This objective of this research effort is to estimate mortality components and escapement rate of Red Drum stock in Mississippi. This project consists of determinations of instantaneous natural mortality rate, evaluation of overall and year-specific instantaneous total mortality rates, and calculation of the overall and year-specific instantaneous fishing mortality rates of Red Drum in Mississippi. Mortality estimates are then used to calculate an escapement rate. Alternative natural mortality estimations and fishery recruitment criteria are also evaluated to elucidate the impact of model misspecification and how these decisions affect the escapement rate.
Evaluation of Carbon and Nitrogen Stable Isotopes of Red Drum in the Northern Gulf of Mexico
The objective of this research effort is to evaluate the length-at-age and weight-at-length relationships of Red Drum. Sex-specific length-at-age and sex-specific weight-at-length relationships are quantified using multiple candidate models to determine the best supported model. Sex-specific relationships were examined for significant differences in male and female Red Drum.
Sex-Specific Growth and Reproductive Dynamics of Red Drum in the Northern Gulf of Mexico
The objective of this research effort is to use the Gulf of Mexico states’ monthly fishery independent data collection efforts to understand temporal and spatial dynamics of the Gulf Menhaden fishery. Length and weight data are examined for individuals collected by state agencies in Texas, Louisiana, Mississippi, and Alabama. Age of Gulf Menhaden is determined blindly using whole, polished otoliths and scale samples. This work will also be used to form recommendations for methodology improvements to enhance ageing precision.
The objectives of this research effort are to create a trophic network for the northern Gulf of Mexico using historical literature. Network analysis techniques are used to test the resilience of the trophic dynamics to perturbations. We also will use these techniques to examine how predator feeding effort may be reallocated among other prey when prey items are reduced. This work will provide and understanding of the complex trophic dynamics in the Gulf and highlight the cascading effects of perturbations in the system.
Interactive Data Visualization Tools for Enhanced Communication with Stakeholders
The objectives of this research effort are to develop a heirarchical Bayesian surplus production model in the northern Gulf of Mexico to assist with stock assessments of Blue Crab. Currently, inshore Blue Crab are assessed and managed at a state level, however, there is evidence that there is only one stock. This model model uses indices of abundance and catch data from different basins or states across the Gulf to estimate a total abundance of Blue Crab in the northern Gulf of Mexico. The heirarchical Bayesian framework is flexible, allows easy incorporation of multiple data sets, and allows for the direct estimation of missing data or errors. The sensitivity of the analysis is tested to the exclusion of each index of abundance.
The objective of this research effort is to describe age and growth characteristics of Atlantic Chub Mackerel from the coastal Mid-Atlantic and New England region of the United States. Age estimates from both whole and sectioned otoliths are evaluated to determine which method results in highest precision. Otolith-derived age estimates are then used to evaluate the length-at-age relationship using a suite of non-linear growth models. The weight-at-length relationship is modeled using a power function. Median growth parameter estimates of Atlantic Chub Mackerel from the northwest Atlantic are compared with mean parameter estimates reported from other regions in the Atlantic and Mediterranean.
Age and growth of Atlantic chub mackerel (Scomber colias) in the Northwest Atlantic
The objective of this research effort is to describe elements of the reproductive biology of Atlantic Chub Mackerel in the northwest Atlantic. Histological techniques are used to determine sex and length- and age-specific sexual maturity. The approximate spawning season is identified using histological indicators and evidence of spawning from analysis of historical data on larval fish collections and commercial catch. These data will be used to inform the effective management of Atlantic Chub Mackerel stock.
The objective of this research effort is to use a simulation-based analysis to evaluate the efficacy of stock enhancement for Spotted Seatrout in the north-central Gulf of Mexico. An operating model is developed to represent the biological characteristics of the stocks and attributes of the associated recreational fisheries. The results from this work will provide insight into the magnitude of effort needed to enhance Spotted Seatrout stocks and the associated costs.
The objectives of this research effort are to develop a management strategy evaluation for Vermilion Snapper in the northern Gulf of Mexico. A suite of operating models will be used to represent the true underlying population dynamics of the stock and the major uncertainties associated with that stock, such as stock-recruit relationship. The operating models will be used to test a set of proposed management strategies and performance statistics will be used to evaluate how well or poorly the stock responded to each strategy. This methodology can be used to evaluate trade-offs of different management regulations and how variable the outcome may be prior to implementing any regulations. It will provide a tool for informing future management and identifying areas where more research effort and improved data would enhance assessment efforts.
The effort initiated at the April, 2019 Crab Task Force at the Biennial Gulf States Marine Fisheries commission meeting identified:
The general desire of the panel members to explore the utility of alternative assessment models.
Understand the strengths and weaknesses of alternative assessment models to address the needs of individual states.
Consider that each states’ regulatory and management priorities superseded the desire for another gulf-wide assessment. There was a stated reservation by some state agency representatives that a gulf-wide assessment effort would hinder their efforts to manage their state’s resources.
Given the desire to explore models that could be used by the states and conscious that a full assessment effort was not desired, Vanderkooy (Steve Vanderkooy, GSMFC) and Leaf (Robert Leaf, University of Southern Mississippi) derived a set of terms of reference that could be accomplished. Vanderkooy’s role was to organize and coordinate the effort and Leaf’s role was to synthesize the states data, derive indices and time series where appropriate, guide the development of the modeling approach with state agency representatives, and provide a summary document.
The terms of reference for the 2019 Blue Crab Assessment Effort are provided at the end of the document.
The primary deliverables of the work: 1) Created a catalog of the Commercial, Recreational, and Fishery Independent data that could be used in a quantitative assessment. Additionally socio-economic data, and other data describing the state of the stock and fishery for inclusion into the model.
Evaluated alternative models and concluded that a traffic light model would best serve the needs of the Gulf State’s resource management agencies.
Conducted a preliminary modeling exercise using the traffic light. Participants with experience using this model from North Carolina’s state resource agency were critical in this effort.
Developed:
An online modeling platform for use by the states to understand what data sources, at what spatial scales, are most informative for their needs. The modeling framework can be found in the link below.
An input data template such that the modeling platform can be used in the future.
This report summarizes the proceeding from the October 15 Blue Crab workshop convened by GSMFC, specifically the work performed by contractor Robert Leaf to address the terms of reference outlined in the “Gulf of Mexico Blue Crab Population Modeling” effort. Following the previous workshop, the state representatives decided that the “Traffic Light Model” was the preferred assessment approach. The scope of work for Leaf was limited to evaluation and conducting preliminary analysis of the candidate models, in partnership with the state management agency representatives.
The model imports a .csv file “template” that can be found here
To understand the feasiblity of performing large-scale tag-recapture in the Gulf of Mexico. To understand the challenges we distributed this survey to scientists and those knowledgable in Red Snapper ecology:
Thanks very much for taking part in this effort to understand the ecology of Red Snapper. We are interested in how these dynamics impact our ability to determine the abundance of the stock in the nothern Gulf of Mexico. Below are a series of questions that when answered will allow us to better model population and individual dynamics of Red Snapper.
We are modeling the movement dynamics of snapper with a spatial network and seek to understand how frequently and under what circumstances fish will move to another habitat (displace), habitat characteristics, and tagging and recapture dynamics
In each of the fields below will be a series of sliders and buttons. Please interact with these to give your best estimates to the queries, based on your knowledge of Red Snapper. We understand that some of the queries may be difficult and indeed not known by the scientific community. We will be simulating the dynamics over a range of scenarios to capture this ambiguity - your thoughtful efforts will help us to understand the extent of current scientific knowledge and also understand areas where more research is needed.
Associated with many of the queries will be a field where you report the amount of confidence you have in your estimate - these will be used as criteria to partially weight your response to those of your peers. At the end of the page will be a download button so that your answers can be submitted to our team.
This application was developed for the work of Oshima and Leaf 2018. We collected diet studies from the northern Gulf of Mexico and conducted network and simulation analyses to evaluate the structure and robustness of the trophic dynamics. This app allows the user to select either a predator or prey, the diet metric used to report the interactions and the taxonomic level the nodes are shown at. Note that prey were identified to varrying taxonomic levels depending on the studies. If you do not see a network displayed or get an error, try selecting a different diet metric. The diet metrics reported for a selected predator or prey can be seen in the data table.