Detecting Population Regulation of Winter Flounder from Noisy Data

Year-class size of marine fish is thought to be determined during the first year of life, with density-dependent mortality during the larval or juvenile stages. However, investigations of such dynamics are often limited by data availability. To test this paradigm for winter flounder (Pseudopleuronectes americanus) in Narragansett Bay, Rhode Island, the abundances of 29 year classes moving through seven life stages were analyzed with a novel extension of key-factor analysis. Evidence of density dependence was identified between the egg and July young-of-the-year stages and high process-error variance was detected throughout the life cycle, suggesting year-class size is not fully determined until age-2. However, the first summer appeared to be a critical life stage for winter flounder, during which high temperatures, hypoxia, and predator abundance contributed to increased mortality rates behind a long-term population decline. Due to its general data requirements, the key-factor analysis method developed here may be applied to other marine populations to identify the impacts of external stressors at particular life stages and the degree to which they are compensated by density-dependent processes.

Investigating Potential Applications of the Fish Anti-Microbial Peptide Pleurocidin: A Systematic Review

The anti-microbial peptide (AMP) pleurocidin is found in winter flounder (Pseudopleuronectes americanus), an Atlantic flounder species. There is promising evidence for clinical, aquaculture, and veterinary applications of pleurocidin. This review provides an overview of the current literature available on pleurocidin to guide future research directions. By fully elucidating pleurocidin’s mechanism of action and developing novel treatments against pathogenic microbes, populations of flatfish and humans can be protected. This review consulted publications from PubMed and Environment Complete with search terms such as “pleurocidin”, “winter flounder”, and “antimicrobial”. The fish immune system includes AMPs as a component of the innate immune system. Pleurocidin, one of these AMPs, has been found to be effective against various Gram-positive and Gram-negative bacteria. More investigations are required to determine pleurocidin’s suitability as a treatment against antibiotic-resistant pathogens. There is promising evidence for pleurocidin as a novel anti-cancer therapy. The peptide has been found to display potent anti-cancer effects against human cancer cells. Research efforts focused on pleurocidin may result in novel treatment strategies against antibiotic-resistant bacteria and cancer. More research is required to determine if the peptide is a suitable candidate to be developed into a novel anti-microbial treatment. Some of the microbes susceptible to the peptide are also pathogens of fish, suggesting its suitability as a therapeutic treatment for fish species.

Composition and Intraspecific Variability in Summer Flounder (Paralichthys dentatus) Diets in a Eutrophic Estuary

This study assessed the diet of Summer flounder (SF, Paralichthys dentatus) in Shinnecock Bay, NY. Summer flounder are a recreationally and commercially important marine flatfish species found along the Eastern United States coastline. Despite their importance, few studies have examined the trophodynamics of a broad size spectrum of this species. Diet composition of summer flounder (n = 88) was assessed from 2014 to 2016 throughout Shinnecock Bay, a eutrophic bar-built estuary in New York. Species consumed and diet species richness differed significantly amongst SF size classes, with large [≥375 mm total length (TL)] and medium (>225: <375 mm) summer flounder showing higher levels of piscivory and more diverse diets than small-sized (≤225 mm) conspecifics. As voracious plastic predators, trends in annual and monthly diet variation generally followed prey availability in Shinnecock Bay. One exception to this general pattern occurred for winter flounder (Pseudopleuronectes americanus). Despite their low relative abundance in the bay, winter flounder was highly preferred as prey by summer flounder (Chesson index, α = 0.35) and was their predominant prey item accounting for 12.3% (SD ± 3.9%) of the diet by weight. Other factors that explained the variability of the diet of summer flounder were year, month, dissolved oxygen concentration, bay region and habitat, with a cumulative variance of 10.3%. Interestingly, clear differences in the diet (i.e., species richness and abundance) of summer flounder were found within regions of Shinnecock Bay, with a decrease in teleost biomass and species richness observed in the western region where water quality is more degraded and less seagrass is available compared to the more pristine eastern region. Distinct trophic dynamics in degraded habitats suggests fundamentally different food webs that could have important consequences to ecosystem stability and resilience. As coastal areas continue to experience degradation, diet studies of economically and ecologically important species can aid in the development of effective ecosystem-based management plans.