Modeling the transport of East Kamchatka pollock eggs and larvae taking into account tidal dynamics

The work examines the drift of pollock eggs and larvae in the Pacific Ocean region adjacent to the southeastern coast of the Kamchatka Peninsula and the northern Kuril Islands. A model approach is used, combining particle trajectory calculations using the ICHTHYOP software, ocean reanalysis data, and the results of a regional tidal model. The eggs and larvae are considered as passive tracers, and their transport from the main spawning ground of the East Kamchatka pollock in the deep-water canyon of the Avacha Bay was calculated for one month in 2024 and 2025, starting from the observed spawning date in April.

The main objective of the modelling was to determine the influence of various dynamic factors on particle transport and the likely locations of their accumulation, where egg development and larval hatching may occur. Identifying these locations through ichthyoplankton surveys is very difficult. The model calculations did not take into account a number of factors related to the mortality of eggs and larvae under the influence of environmental changes and predation, larval activity during development, and other processes of physical and biological interaction. The transport of tracers after their ascent to the surface in the spawning area was analyzed using background surface currents and those averaged over the upper sea layer.

The simulation results show that the predicted horizontal particle trajectories depend not only on the different hydrodynamic conditions for the two years, but also on the consideration of tidal drift. A hypothesis has been put forward regarding the dynamic conditions favorable for the development and survival of pollock eggs and larvae, under which their drift does not lead to their transport from the shelf water into the open ocean. Potential areas of particle accumulation in coastal waters have been identified.

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