Fishing success, measured in terms of catch
per unit effort, is commonly used as an index of the abundance of
fish stocks. The basic idea is that the more fish that are caught
with a fixed amount of fishing effort, the larger the population of
fish is. While a higher catch per slip may indicate a more abundant
population, several other factors may influence catch rates. For example,
the area fished, the season fished, the type of fishing gear used,
the amount of gear used, the experience of the fishers, and technological
improvements. We have attempted to take as many of these factors as
possible into account in our analysis of catch rates. We have restricted
analysis to the four fishery types where one species is by far the
dominant part of the landing, and we have omitted mixed fishery types.
A statistical model was used that allowed for the inclusion of effects
such as gear, month of fishing, and the fishing vessel. Nonetheless,
it is quite possible that some important factors have not been included,
and we would appreciate receiving suggestions of other things to try.
In this report, we have used the number of purchase slips as a measure
of the amount of fishing effort, and catch per slip as a measure of
catch per unit effort.
The following table summarizes the number of
purchase slips available for the catch rate analyses, by species and
gear. There was considerable variation in the numbers of purchase
slips available for analysis among these groupings. In order to avoid
undue influence from relatively small numbers of observations, we
used the criterion that there had to be at least 10 observations per
species, gear, year group for inclusion in the analysis.
| SPECIES |
GILLNET
|
LONGLINE
|
OTTER TRAWL
|
SEINE
|
| WHITE HAKE |
2320
|
5173
|
846
|
135
|
| PLAICE |
|
|
2221
|
871
|
| WINTER FLOUNDER |
|
|
4005
|
|
| COD |
|
|
|
207
|
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