Statistical analysis of catches by trawling in the fishing regions of the eastern Adriatic in 1951
Abstract
This preliminary paper does not attempt to arrive at any definite conclusions. That is left for a continuous and more detailed qualitative and quantitative analysis of fish stocks. The conclusions which may be drawn from this statistical analysis are the following:
1. The relative density of fish stocks in our open territorial waters is greater than in the coastal waters and channels. This is the more important in that our more intensive post-war trawling is still carried out in coastal waters and channels.
2. A slight decrease in catch per unit of time has been observed in this more intensive trawling. In order to build up the fish stock it would be necessary to prohibit trawling by ships of over 80 HP (in some regions over 50 HP), at least for a short period.
3. Any increase in the amount of fish taken from inshore waters and channels may result in a further regression per unit of effort. The number of vessels and the amount of time spent, which show a constant tendency to increase, may speed up this process.
4. Underfishing in some regions during, or even after, the second World War changed the quantitative proportions within the composition of stocks in individual fishing regions. The predators have multiplied whilst the number of plant-eaters and those which feed on invertebrates has decreased considerably.
5. The more intensive post-war trawling has changed the relative amounts within the stocks. The quantities (by weight) of the Gadidae have increased considerably and those of Selachia have decreased in the annual average. This applies particularly to the southern area in the Velebit Channel.
6. The average lenght of Merluccius vulgaris, our most important commercial species in deep-sea trawling, is constantly decreasing through the years, as shown by periodic investigation.
7. It would be necessary to carry out as speedily as possible, the qualitative and quantitative examinations of the fish stocks in the channels and inshore waters of our most important fishing regions. In this way the real situation could be determined and the possibility of overfishing be eliminated in time.
