2. Study descriptions
In this paper, we compare the methods and results of seven studies (Fig. 1) focused on derelict trap debris resulting from both commercial and recreational fishing. This field of research is developing, and data collection using common metrics proved difficult. The studies reported here are some of the first in the United States to take a systematic approach to understand the extent of the derelict fishing trap issue. Estimating mortality caused by derelict gear remains challenging and thus economic impact is even more difficult to reliably estimate. For each study, the amount of DFTs present in the fishery was assessed. The studies used multiple techniques to determine the quantity of trap debris, which are fully described in Table 1. Generally, researchers found that visible detection by cameras or divers worked well in high visibility conditions (shallow and clear water), while sonar was most adaptable to wide ranges of depth and visibility conditions outside of reef or highly variable substrate types. Most studies chose to stratify the study area by the level of commercial fishing effort, and included this variable in subsequent analysis. Ghost fishing and habitat impact assessments were conducted based on study objectives. A mixture of in-situ assessment methods were used by various investigators; for example, divers assessed catch contained in ghost pots (Maselko et al., 2013) and researchers used field experiments to simulate and evaluate the effects of derelict fishing traps on target species and habitat (Clark et al., 2012 and Havens et al., 2008). Because each study was designed to address specific regional challenges associated with DFTs, the focus of each study varied. For example, the North Carolina study focused on the impact of DFTs on the diamondback terrapin (Malaclemys terrapin), while the USVI study focused on better understanding the fishing community. Meta-analysis was challenging given differences among study design and scope. Statistical analysis on common metrics (e.g., number of DFTs) was not possible given the different methods of data collection. Therefore, our analysis is mainly qualitative and highlights the need for standard reporting metrics to facilitate comparisons. We provide some economic implications for the estimated impacts of DFTs, highlighting a case study comparing the ghost fishing capture rate to the entire fishery, and utilizing additional published literature to expand outside the seven studies reported here