king salmon

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

Environmental	Beneficial

Oncorhynchus tshawytscha has a high environmental impact in the Great Lakes.

Realized:
In the Great Lakes, O. tshawytscha competes with native lake trout (Salvelinus namaycush) (Page and Laird 1993). Scott et al. (2003) found that the presence of O. tshawytscha causes delayed nesting and reduced survival of Atlantic salmon (Salmo salar) during spawning in Lake Ontario. Additionally, Atlantic salmon was generally more active and males engaged in more agonistic behavior (head-down, lateral display, parallel swim) when O. tshawytscha was present. Such effects could have a negative impact on present Atlantic salmon restoration efforts.

The introduction of Pacific salmonines is deemed responsible for the introduction of Renibacterium salmoninarum, which causes bacterial kidney disease in lake trout, brook trout (S. fontinalis), lake whitefish (Coregonus clupeaformis), and bloater (C. hoyi). However, the specific role of O. tshawytscha in this introduction is unknown (see GLANSIS fact sheet for R. salmoninarum).

Crawford et al. (2001) pointed out that salmonids have the potential to alter the energy and nutrient cycles of the Great Lakes system through increased energy transfer between open water and streams/tributaries. This energy transfer includes the addition of nitrogen and phosphorus to tributaries through decaying salmonine carcasses, as well as the addition of salmon eggs and dead fish as a food source in streams (Ivan et al. 2011, Parmenter and Lamarra 1991, Rand et al. 1992). Rand et al. (1992) found that phosphorus released from salmon carcasses was responsible for >50% of the total phosphorus discharged in some Lake Ontario streams during parts of the spring. The presence of live salmonids may have an even greater effect on nutrients in streams through the excretion of ammonium and soluable reactive phosphorus and their mechanical disturbance of the stream bottom during spawning runs (Ivan et al. 2011, Tiegs et al. 2009). In Lake Ontario, O. tshawytscha is being parasitized by the copepod Salmincola califorensis (Mullin and Reyda 2020).

Potential:
O. tshawytscha is a predatory fish and may impact populations of smaller fishes. Some agencies in lakes Michigan and Ontario drastically reduced their stocking quotas for chinook salmon in the 1990s and are concerned about their impact on the fish community, namely declining populations of alewife (Alosa pseudoharengus) and other forage fish (Schreiner 1995). Jones (1993) predicted that maintaining high levels of predator demand by stocking O. tshawytscha and other top predators at the current rate would eventually lead to an alewife collapse, possibly followed by the further collapse of other small forage fish populations. O. tshawytscha had totally eliminated rainbow smelt (Osmerus mordax) in two small New Hampshire lakes where the salmon was stocked to control the smelt (McAffee 1966).

Negus (1995) proposed that stocking of O. tshawytscha in Lake Superior could be modified to alter predation pressure on important prey species. However, hatchery-reared O. tshawytscha was found to make up only 25% of the sport fish catch in Lake Superior—such lack of predominance indicating that O. tshawytscha have become naturalized and stocking efforts may only marginally affect Chinook salmon biomass in the lake (Peck 1999). Hatchery-reared O. tshawytscha in Lake Huron only contributes 1 out of every 8 fish in the population (MIDNRE 2011).

There is little evidence to support that Oncorhynchus tshawytscha has significant socio-economic impacts in the Great Lakes.

As this species is intentionally stocked for recreation, there are no negative impacts on human health or recreation associated with this species.

Oncorhynchus tshawytscha has a high beneficial effect in the Great Lakes.

Realized:
Since the introduction of O. tshawytscha to control alewife populations in the 1960s, O. tshawytscha has remained an important component of the Great Lakes fisheries and is recreationally and economically valuable. It was estimated that of the five most-stocked non-native salmonine species (O. kisutch, O. mykiss, O. tshawytscha, S. trutta, S. salar), O. tshawytscha constituted 45% of all stockings before 1998 (Crawford 2001). It is most commonly fished in open water, but is also fished as a fall stream species (especially off of Lake Ontario) (Bence and Smith 1999). From 1967 to 1993, over 259 million individuals were stocked in the Great Lakes (Kocik and Jones 1999). In 2005, nearly 9.5 million chinook salmon were stocked in the Great Lakes system (not including Lake Erie) as reported by various agencies (USFWS/GLFC 2010). Most were stocked in Lake Michigan (4,000,000+) followed by Lake Huron (2,500,000+) (USFWS/GLFC 2010). A 2005 survey of anglers fishing in Canada reported an annual recreational harvest of 426,890 individuals in the Great Lakes system (Fisheries and Oceans Canada 2008). Additionally, chinook salmon is a significant catch of the Native American commercial harvest, especially in Lake Huron (Bence and Smith 1999).

Potential:
Eggs spawned by O. tshawytscha have been found to comprise an important part of the native brown trout diet in Great Lakes tributaries, but the effects of this consumption have yet to be understood (Ivan et al. 2011; Hermann et al. 2020). O. tshawytscha is currently being evaluated as a pollutant indicator in the Great Lakes (Renaguli et al. 2020).

Pacific salmon management is extremely diverse, integrated, and cascading and is therefore these are the most heavily regulated species (direct and indirectly) in the Great Lakes. Great Lakes states and provinces have their own specific fishing regulations. Generally, the overall goals and objectives of Pacific salmon fishing regulations are the same throughout the region i.e., to maintain or enhance a healthy and sustainable salmonid fisheries. Pacific salmon fishing regulations include daily and season bag limits, size limits, permitted baitfish, manner of taking i.e., snagging or hook and line, and designated season dates (See New York DEC, Pennsylvania F&BC, Ohio DNR, Michigan DNR, Indiana DNR, Illinois DNR, Minnesota DNR, Wisconsin DNR, Ontario MNR, and Quebec MRNF websites for specific fishing regulations). 

Typically, Pacific salmon regulations are not species specific, but rather regulate the salmonid fisheries as a whole. Indirect Pacific salmon regulations include mandated salmonid pathogen screening tests and baitfish regulations.
Mandatory salmonid pathogen screening tests are implemented in all Great Lakes states and provinces. The importation, exportation, and transportation of Pacific salmon is highly regulated to control the spread of infectious diseases and parasites such as VHS, BKD, and whirling disease (See USGS nonindigenous diseases and parasites fact sheets for state and provincial regulations).
State and provincial baitfish regulations have aided in preventing the spread of infectious disease. Specific and or stricter regulations are placed on baitfish species that are known carriers of salmonid pathogens.

Note: Check federal, state/provincial, and local regulations for the most up-to-date information.
Control
Biological
Pacific salmon prey heavily upon two non-native species in the Great Lakes, the alewife (Alosa pseudoharengus) and rainbow smelt (Osmerus mordax).   Alewives remain a key food source and crucial to the survival of Pacific salmon.  Over the past several decades, Pacific salmon populations have fluctuated with fluctuating alewife populations. Managing one species significantly impacts the other. Pacific salmon and alewives have significant environmental, socio-economic, and beneficial effects in the Great Lakes and therefore integrated management is essential. Rainbow smelt are also a major component of Pacific salmon diet. Similar to alewives, Pacific salmon and rainbow smelt management should be integrated.  Rainbow smelt have a high environmental impact and high beneficial effect in the Great Lakes. The presence or absence of this species significantly alters predator-prey relationships and competition between native species. Managers can also attempt to increase less harmful native prey species stocks while allowing harmful invasive prey species to decrease.  Implementation of this bio-control has potential significant beneficial effects in the Great Lakes with few negative impacts (See USGS fact sheets on alewife and rainbow smelt).

Of the 23 nonindigenous diseases and parasites in the Great Lakes, Aeromonas salmonicida, Renibacterium salmoninarum, Myxobolus cerebralis, and Novirhabdovirus sp. infections have been realized in Great Lakes Pacific salmon, while Heterosporosis sp. and Piscirickettsia cf. salmonis infections have been realized clinically or outside the Great Lakes. Glugea hertwigi, a microsporidian, is known to cause mortality in rainbow smelt. Therefore, Pacific salmon management must include the management of the above pathogens and parasites (See USGS fact sheets on Aeromonas salmonicida, Renibacterium salmoninarum, Myxobolus cerebralis, Novirhabdovirus sp., Heterosporosis sp., Piscirickettsia cf. salmonis, and Glugea hertwigi for information on Great Lakes impacts and management).

Physical
Aquaculture facilities manage wild and cultured Pacific salmon stocks through wild stock assessments and other methods. Managers are then able to make informed decisions on stocking strategies. Research, pathogen screening, and pathogen treatment, etc. is conducted in aquaculture facilities (See state and provincial DEC, MNR, DNR, and corresponding agency and department websites for information on salmonid aquaculture and state hatcheries).

Chemical
Chemical controls for Pacific salmon are not intended to eradicate or kill the species but rather to protect it against infectious disease. Typically, depending on the target species, chemicals controls are only effective in aquaculture or similar systems. Examples of chemicals used and include Furogen®, chlorination, and disinfectants.

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