The magnitude and spatial distribution of fishing effort in the Gulf of Mexico penaeid shrimp fishery has been the subject of great contention. Here, we describe a simple and inexpensive electronic logbook (ELB) and algorithms tested to describe the temporal and spatial patterns of fishing effort, based on nothing more than the position of the vessel at 10-min intervals; these algorithms were tested with 788 tows (4,558 h of trawling). On average, the difference between ELB estimates and recorded levels of effort were less than 1%; spatial agreement was also good. On a spatial basis, ELB estimates accounted for more than 84-97% of the variance observed in recorded effort, depending on the grid size used in the analysis. Further, analysis of data from more than 18,000 tows yielded a strong within-trip relationship between catch and effort. This relationship enables accurate allocation of the total landings from a trip to the subareas fished, based on nothing more than trawling times within each subarea fished. Because National Marine Fisheries Service port agents already collect landings on a trip total basis, a large-scale installation of inexpensive (ϽUS$500) ELB units should be able to measure shrimp fishing effort accurately.
Hydrography data from 1985 to 1993 in the vicinity of the Endicott Causeway near Prudhoe Bay, Alaska, were analyzed to determine if the trend in yearly post-causeway construction temperature and salinity was toward colder and more saline conditions. No significant (p ≤ 0.05) relationship was found for temperature; however, salinity levels significantly decreased with time following construction. Intra-year variations in hydrographic conditions appeared to be due to coast-wide meteorological and oceanographic events rather than causeway-induced. We analyzed abundance indices, as log e transformed catch-per-unit-effort (CPUE), of four marine species (arctic cod, Boreogadus saida; fourhorn sculpin, Myoxocephalus quadricornis; arctic flounder, Pleuronectes glacialis; saffron cod, Eleginus gracilis); two freshwater species (round whitefish, Prosopium cylindraceum; arctic grayling, Thymallus arcticus); and the anadromous rainbow smelt, Osmerus mordax, to determine whether there were increases in the abundances of marine species and declines in anadromous and freshwater species. We developed the "best-fit" regression models, based on the criterion of maximized regression F-ratio (i.e., minimized regression p-values), using year, temperature, salinity, and all possible interactions. Results suggested that all species exhibited changes in abundance levels over the period of record. In particular, arctic flounder and rainbow smelt both showed sharp increases in abundance five years after construction. For all species, the observed changes in abundance levels appeared to be due to naturally occurring events in the species' life histories or changes in coast-wide meteorological conditions rather than to causeway-induced alterations in local hydrographic conditions.
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