UNDERSTANDING THE MECHANISMS OF WINTER SURVIVAL THROUGH BIOCHEMICAL ADAPTATIONS IN INVASIVE SPECIES OF ASIAN CARP

Bighead carp, Hypophythalmichthys nobilis, are a warm water species native to Asia, present in the Mississippi River Basin and were labelled as an injurious species by the US Fish and Wildlife Service in 2011. Concerns exist about how Asian carp may impact the multibillion-dollars annual sport fishery if they are able to invade the Great Lakes. However, a gap in scientific data exists regarding survival of young-of-the-year (YOY) Bighead carp in Great Lakes winter water conditions. An experiment was conducted from Nov. 2014 to Apr. 2015 which examined the survival, growth, and biochemical adaptations of YOY Bighead carp of different sizes subjected to winter water temperatures similar to those in Lake Erie.

Fifteen YOY fish from each of four categories, small (SK 0.18g) and large Koi carp (LK 0.49g), small (SBH 0.2g) and large (LBH 1.8g) Bighead carp were randomly distributed to six tanks. Two treatments were applied to simulate the presence or lack of winter food availability. Mortality and temperature data during the experiment were collected.

The current study specifically examined lipids, fatty acid composition, mineral levels, and crude protein, first prior to simulated winter onset, second when 50% mortality of the stock (LC50) was achieved, and finally following extended exposure to winter water conditions. LC50 was reached for two groups during the experiment, small Koi carp and small Bighead carp. Comparisons of polyunsaturated fatty acids (PUFA) in neutral lipid (NL) relative % at LC50 reveals significant differences between fasted SBH (22.51±0.24%) and SK (11.85±0.64%) while the ratio of n-3:n-6 fatty acids among groups are similar (SBH: 0.85±0.14; SK: 0.84±0.03). The polar lipid (PL) profile at LC50 follows a similar trend with fasted SBH (47.72±0.61%) conserving greater relative % of PUFA than SK (30.78±11.1%) while maintaining comparable n-3:n-6 fatty acid ratios (SBH: 2.87±0.17; SK: 2.52±0.89). Increased relative % conservation of PL PUFA by Bighead carp may well be an adaptation which preserves membrane fluidity allowing them to survive longer exposure to low temperatures than Koi carp. These results demonstrate that there is potential for YOY Bighead carp to survive Lake Erie short winter water temperatures (4 months).