Hooked! An Analysis of Sea Turtle Bycatch in the Recreational Rod and Reel Pier Fishery of North Carolina
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2024-04-26
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Abstract
Fisheries bycatch is a major threat to the five species of endangered and threatened sea turtles found in North Carolina’s waters. There are four main outcomes of a bycatch event:acute death, sub-acute death, delayed mortality, or survival. Survival may be accompanied by sub-lethal impacts affecting general fitness of the sea turtle, potentially decreasing reproductive success, the turtle’s ability to forage, and increasing the risk to threats (e.g., boat strike). Post Interaction Mortality (PIM) after interaction with hook and line gear is influenced by hook-type, the ease of removing the hook from the turtle, if hooks (or line) couldn't be removed, and a myriad of environmental factors. While the commercial fishery has measures in place to decrease and mitigate bycatch of sea turtles, there are no such measures for the recreational fisheries of North Carolina. Both commercial and recreational fishing contribute substantially to North Carolina’s coastal economy, and recreational fishing continues to grow, building on a long history of pier fishing on North Carolina’s coast. Taking lessons learned from bycatch mitigation in the commercial longline fishery presents a good starting point for similar studies in the recreational rod and reel fishery. To address a research gap, and in support of a NOAA initiative to better understand and consider how to reduce sea turtle bycatch at recreational fishing sites, I analyzed incidental sea turtle captures in North Carolina reported in the Sea Turtle Stranding and Salvage Network (STSSN) database over 15 years. My aim was to examine incidentally captured sea turtle demographics and any trends between reported captures and fishing methods. To complement my historical data analysis I conducted surveys with fishers (anglers) on three piers in Carteret County to investigate cofactors of fishing methods and sea turtle incidental captures in order to make recommendations to inform potential mitigation measures, such as voluntary gear modifications. Historical data were obtained from STSSN from 2008 to 2022. The survey was created by NOAA for their Reducing Sea Turtle Bycatch at Recreational Fishing Sites Project. We sought information about angler habits including fishing methods (hook type, bait type), and frequency of sea turtle interactions. Outreach on the importance of reporting bycaught sea turtles was done opportunistically, most often after the final question: “What would you do if you accidentally caught a sea turtle?”. I directed anglers to the STSSN signs that were posted at the entrance to the pier and discussed the importance of these data, even if the “turtle seems fine.” I conducted data analysis and testing for statistical significance in R, and performed spatial analysis and construction of a publicly available spatial GIS tool through arcGIS Pro. From 2008 to 2022 there were 427 reported interactions with sea turtles with recreational rod and reel fishers from piers in North Carolina. I examined relationships between species, geographical location (county), hook location, hook type, and season. Kemp’s ridley sea turtles represented 60% of reported interactions overall, and based on these reported interactions, are statistically more likely to be caught than any other sea turtle species. Overall the most reported captures occurred in May, though monthly numbers of incidental captures varied by county. Shrimp was the most commonly used bait type in incidental sea turtle captures and j-hooks were the most often reported hook type. Kemp’s ridleys had the highest number and proportion of captures by the mouth. Captures by the mouth comprised the largest percentage of each species' known hook locations; only greens and loggerheads had a nearly equivalent amount of captures by mouth and flipper. I conducted 77 angler surveys in the fall of 2023, capturing data for 150 anglers at three piers in Carteret County: Bogue Inlet Fishing Pier, Oceanana Pier, and Newport River Pier. The 1 first half of the survey covered general fishing habits and preferences. Most fishers interviewed preferred fishing in the spring and fall. Shrimp were statistically more likely to be chosen as bait, and j-hooks most likely to be chosen for hook-type. Twenty-seven percent of respondents spent at least 16 days fishing in at least one season (3 months), while 49% of respondents were only visiting North Carolina, spending 5 days or less at the pier per season. Angler surveys indicated there is likely significant under-reporting due to local fishers perceiving easily dehooked and healthy turtles as unnecessary to report. There are several key points to consider when interpreting the results of this study. First, relationships between co-factors and incidental captures are difficult to reliably determine because little baseline data exist to compare to. When conducted at a state-wide scale, the angler survey data will provide additional background data and therefore allow for better analysis of potential cofactors with incidental captures in the future. Self-reported data always presents challenges, as it is impossible to know whether increases in reports are due to a true increase in incidental takes or if they are due to increased reporting. While attempting to control for the background popularity of j-hooks and shrimp, use of these bait and hook types were not statistically significant, suggesting that those are the most common hook and bait types associated with incidental takes because they are also the most common hook and bait types used at the piers. There was no relationship between where sea turtles are hooked (mouth or flipper) based on hook type. This result is counter to what might be expected from the success of switching to circle hooks in the commercial long-line fishery. A possible explanation is that the circle hooks used by pier anglers weren’t large enough to prevent swallowing the hook. At the end of any good research study, there are more questions to be answered. I will incorporate habitat data into my sea turtle maps to obtain distances of piers to preferred sea turtle habitat. Will this help inform which sea turtle species are most often reported as caught at that pier or the level of incidental captures generally? After answering this question, I will publish the analysis of the historical data including the dashboard tool. I am hoping the dashboard tool can be used to suggest trends that can inform potential mitigation measures. A few potential voluntary measures that could decrease bycatch at the piers in North Carolina include temporary restrictions. One option is to implement temporary closures during the months of highest incidental captures at each pier, for example a temporary closure in May for Carteret and Pender Counties. The other option is to enforce bait restrictions, restrict bait use apart from lures or gotcha plugs during months of highest incidental captures. The finding the captures by the mouth were most common in all species indicates that this may reduce incidental captures of loggerheads, Kemp’s ridleys, and green sea turtles that are likely attracted to the bait as a food item.
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Sajewski, Amanda (2024). Hooked! An Analysis of Sea Turtle Bycatch in the Recreational Rod and Reel Pier Fishery of North Carolina. Master's project, Duke University. Retrieved from https://hdl.handle.net/10161/30610.
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