Numéro : 2113 - Year : 1990
How to define and measure an index of the fishing effort
Dott. ing. G. MESSINA, Consiglio Nazionale delle Richerche, instituto di Ricerche sulla pesca Marittima, Ancona, ltalia
The trawling seems to be nowdays the main responsible of the overfishing and also of the notable fishery resources impoverishment namely of the bottom ones.
In order to face such a situation and to prevent its worsening, all the initiatives aimed at either reducing or not increasing the fishing effort are now encouraged.
In this context, a new trawler could be built, almost in Italy, only if an equivalent one, as far as the fishing effort is concerned, be pulled down or unrigged.
So a parameter is to be defined to measure the "fishing capacity" of two different trawlers.
An appraisal of the candidate quantities (gross tonnage, engine power, hold capacity, bollard pull etc.) as significant indexes of fishing effort is carried out in this paper.
The analysis cornes to the conclusion that the bollard pull is the most significant parameter in this respect.
A set of diagrams, checked by means of some experimental tests carried out on commercial trawlers, is given; they allow a direct evaluation of the pull in both bollard and trawling conditions for different propulsive solutions (conventional or ducted or c.p. propeller) .
Such diagrams are easily utilizable when foreseeing the pull performances if bollard pull tests could not be carried out.
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