Caracterización del proceso de descarte de merluza (Merluccius hubbsi) en la flota de buques congeladores y factorías. Resultados preliminares a partir de los datos recolectados por observadores del INIDEP en seis mareas realizadas entre agosto y diciembre de 1995.
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Pursuant to SAGyP resolution No. 814/93, during August-December 1995, six INIDEP Fishery Observers trips on board of processing vessels of the Argentine fleet were carried out. They represented 256 navigation days, 232 effective fishing days, 725 fishing trawls and 2,245 trawling hours. Data measured on board were compared to those reported in the fishing log corresponding to the same cruise and submitted to the DNPyA by the Skipper. Catches observed and reported differ by 3985,7 t (28.2. ), with a maximum difference of 1,200 t in a single cruise. In the case of trawling hours, an important fluctuation of values was observed and, in two cases, the number of hours declared exceeded those actually performed (111 and 72). In the other four cruises, between 3 and 17 trawling hours less were reported. The yields (CPUE) also showed differences that ranged between 40 and 5.320 kg/h. Taking into account the fishing log data, a CPUE of 4252.8 kg/h was estimated against a real value of 6299.1 kg/h observed on board. Conclusions derived from the analysis of the information gathered by the personnel on board as regards operational and technological aspects can be summarized as follows: 1) sampled vessels use bottom trawl nets with reduced mesh span, frequently in areas of large juvenile concentrations; observers verified that catches showed no relation with the factory processing capacity which implies that there is a trend to catch much more than what can be processed. There is no control on what enters in the net to regulate trawl duration. In general, trawl frequency and duration are independent of the presence of raw material in the plant to saturate lowest points; 2) discard level is very high and related to variable criteria difficult to predict. To a large extent this is conditioned by the previous item, since bad quality fish is rejected or the processing line accelerated too much. This is not exclusively associated to fishing gear selectivity; 3) failures were detected in the processing lines that can be attributed to calibration and maintenance of the equipment, to handling and selection of specimen by operators and to the quality of raw material (crushed fish that block the machinery). All those factors diminish yield and increase discard and 4) significant differences between the information recorded on board and that declared in the fishing log were detected. The difference in the catch value is due to discards and to the conversion factors used to recalculate the nominal catch. It is important to highlight that errors in the trawling hours report were detected and that it affects the procedure used to recalculate fleet catches based on the information derived from sampled vessels (CPUEobs). 1995 official statistical data were analyzed and 51 hake-fishing factory trawlers selected. Assuming that 6 cruises are an efficient sampling of the activity of the 51 vessels selected, catch was recalculated from the catch-per-unit-effort observed (CPUEobs) and the declared effort (trawling hours). Taking into account the incidence of uncertainty associated to fishing statistics on resource evaluation and management, it is extremely important to improve the basic information available, especially on the size and age groups discarded. In this sense, we propose: to analyze the feasibility of implementing a fishing log with better temporal and spatial resolution, preferably with a report of activities trawl by trawl; to implement a more intensive application of the Fishing Observer Project on the hake-fishing fleet. This would start with a 10 to 20. coverage on freezers and factory trawlers. Later, ice chilling vessels should be added. This would allow to adjust fishing statistics, to obtain fishery-biological information directed to resources evaluation and to better recognize the technical-operative aspects of the fleet (capture and processing).