Improving Data Inputs to Stock Assessments: a Case Study in the Reproduction of Sandbar Sharks

During stock assessments, scientists strive to use the best available science to inform decisions, while the stakeholders participate in each level of the process to be sure to make their interests known and to better understand the final outcome.  Such an integrative process requires a certain level of participation and transparency by all parties.  When a stock is determined to be overfished, the stakes become very high.  Everything is second guessed and brought into question: the model, the data, and the process itself.  The 2007 assessment of the sandbar shark (Carcharhinus plumbeus) in the Gulf of Mexico and US south Atlantic is a prime example.  After the assessment, there was a question as to the quality of the data used from the fishery and the observer program.  In 2008, a research fishery was instituted to improve catch and biological data quality.  Both age and growth and reproduction studies were carried out using research fishery data, and their results were applied to the 2011 assessment.  In spite of the improved data, the most current sandbar stock assessment still had issues of contention.  One such controversy, the reproductive periodicity, was vehemently debated throughout the process.  Due to the conflict around this life history parameter, we examined the effect of the periodicity of the reproductive cycle on the outcome of the stock assessment.  The results of this study will help to inform researchers’ decisions when confronted with conflicting or unclear results, and will help to diminish the ‘black box’ reputation some stock assessment models may have.