Mark J. Wuenschel

Estimating the Energy Density of Fish: The Importance of Ontogeny

Abstract Ontogenetic patterns in the percent dry weight (%DW) and energy density (joules per gram of wet weight) were studied in the early life stages of the subtropical estuarine and marine gray snapper Lutjanus griseus and the warm-temperate estuarine and marine spotted seatrout Cynoscion nebulosus. The %DW was variable for individuals of both species but increased significantly through larval to juvenile stages ( 50 mm). The lipid percentage, which was determined only for gray snapper, was also variable between individuals but showed significant increase with body size. Strong relationships between percent dry weight and energy density were evident for both species; however, the slopes of regressions were significantly lower than in general multispecies models, demonstrating the need for species- and stage-specific energy density data in bioenergetics models.

Projecting Range Limits with Coupled Thermal Tolerance - Climate Change Models: An Example Based on Gray Snapper (Lutjanus griseus) along the U.S. East Coast

We couple a species range limit hypothesis with the output of an ensemble of general circulation models to project the poleward range limit of gray snapper. Using laboratory-derived thermal limits and statistical downscaling from IPCC AR4 general circulation models, we project that gray snapper will shift northwards; the magnitude of this shift is dependent on the magnitude of climate change. We also evaluate the uncertainty in our projection and find that statistical uncertainty associated with the experimentally-derived thermal limits is the largest contributor (∼ 65%) to overall quantified uncertainty. This finding argues for more experimental work aimed at understanding and parameterizing the effects of climate change and variability on marine species.

Recruitment Patterns and Habitat Use of Young-of-the-Year Bluefish along the United States East Coast: Insights from Coordinated Coastwide Sampling

Protracted spawning and pulsed juvenile production are common in coastal spawning fishes, the phenology of which determines potential environmental effects on recruitment. This article examines bluefish (Pomatomus saltatrix), a cosmopolitan coastal spawning species that produces multiple cohorts of juveniles utilizing both estuarine and coastal habitats as nurseries along the U.S. east coast. To determine recruitment on a coastwide basis, ocean (bottom, neuston, and surfzone) and estuarine habitats were sampled in Florida and North Carolina south of Cape Hatteras in the South Atlantic Bight, and Maryland, New Jersey, and New York in the Middle Atlantic Bight. This coordinated sampling effort across multiple habitats with multiple gears on a coastwide basis allowed the resolution of the occurrence, growth, and movement of cohorts along the coast. Production of the spring-spawned cohort occurred in both South Atlantic Bight and Middle Atlantic Bight habitats, while summer-spawned cohort production was limited to the Middle Atlantic Bight. Information from the present study is synthesized with prior research to develop a conceptual model of the seasonal patterns of YOY bluefish habitat use and to emphasize the value of coordinated sampling at a large spatial scale in understanding recruitment processes in this and potentially other important marine species.

Do surf zones in New Jersey provide "nursery" habitat for southern fishes?

The fishes of the energetic surf zone of exposed ocean beaches are poorly known, especially along the U.S. east coast. We investigated the role that surf zones in southern New Jersey have as habitat by describing the young-of-the-year fishes caught by seines within the surf zone from May through October in 1998, 1999, 2005 and 2006. In addition, we investigated the nursery role of these surf zones by examining abundance, growth, and inferred survival during the summer for the dominant locally (New Jersey) and southern (south of Cape Hatteras) spawned species. At least three southern species, i.e. bluefish Pomatomus saltatrix (Cohort I), white mullet Mugil curema, and Florida pompano Trachinotus carolinus successfully use New Jersey surf zones as nurseries during the summer. It is clear that bluefish (Cohort I) contributes to the adult population and it is likely for the other southern species. Ultimately, the nursery contribution of surf zones and other habitats at the northern limits of the range of southern species depends on whether surviving juveniles can successfully emigrate to overwinter habitats and complete their life history.