Экология глубоководного нереста восточнокамчатского минтая

Abstract

Walleye Pollock is one of the most widespread fish species in the North Pacific and an important fishery. There is an East Kamchatka population of this species off southeastern Kamchatka and the northern Kurils. In 2000-2004 in the area of deep-water canyons of Avacha (Severny, Tsentralny and Yuzhny) and Kronotsky Bays the hydrological conditions, ecology of pollock spawning and its scale were studied. In 2022-2024 the research was resumed, significant changes in hydrological conditions and their possible impact on the vertical distribution of pollock eggs were revealed. The aim of the work is to summarize all data available to date on deep-water spawning of East Kamchatka pollock. The results of integrated (ichthyoplankton and hydrological) surveys carried out on a standard grid of stations in April-May 2003-2024, frequent ichthyoplankton surveys carried out from March to May 2003-2024 at reference points located in the tops of canyons of Avacha Bay, layer-by-layer surveys in the canyons of Avacha and Kronotsky Bays, and observations during a fishing trip in March-April 1997 were used for the study.  It is shown that hydrological conditions in the canyons of Avacha Gulf in spring period undergo significant changes not only in interannual plan, but also on time intervals of tens of hours. Short-period fluctuations may be related to tidal water dynamics. In 1997, pollock spawning in Avacha and Kronotsky Bays occurred mainly in deep-water canyons. In the Severny Canyon, mass spawning was in the first decade of April, in the Tsentralny and Yuzhny Canyons - in the second decade of the month. Spawning concentrations in the canyons were characterized by vertical structure - males were located deeper than females. It was noted that in 2007, 2010-2011 an average of 60.5% of all pollock eggs of the East Kamchatka pollock population were counted in the canyons, with 44.4% recorded in the Severny Canyon. It was confirmed that the timing of mass spawning in deep-water canyons varies from year to year depending on thermal conditions. For the Severny Canyon, a reliable negative relationship between the date of spawning peak and the average water temperature in the 300-500 m layer weighted to the total number of pollock eggs and the average water temperature near the bottom on the shelf of Avacha Bay during the period of ichthyoplankton surveys was established. It was found that pollock spawning horizons in deep-water canyons of the Avacha Bay, determined by the distribution of eggs at the 1st stage of development (age 3 hours), change in interannual and seasonal aspects.

Keywords: Walleye Pollock Gadus chalcogrammus, Pacific Ocean, deep-water canyons, spawning, eggs, developmental stages, temperature, salinity, internal waves