Numerical modelling of the population of grey seal (Halichoerus grypus) from the Baltic Sea in the context of reduction of damage to fishing economy

Abstract The work is a source material for organizations dealing with the management of the aquatic environment, including regulating the population of species that pose a real threat to fishermen. Predators, which have no natural enemies in the Baltic Sea environment, including the grey seal, have been part of the conflict between fisheries users and ecologists for decades. As part of establishing a system for conducting grey seal population control programs that will not affect the number of colonies, but will only allow real control over the excessive exploitation of fishing nets by this species mathematical models have been created. Due to the difficulties in obtaining actual data as input data for modeling natural populations, the proposed model is based only on expert data, therefore it is dedicated only to the seal species. The development of the population size can be ensured depending on such factors as herd size, hunting and procedures for birth rate and mortality. On the basis of multivariate analysis and the application of the created algorithm, several sample schemes were formulated for the large and small grey seal swarm. The authors gave the government administration a tool to implement the anticipated programs limiting the size of the grey seal predator population.