Influence of Water Salinity on the Growth and Survivability of Asp Larvae Leuciscus aspius (Linnaeus, 1758) under Controlled Conditions

SIMPLE SUMMARY: Serious biological imbalances are often caused by poorly thought-out and destructive human activity, but also by progressive climate change. Each of these factors has an enormous impact on the life of terrestrial and aquatic organisms, including fish. As a result of the anthropogenically altered river environment, individual species must migrate from typically fresh to brackish waters that form in river mouths in order to conduct natural life processes such as spawning, as well as in search of food. An excessively high salinity level can be fatal to freshwater finfish, but low salinity can positively affect the growth and survival of larvae, fry and adult fish. ABSTRACT: The effect of water with a salinity 3, 5, 7, 9 and 11 ppt on the growth and survivability of asp Leuciscus aspius (L.) larvae was investigated. A control sample consisted of asp larvae reared up in freshwater (0 ppt). Larvae were fed for 21 days with nauplii of the brine shrimp Artemia salina. Water salinity was observed to have a considerable effect on the growth and survivability of asp larvae. In addition, saline water extended the life span of Artemia salina nauplii, which resulted in their prolonged availability to asp larvae. Asp larvae showed low tolerance to the salinity of water, reaching 9–11 ppt. Depending on the degree of salinity, the mean final weight of larvae varied from 122.6 to 139.4 mg, at body lengths from 23.8 to 25.6 mm, respectively. The best body length increments were recorded among asp larvae maintained in water with a salinity of 3 ppt. Depending on the level of water salinity, the final survivability of asp larvae ranged from 16.9 to 94.5%. The highest and increasing mortality was demonstrated among the larvae reared in water of the salinity equal to 11 ppt. It is not recommended to rear asp larvae in water with a salinity above 7 ppt due to the low survivability and large differences in the body size of the larvae that managed to survive.