Open zenrabbit opened 7 years ago
tttang0602
commented
7 years ago I think this is a very good proposal and angel of studying the predator-prey dynamic of dolphins. It also aligns well with my proposal #20 which aims at study the interaction of the dolphins and their prey using mathematical models. I like the idea of introducing multiple attributes such as season, habitat, fishing operation to obtain insights of the dolphin-shrimp dynamic.
paulacetus
commented
7 years ago Hi @tttang0602. Thanks for your comment. I just dropped some comments/Qs on your proposal as I'm trying to understand the prey component you proposed. I also agree that we could combine our proposals. For e.g., a way to simplify the prey component on your project, could be to switch to shrimper effects. Even if we don't get a chance to collaborate on this "hybrid" of our projects now, I'd love to explore other opportunities.
Author: Paula Moreno Topic: Marine mammal population health
Summary
The proposed synthesis project consists of an investigation of interactions of dolphins with the Gulf shrimp fishery using the Galveston Bay (GB), Texas, as a case-study. Specifically to evaluate: (a) the prevalence of association of dolphins feeding with shrimpers throughout the year and under different environmental conditions; (b) what are the driving factors of dolphin-shrimper feeding associations; (c) whether feeding with the nets (a behavior of concern because of the risk of entanglement, while feeding on discards does not pose risk of entanglement) is the main type of feeding association. This knowledge is essential to better understand this dolphin-human interaction and inform restoration measures for dolphin populations focused on reducing incidental entanglements. In addition, it will provide a robust baseline (constructed from 4-years of intensive pre-DWH vessel surveys) of dolphin-shrimper associations in GB (reference site). Establishing this baseline allows testing for post DWH changes in GB and across various adjacent populations impacted by the DWH (e.g. If suitable dolphin habitat, including prey availability, is insufficient in DWH impacted areas, an influx of dolphins into unaffected areas such as GB, and intensified dolphin-shrimper associations, are likely to occur). These dolphin-shrimper associations are known in estuaries from Texas to Alabama, but to date have not been quantified. The data sets are readily available and suitable to manipulate, analyze and visualize using several planned workshop techniques and would lead to a publishable manuscript to support restoration efforts in the Gulf.
Data Needs
The primary data source is from systematic line-transect, vessel surveys conducted by the applicant during 4 years. Data are in Excel spreadsheets and Access databases. Each dolphin-shrimper observation includes: date; time; location (GPS coordinates); group size and composition (number of calves, juveniles, adults); dolphin behavior (feeding from discards or from the nets); seabirds (counts and species); fishing operation (trawling, hauling nets, etc.); vessel ID; habitat data (depth, water temperature, salinity). Other complementary, but not essential, data sources are the National Marine Fisheries Service (NMFS) reports (U.S. Commercial Fisheries Statistics) available online (https://www.st.nmfs.noaa.gov/commercial-fisheries/) for shrimp landings, bycatch discards, and vessel/gear characteristics to enhance the factors explored as explanatory variables.
Analytical Approaches
Potential approaches to develop predictive models using R: Generalized Linear Models (or GAMs) and Random Forests. The dependent variable is the number of dolphins per shrimper and the explanatory variables consist of a suite of attributes: season, time of day, habitat, group composition, behavior, fishing operation, seabirds, etc. To determine if dolphin-shrimper associations occur preferentially in certain areas and habitats, we could conduct hot-spot analysis using GIS tools from R or Python.
Impact and Significance
This project addresses the Gulf Research Program Goal 3: “Advance understanding of the Gulf of Mexico region as a dynamic system with complex, interconnecting human and environmental systems, functions, and processes to inform the protection and restoration of ecosystem services.” The linkage of interest is the foraging association of bottlenose dolphins—a protected species recognized as a sentinel of ocean health—with the shrimp fishery which is prevalent throughout the western and northern Gulf, including estuaries. Thirty-one bottlenose dolphin populations are identified in the Bays, Sounds and Estuaries (BSE) of the Gulf of Mexico. Typically, BSE stocks are small, slow growing and particularly vulnerable to human impacts, as emphasized by the long recovery time (up to 46 years) of dolphin populations to pre-DWH abundance levels. The shrimp fishery is the most valuable of the Gulf fisheries with revenue in 2014 of $588 million. A NMFS report on entanglement of bottlenose dolphins in the Gulf shrimp fishery raised concern about the potentially unsustainable bycatch rates of dolphins from inshore waters. However, NMFS cautioned that inshore estimates were extrapolated from deeper waters, where fishing gear is different. Hence, NMFS stressed the need to understand risk factors of entanglement in inshore waters. This study, by identifying the factors that drive the dolphin-shrimper association and the prevalence of high-risk behavior (feeding behind the nets) in a Gulf estuary, is an import step in this direction. Last but not least, the number of dolphins (and seabirds) that typically forage with shrimpers in estuaries is a useful metric to inform estuarine ecosystem modeling efforts. Shrimpers, dolphins and seabirds are significant apex consumers in most Gulf estuaries, thus accounting for these energetic flows is essential to understand these important ecosystems."