Justification of the parameters of twin fishing for Far Eastern mackerel and Ivashi sardines by medium tonnage vessels, taking into account their fishing biological characteristics

In the Northwestern Pacific Ocean, in recent years, there has been an increase in the populations of eastern mackerel (Scomber japonicus) and Far Eastern sardine (Sardinops sagax). In the Far East, large-tonnage fishing trawlers capable of successfully harvesting (catching) mackerel and Far Eastern sardines are engaged in fishing for pollock and other traditional objects of fishing. The purpose of this article is to show how underutilized stocks of mackerel and Far Eastern sardine can be developed by medium tonnage vessels using twin fishing techniques. For the biotechnological substantiation of the parameters of the twin trawl system according to the degree of influence on the object of production (catch), it was divided into 7 zones, in eachof which the object of production (catch) has one or another behavioral reaction. The article substantiates the necessary (optimal) vertical opening of the mouth of the trawl for complete vertical fishing of schools of fish based on echometric diagrams of the vertical distribution of schools of mackerel and Far Eastern sardine and the accepted response distances of fishing objects to elements of the trawl system. The biotechnical substantiation of the parameters of the twin trawl system for the extraction (catch) of Pacific mackerel and Far Eastern sardine has been carried out. The length of the twin trawl, the angle of attack of the upper, lateral and lower layers of the trawl shell, the length of the wings of the trawl are determined, the necessary ratio of the shaded area of the shell of the trawl to its fictitious area for mediumtonnage vessels with different traction characteristics is determined. Based on the speed parameters of fish in different zones of the trawl system, the distance between twin vessels, the length of the cords and the length of the cables are determined