Estimating abundance from gillnet samples with application to red drum ( Sciaenops ocellatus ) in Texas bays
A model of gillnet selection is developed to accommodate the possibility that some catch observations will be known more precisely than others and allow for nonlinear relationships between the selection parameters and mesh size. The model is used to show that gillnet selection for red drum (Sciaenop...
| Published in: | Canadian Journal of Fisheries and Aquatic Sciences |
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| Main Authors: | , , |
| Format: | Article in Journal/Newspaper |
| Language: | English |
| Published: |
Canadian Science Publishing
2002
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| Subjects: | |
| Online Access: | http://dx.doi.org/10.1139/f02-034 http://www.nrcresearchpress.com/doi/pdf/10.1139/f02-034 |
| Summary: | A model of gillnet selection is developed to accommodate the possibility that some catch observations will be known more precisely than others and allow for nonlinear relationships between the selection parameters and mesh size. The model is used to show that gillnet selection for red drum (Sciaenops ocellatus) in Texas bays may be explained as a unimodal process approximating a skewed Laplace distribution, where the optimal length varies in proportion to mesh size and the variance in proportion to the optimal length. It is also suggested that the number of encounters with the net ought to depend on swimming speed of the quarry, which in turn varies predictably with length. This information, along with the estimates of selection, is used to develop indices of abundance for each length-class. The results indicate that the recruitment of year-old red drum to Texas bays has fluctuated markedly since 1975, but without any persistent trends. However, the survival of these and older fish has increased dramatically owing to various regulations promulgated since 1981. |
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