Low species diversity and good body condition of bycatch in the southern Gulf of St. Lawrence American lobster fishery
The American lobster fishery is one of the largest and most important in the southern Gulf of St. Lawrence and is considered to be sustainable and healthy.
The impact of the fishery on other species in the ecosystem however is not well understood.
During the summer and fall of 2015 a field study took place to examine potential ecosystem impacts of the southern Gulf of St. Lawrence lobster fishery from the perspective of the incidentally caught (or bycatch) species.
Read this open access paper on the FACETS website.
An organism was considered bycatch if it was not a commercial-sized lobster, specifically those lobsters that protected by conservation measures (for example their size or the presence of eggs), or a species or taxonomic group other than lobster.
The lobster fishery uses baited traps which are a lower impact gear that fishes while resting on the ocean floor. It is also assumed that any catch returned to the water are likely to survive because each trap is quickly emptied by hand.
To establish a baseline of bycatch diversity and condition for the fishery, the incidentally caught species were counted, measured, and observed for injuries.
The fishery is very good at catching small lobsters even though the traps are designed with slots large enough for small lobster and other species to exit.
From the 73 fishing trips and 19337 traps sampled, the most common bycatch were undersized male and female lobsters. Other than lobster, 27 different groups of organisms were recorded, 23 in the spring fishery and 16 in the summer.
Atlantic rock crab (male and female) were the next most common species of bycatch followed by the fish commonly known as cunner in the spring fishery and hermit crabs in the summer fishery. Nearly all of the catch was alive and in good condition at the time of being returned to the water despite exposure to air and warm temperatures.
These results further support that the gear type, the low diversity of bycatch, and the hand-sorting of the trap likely minimize the impact the lobster fishery has on incidentally captured animals.
The outcomes are encouraging, though continued monitoring of the undersized and egg-bearing lobsters caught in the fishery is important to support stock health.
Fisheries bycatch monitoring will be required to take into account the total fishery catches and to track any changes in the catch composition in response to the environment.
This will be important for an ecosystem approach to fisheries management which includes taking into consideration all sources of mortality for stock assessments, in addition to other current and upcoming conservation concerns for bycatch species.
Read the paper — Baseline composition, quantity, and condition of bycatch in the southern Gulf of St. Lawrence spring and summer American lobster fisheries by Stephanie A. Boudreau and Patricia H. Hanley.
