Title

The fishery for Argentine hake (Merluccius hubbsi) and oceanic processes in the southwestern Atlantic Ocean

Date of Award

1987

Availability

Article

Degree Name

Doctor of Philosophy (Ph.D.)

Department

Marine Biology and Fisheries

First Committee Member

Francis Williams, Committee Chair

Abstract

The fishery for Argentine hake (Merluccius hubbsi) was examined using data from the Argentine offshore fishing fleet and research cruises for 1978-1979. The composition of the Argentine fleet required the standardization of fishing effort, via the determination of relative fishing power (RFP). The RFP of a fishing vessel was found to increase almost linearly for engine powers between 300 and 1000 HP, remaining fairly constant at greater engine powers.The second part of the study provides a statistical description of the commercial fishery data, concentrating on CPUE and its validity as an index of relative abundance. The monthly frequency distributions of hake CPUE were examined to select adequate statistical estimators and to gain insight into the dynamics of fish concentrations and fishermen. Four characteristic shapes of CPUE frequency distribution were identified corresponding to intra-annual changes in the spatial aggregation of fish due to environmental and behavioural factors and corresponding changes in deployment of fishing effort.A third part of the dissertation examines the annual migratory pattern of hake. Hake show an annual north-south, offshore-inshore migration between feeding and spawning grounds. The oceanic processes that shape the migratory pattern were discussed as they affect the availability of forage and the survival of hake larvae. An apparent difference in the northern extension of the migration was found between years: in 1979 hake were found approximately three degrees latitude further south along the shelf break than in 1978. The difference was linked to apparent changes in the location of the convergence of the Brazil and Malvinas currents.The final part of the dissertation examines the effect of sea surface and bottom temperature on the distribution of hake. Discriminant analysis separated fishing stations with high and low abundance of hake. Bottom temperature contributed more than SST to the separation in autumn-winter, but both variables were equally relevant during spring-summer. Large numbers of hake were found at bottom temperatures between 6-8$\sp\circ$C year-round, whereas the sea surface temperatures associated with dense hake concentrations fluctuated seasonally. Geographically, the stations with high abundance of hake were always located on the middle and outer shelf, bound by shallow coastal waters and the shelf break. (Abstract shortened with permission of author.)

Keywords

Biology, Oceanography

Link to Full Text

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