Derelict fishing gear can create a lot of problems: hazards to navigation, damage to sensitive habitats, and ghostfishing. Ghostfishing occurs when lost or discarded fishing gear that is no longer under a fisherman’s control continues to capture marine life. This is obviously bad news for local marine animals that can end up ensnared in derelict gear, but it can be harmful to local fisheries too. That’s what scientists at the Virginia Institute of Marine Science (VIMS) think and set out to prove.
VIMS researchers considered that apart from the obvious financial loss of losing gear, fisheries may suffer due to competition between active and derelict gear, specifically blue crab pots. Their research and analysis, funded in part by the NOAA Marine Debris Program, evaluates the hypothesis that derelict crab pots compete with active gear by attracting target species that might otherwise be attracted to actively-fished crab pots. This reduces commercial fishery harvests and revenues and is thus a lose-lose situation for both the crabs and crabbers.
To test this hypothesis, VIMS researchers created a model that allowed them to assess fishery harvests in Virginia with and without derelict gear present. Using this model, they compared fishery harvests with derelict crab pots removed via a large-scale removal project, and a hypothetical scenario where no pots were removed. The comparison also accounted for other factors that could potentially impact harvests, such as stock abundance and environmental conditions, so that the effect of derelict gear removal could be isolated.
The results of this comparison indicated that the Virginia Marine Debris Location and Removal Program, which removed 34,408 derelict crab pots over six years, increased crab harvests in Virginia by 27%, or by 30 million pounds valued at $21.3 million for fishermen! This was the direct result of reduced gear competition and thus the improved efficiency of active crab pots. Removal was found especially effective in highly-fished areas with higher rates of pot loss. Extending their findings globally, VIMS researchers speculate that removing about 10% of derelict pots and traps could increase crustacean harvests by over 600 million pounds per year. These findings exhibit just one of the many damaging effects of derelict fishing gear.
This study and its results were accepted for publication by the journal Nature Scientific Reports (for you non-science folks, that’s a big deal), with VIMS researchers A. M. Scheld, D. M. Bilkovic, and K. J. Havens as authors on the paper. For more on these and associated efforts, check out the NOAA Marine Debris Program website.