Coho salmon of Kultuchnoe lake

 

Kultuchnoye Lake is a unique corner of nature in the very center of Petropavlovsk-Kamchatsky, an intensively developing city, a place of attraction for its residents and guests. The development of urban infrastructure, as well as the formation of a comfortable recreational environment around the lake, have led to inevitable negative consequences for the reservoir ecosystem. In historical retrospect, Kultuchnoye Lake was a large fattening and spawning reservoir for salmon fish, the "calling card" of the Kamchatka ichthyofauna. However, during the process of urban development, the tributaries of the lake and large springs were filled in, in which, according to historical data, coho salmon and sockeye salmon spawned - one of the most valuable species of salmon fish. Currently, typical inhabitants of the reservoir are three-spined and nine-spined stickleback, as well as silver carp, introduced into the reservoir about 20 years ago. These species, unlike salmon fish, are less demanding on the quality of water and bottom substrate.

 

Despite its accessible location and colossal anthropogenic load, Lake Kultuchnoye has not been an object of ecosystem monitoring until recently, and hydrobiological and ichthyological surveys of the lake were carried out irregularly. However, environmental education among the population of the region and the development of tourism forced people to pay attention to the state of the reservoir and raise the issue of measures for its restoration and preservation. As a result, there was an urgent need to assess the state of the lake ecosystem. In recent years, through the efforts of employees of the Kamchatka branch of the State Research Center of the Russian Federation "All-Russian Research Institute of Fisheries and Oceanography" (VNIRO): specialists from the laboratory of fisheries ecology and the laboratory of salmon fish, observations of the state of Lake Kultuchnoye have acquired the status of monitoring.

 

A recent ichthyological survey in the lake's waters yielded unexpected and very encouraging results: juvenile coho salmon were found among the ichthyofauna. Three immature individuals, one of which was about 12 cm long and two (male and female) - about 16 cm, were caught in the southwestern part of the lake, not far from the channel connecting the reservoir with Avacha Bay. An examination of the scales (the "biometric passport" of salmon fish) made it possible to determine their age: the smaller individual was a "two-year-old", the larger fish were "three-year-olds". It is known that before migrating to the sea to feed, coho salmon spends from 1 to 3 years in fresh water, but under certain conditions it may not leave the spawning and feeding reservoir at all, forming the so-called residential form. In Kamchatka, the residential form of coho salmon is not a widespread, but well-known phenomenon. Further research will determine whether the coho salmon caught in Lake Kultuchnoye are representatives of the resident form, or whether the reservoir has limited opportunities for reproduction and fattening of the migratory form.

 

The retention of immature individuals in fresh water may be a consequence of favorable feeding conditions. A study of the stomach contents of the caught coho salmon showed that both large individuals fed intensively, and in addition to adult insects, the food included fish (young sticklebacks) - a high-calorie food item saturated with the necessary protein and fat. At the same time, it should be noted that it is the transition from feeding on invertebrates to predation during the fattening period of young coho salmon in lakes that is an integral stage in the change from a migratory lifestyle to a resident one.

 

Probably, a small number of migratory coho salmon producers could have entered the lake in previous years and left offspring. This is all the more likely since in recent years there has been an increase in the number of Kamchatka coho salmon, which entails the development of reservoirs by this species that have not been used for reproduction for a long time.

 

To find out what life form the young coho salmon found in Lake Kultuchnoye belong to is the task of the upcoming studies. Nevertheless, the very fact of finding salmon fish in a reservoir, for the ichthyofauna of which salmon were considered lost for many years, is a significant event. There is reason to believe that the ecosystem of the reservoir, despite many years of destructive impact, has not lost the ability to self-restore. And this circumstance must be taken into account when developing measures to restore and preserve this unique reservoir, carefully weighing the possible consequences and strictly adhering to the principle of "do no harm".

 

Press service of VNIRO