Understanding the dynamics of groundfish fisheries
has important implications for fisheries management. It allows researchers
to put in perspective the effects of removals from directed fisheries
and by-catch fisheries. Directed fisheries are those that target one
species. By-catches are also made of secondary species. These by-catches,
however, may be important when the directed fishery is relatively
large, or when the by-catch species is threatened. Management regulations
have been put in place to limit the amount of by-catch. However, it
is important that the by-catch limits reflect reasonable expected
levels. If the limits are too low, then discarding of by-catch species
is encouraged.
The species composition of landings reflects
the mixture of species on the fishing grounds and the selectivity
of the fishing gear used. Individual groundfish species occupy specific
habitats defined by factors such as water temperature, bottom type,
and water depth. Consequently, their spatial distributions reflect,
to a certain extent, variations in their preferred habitats. Their
spatial distributions also vary seasonally. Cod, plaice and white
hake leave the Bay in the late fall and overwinter in deeper waters
of the Laurentian Channel at the mouth of the Gulf of St. Lawrence.
Winter flounder, on the other hand, are thought to overwinter in coastal
estuaries. Some fisheries concentrate on migrating fish due to their
more aggregated distribution. Others concentrate on feeding distributions.
During the fishing season, cod and plaice tend to be found in deeper
and colder water than white hake and winter flounder. But, there is
considerable spatial overlap among these species. Over the years,
knowledge of these patterns allows fishers to predict the species
mix of their catches based on their fishing location and timing.
Fishing gears are also selective, both of the
size of fish and the species. The size of meshes in otter trawls,
seines and gillnets, and the hook and bait sizes used on longlines
will affect the sizes of individual fish caught. Larger meshes, hooks,
and baits will catch larger fish. Plaice and winter flounder have
smaller mouths than white hake and cod of the same size, and this
results in few plaice and winter flounder being caught on longlines.
Gillnets are normally used for cod and hake, possibly because the
flatfish species remain closer to bottom. In summary, the type and
size of gear will affect the size and species composition of the catches.
In this section of the report we describe the
main fishery types in St. Georges Bay groundfish fisheries. These
fishery types were defined based on the species composition of landings
and the fishing gear used. Changes in the mix of fishery types during
the study period are described as well as their geographic locations.
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