Kokanee salmon, when the population is landlocked

Summary of species impacts derived from literature review. Click on an icon to find out more...

Environmental	Beneficial

Current research on the environmental impact of Oncorhynchus nerka in the Great Lakes is inadequate to support proper assessment.

Potential:
Stocked kokanee may or may not have an apparent negative effect. Some of the determining factors that may influence whether this species has negative impacts on a receiving ecosystem include waterbody size and depth, the forage base, stocking densities, other species present, and if early or late-run strains are stocked.

Kokanee was introduced to compete with and reduce native Utah chub (Gila atraria) populations in Flaming Gorge Reservoir. However, it was found that under food-limiting conditions, the Utah chub was the superior competitor and was not affected by the kokanee (Teuscher and Luecke 1996). Seeley and McCammon (1966) gave a detailed discussion of impacts of kokanee on other species. Some of the impacts listed included: large kokanee populations can inhibit trout production because of competition for zooplankton; introductions of kokanee into small lakes can adversely affect even strongly established populations of rainbow trout (Oncorhynchus mykiss); and late-run kokanee and brown trout (Salmo trutta) may compete for the same spawning areas, especially in lower stream reaches. Introduced kokanee were at least partially responsible for the disappearance of three cladoceran species in Lake Tahoe (Morgan et al. 1978).

There is little or no evidence to support that Oncorhynchus nerka has significant socio-economic impacts in the Great Lakes.As this species was deliberately stocked and is a sport fish, there is no evidence to suggest it has negative impacts on human health or recreation.,

There is little or no evidence to support that Oncorhynchus nerka has significant beneficial effects in the Great Lakes.

Potential:
Kokanee salmon is commercially important in its native range along the west coast of North America. In the Great Lakes, it was originally stocked in lakes Ontario and Huron in order to support recreational and potentially commercial fisheries. However, stocking in both lakes ceased by the early 1970s (Crawford 2001, Kocik and Jones 1999).

Although it was originally thought that kokanee could be beneficial as a prey species for lake trout (Salvelinus namaycush) (Crawford 2001), Seeley and McCammon (1966) cautioned that kokanee salmon's value as a forage fish may be overrated—the species may depress rather than bolster trout populations. Its presence may not enhance a fishery, especially in waters without a deep, cool, well-aerated hypolimnion. The species is not long-lived (2 years), and in many areas the fish is only accessible for fishing for short periods in the spring and fall. Therefore, the entire population may die off after only being briefly available to anglers.

Note: Check federal, state/provincial, and local regulations for the most up-to-date information.

Control
Biological
There are no known biological control methods for this species.

Physical
Sockeye salmon are a homing species, returning to their native stream for reproduction.  Barriers can be constructed and/or natural barriers augmented to prevent upstream migration and aid management and eradication efforts, though little research exists on effective barriers for Oncorhynchus nerka. Lintermans and Raadik (2003) noted 3 key aspects of successful barriers in relation to a rainbow trout control program: a 1.5 m or greater vertical drop; direction of water flow towards the middle in higher flows with no slower overland flow passing down the banks; and no deep pool below the barrier from which fish could jump.

The USACE Great Lakes and Mississippi River Interbasin Study notes the potential effectiveness of sensory deterrent systems in providing barriers to fish migration or eliciting fish movements (GLMRIS 2012). Specifically, the success of underwater strobe lights as studied by Maiolie et al. (2001) is cited.  Testing conducted on wild, free-ranging O. nerka in their natural pelagic habitat in two large Idaho lakes revealed that fish moved an average of 30-136 m away from lights in waters with secchi transparency of 2.8 to 17.5 m, with an 80% reduction in fish density within 30 meters of the strobe lights (Maiolie et al. 2001). Many large scale strobe systems consist of four individual lights that flash at a rate of 450 flashes/min., with an approximate intensity of 2634 lumens/flash (GLMRIS 2012). Maiolie et al. (2001) tested flash rates of 300, 360, and 450 flashes/min.

Chemical
Of the four chemical piscicides registered for use in the United States, antimycin A and rotenone are considered general piscicides, but no studies have been found of their effects on O. nerka (GLMRIS 2012).

Exposure to niclosamide, registered in the USA as a granular lampricide, wettable powder, technical grade product, and an emulsifiable concentrate, is known to be toxic to all fish species at 0.5 mg/L after a 48-h exposure (Clearwater et al. 2008). There are no available studies of its specific effects on sockeye salmon, though it has been used for control of aquatic snails, zebra mussels, and oligochaetes, and is also toxic to many crayfish, frogs, clams, algae, and other amphibian and fish species (Clearwater et al. 2008).

In a study on removal of toxic chemicals from water using activated carbon, Dawson et al. (1976) found that granular activated carbon is saturated by rotenone at 0.1 mg of rotenone per gram carbon, and cited other studies documenting 0.94-1.32 mg of rotenone adsorbed per gram of carbon. Antimycin was efficiently absorbed and did not saturate carbon because of the low doses used (Dawson et al. 1976).

Increasing CO2 concentrations, either by bubbling pressurized gas directly into water or by the addition of sodium bicarbonate (NaHCO3) has been used to sedate fish with minimal residual toxicity, and is a potential method of harvesting fish for removal, though maintaining adequate CO2 concentrations may be difficult in large/natural water bodies (Clearwater et al. 2008). Salmonids are considered to be among the most sensitive fishes to low dissolved oxygen levels, with a DO concentration of 1-3 mg/L sufficient to cause mortality or loss of equilibrium (Clearwater et al. 2008). However, CO2 is approved only for use as an anaesthetic for cold, cool, and warm water fishes the US, for use as euthanasia (Clearwater et al. 2008). Exposure to NaHCO3 concentration of 142-642 mg/L for 5 min. is sufficient to anaesthetize most fish (Clearwater et al 2008).

Low pH is known to affect fish behavior. Ikuta et al. (2001) documented the effects of low pH on sockeye salmon, noting that salmon would not swim upstream into areas of pH lower than 6.0. Acute exposure to low pH levels can directly kill fish by discharge of sodium and chloride ions from body fluid, and sub-lethal levels can affect reproduction (Ikuta et al. 2001). In the case of sockeye salmon, weak acidic conditions of <pH 6 were enough to depress the prespawning behavior of swimming upstream (Ikuta et al. 2001).

It should be noted that chemical treatment will often lead to non-target kills, and so all options for management of a species should be adequately studied before a decision is made to use piscicides or other chemicals. Potential effects on non-target organisms, such as macroinvertebrates and other fishes, should always be deliberately evaluated and analyzed. Other non-selective alterations of water quality, such as reducing dissolved oxygen levels or altering pH, could also have a deleterious impact on native fish, invertebrates, and other fauna, and their potential harmful effects should therefore be evaluated thoroughly.

Note: Check state/provincial and local regulations for the most up-to-date information regarding permits for control methods. Follow all label instructions.

The addition of sockeye into the Great Lakes ecosystem was intended primarily to occupy the gap left by failing planktivorous fish populations and secondarily to function as a forage fish (Collins 1978). The two common names of O. nerka, "sockeye" and "kokanee" refer to anadromous and non-anadromous forms, respectively. In many cases populations of kokanee are more closely related to populations of sockeye that spawn downstream than they are to populations of kokanee in other geographic locations (Taylor et al. 1996).