Catch studies indicate more red snapper since 1992.
Catch per unit of effort (CPUE) is a simple and extremely useful index of stock abundance. Often it is used to diagnose unsustainable fishing of a species.
It is a relative index of abundance, used to indicate directional changes (such as increases or decreases).
The "catch" can be expressed as the total weight of an entire catch or that of a certain species. Likewise, numbers of fish caught could be used in this index, as well. The "unit effort" has a time component, either by hour or per "angler trip." Included in effort is an index of gear used, for example, number of hooks in the water, gillnet sets, vessels, or simply per angler. Careful attention must be given to the units when comparing CPUE datasets.
The SEDAR 15 document--the scientific basis of the changes currently being considered by NOAA and its South Atlantic Fishery Management Council--provides CPUE information on red snapper harvesting from three distinct groups: commercial fishermen, headboats (for hire vessels that generally charge a fee per angler, typically accommodating 2060 passengers), and recreational fishers (SEDAR 15 SAR 1 SECTION II Pt 5).
In general, the data collected from the three user groups show an increase in CPUE indices and suggest the stocks have been increasing since the regulations were enacted in 1992. (See figure.)
The commercial CPUE (expressed in pounds per hook-hour), headboat CPUE (in number per hook-hr) and recreational CPUE (in number per angler-trip) all show a positive slope. The three datasets, collected from three different groups using different techniques and units, all show the same trend--an increase in CPUE, and thus, one can surmise that there have been the associated increases in red snapper stocks.
The enhanced regulations of 1992 seem to be working to increase red snapper stocks, but not deemed fast enough according to goals set by federal authorities based on estimates of what abundance may have been in the 194582 period.
We conclude, however, that the CPUE data, coupled with the researchers' other data over the past quarter-century, point to a growing stock.
Raymond E. Waldner
Ph.D., Professor of Biology
Ph.D., Associate Professor of Biology
Palm Beach Atlantic University
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|Title Annotation:||SPECIAL REPORT|
|Author:||Waldner, Raymond E.; Chesnes, Thomas C.|
|Date:||Nov 1, 2009|
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