited prey resources. Multiple predators in a system are often managed to achieve a B msy that could result in a total predator consumption level the ecosystem cannot support. We developed an Ecopath model for Pamlico Sound, NC and its tributaries to address this issue. The model is comprised of 43 compartments with an emphasis on piscivores and their prey and represents the 2012–13 time period. We estimated total predator demand for fish prey and identified important species of forage fish and top piscivorous predators in Pamlico Sound. We compared local fishing fleet removals and predator consumption in forage fish, penaeid shrimp, and blue crabs. Finally, we evaluated the impact of increased predator demand on the system, by increasing biomass levels of five predators to equal their management thresholds and using mixed trophic impact analysis. Atlantic menhaden (Brevoortia tyrannus), anchovy (Anchoa hepsetus and A. mitchilli), spot (Leiostomus xanthurus), and Atlantic croaker (Micropogonias undulatus) were the most important forage fish in the system, representing over 80% of the fish consumed (by weight). Lizardfish (Synodus foetens) and bottlenose dolphins (Tursiops truncates) were top predators based on trophic level, while bluefish and longnose gar (Lepisosteus osseus) were top predators in terms of total fish consumption. The highest overlap in forage fish usage exists between fisheries and piscivores for Atlantic croaker and spot. Total forage fish removals through predation and harvest was greater than 65% of the production for each of the four-forage fish and, under the higher predator biomass model, total removals exceeded production for spot; total removals in either scenario did not exceed the production of penaeid shrimp and blue crab. Thus, the tradeoff between fisheries for forage fish and piscivores should be considered when assessing and managing fisheries in Pamlico Sound. [Display omitted] • A food web model for a large lagoonal estuary was developed and validated. • Important forage included Engraulids and Clupeids but also small Sciaenids. • Forage fish removals were higher through predation than fisheries. • Forage was unable to simultaneously support top piscivores at management targets. [ABSTRACT FROM AUTHOR]