Aquatic Species at Risk - Paxton Lake Stickleback Species Pair (Benthic and Limnetic Forms)

Description
Habitat
Threats
How Can You Help?
Further Information
Scientific Information

Description
The Paxton Lake Sticklebacks are small, lean fish with an elongated body that tapers to a slender tail. They possess lateral plates that provide some protection against predators. Two variety of this fish – the bottom dwelling “benthic” form and open water swimming “limnetic” form, have been identified by scientists. They both evolved from a common Three Spine Stickleback ancestor in marine environment. Only 4.5 cm in length when fully mature, the limnetic form has a narrow mouth, many long gill rakers, and three dorsal spines. The benthic form is about twice as large when mature and has a wide mouth, a few short gill rakers, and fewer spines. Body color varies from silvery to mottled green and brown. 

These two distinct but closely related Sticklebacks (Benthic and Limnetic form) are commonly referred to as “Stickleback Species Pair”.

Habitat
This Stickleback Species Pair live in Paxton Lake on Texada Island, located between Vancouver Island and mainland British Columbia. Habitat requirements for both Stickleback forms include deep and shallow waters of Paxton Lake. Both parts of the lake are productive and offer food sources for these fish. The aquatic vegetation, along with lake water quality, play an important role in keeping the separation of two forms. Benthic forms build nests under the shelter of aquatic vegetation while Limnetic forms tend to build theirs in shallow, but open and unsheltered areas. Because of this nesting separation, both forms are able to breed in isolation, and little hybridizing happens between them. Invasive species can damage this delicate balance. For example, the invasion of freshwater Crayfish to Enos Lake on Vancouver Island caused the destruction of aquatic vegetation, which likely caused higher hybridization rate and loss of pure forms of Stickleback Pairs there.

To protect themselves from predators, sticklebacks congregate in areas of tall vegetation or surface cover. At night, however, they prefer the deeper and open waters of the lake.

Threats
Primary threats to the Paxton Lake Stickleback Pair include: invasive species; impacts from water extraction, and land use.

Invasive species have been responsible for the higher hybridization and collapse of a similar species pair in Enos Lake on Vancouver Island. The general consensus from scientists is that any invasive species will pose a major threat to the survival of the Stickleback Species Pairs. 

Water and land use may also have major impact to the sustainability of Paxton Lake Stickleback Species Pair, as they dictate the quality of the lake environment in terms of water level, water quality and healthy aquatic vegetations.

How Can You Help?

• Prevent invasive species from entering the environment: Many species of aquatic invasive can be transported with your boat, trailer, or fishing gear without you noticing. Once they enter the environment, these invasive species pose major risks to the delicate balance of a lake ecosystem. For more information please visit these websites:
  • Protect Your Waters.net (http://www.protectyourwaters.net/)
  • DFO Publication: STOP The spread of Invasive Species (http://www.pac.dfo-mpo.gc.ca/publications/docs/invasives-envahissantes-eng.htm)
    
    
• Respect the environment: Always put trash in trash cans, especially near rivers, lakes and beaches. Protect vegetation around lake shorelines, as it helps to prevent excessive sediments from entering into water.
   
• Record and report damage to fish habitat and pollution:
  Contact DFO’s Observe, Record and Report (ORR) phone line to report suspected environmental violation that damage fish habitat or cause pollution. (1-800-465-4336 or in Greater Vancouver: 604-607-4186)
  
  
• Participate in community consultations: Get involved in Community Working Groups or visit www.pac.dfo-mpo.gc.ca/saraconsultations
  
  
• Volunteer: This may include participating on committees, attending meetings, assisting at educational outreach events, distributing outreach materials, getting involved with a conservation organization, like the Texada Stickleback Group, or just simply telling a neighbour or a friend about this species.

The Paxton Lake Stickleback Species Pair will get the protection they need only if all Canadians work together to reduce threats. Find out more on how to best reduce these threats wherever possible, to better protect these species at risk and their habitat. For general information on conservation efforts, visit Habitat Stewardship Program for Species at Risk.

Further Information:
Benthic forms differ from Limnetic Forms in a number of ways: they generally mature later, live longer and reproduce less often. Limnetic Forms generally die after two years while Benthic forms can perhaps live as long as 7 years.

As adults, the Species Pair’s diet is also significantly different; limnetics hunt primarily in the surface waters away from the lake shores for plankton, while benthics forage along the shallow margins of the lake for larger prey such as snails, dragonfly nymphs, amphipods, and chironomids. In the spring, sticklebacks build nests in the part of the lake closest to the shore, sometimes mating with several females. Following fertilization eggs usually take 7-10 days to hatch. Male sticklebacks are particularly territorial and protective of their young.

In 2005, a population survey on the Paxton Sticklebacks was conducted using mark-recapture technique. The results show that the total stickleback population to be about 6,600 for the Benthic form and 91,706 for the Limnetic form.

A recovery strategy has been developed by Fisheries and Oceans Canada and the Province of British Columbia. The next step is development of an action plan to outline the measures required to meet the goals and objectives of the recovery strategy.

Scientific Information:

Scientific Name: Gasterosteus sp.
Taxonomy: Fishes (freshwater)