Pighead prickleback COSEWIC assessment and status report: chapter 5

Habitat

Habitat requirements

Pighead pricklebacks are found at various depths and salinities. In Japanese waters, they are found in coastal lakes and shallower seas near estuaries although they have also been recorded at a 60-70m depth in the ocean (collection NMC 84-0232 – Table 1); in Alaskan waters, they are found at the mouth of Egegik River (Bristol Bay, Bering Sea), as well as in the ocean near Adak (Aleutian Islands) and at depths of up to 56 m in Bristol Bay (Mecklenburg 1994ms, 2002).

Table 1. Seasonal distribution of capture for museum collections
Location 14-21 June 21-30 June 1-7 July 8-14 July 15-21 July 21-30 July 1-7 August 8-14 August 15-21 August 21-31 August 1-7 Sept.
Phillips Bay - - - 1 - - - - - - -
Kugmallit Bay - - - 1 1 - - 1 1 - 1
Tuk. Harbour 2 - - 11 - - - - 23 - -
Hutchison Bay - - - - - - - 1 - - -
Liverpool Bay - - - - - 5 7 272 6 1 4
Total 2 0 0 12 1 5 7 272 30 1 4

In Canada, most information about pighead pricklebacks is known from Tuktoyaktuk Harbour (located in Kugmallit Bay, Beaufort Sea, east of the Mackenzie Delta). The maximum depth of capture in this location was 26 m (Hopky and Ratynski 1983). They are mostly known in or below the halocline, in areas where salinity gradients range from 1% (parts per thousand) above to 30% below the halocline during winter, and 12% above to 27.5% below the halocline in summer (Galbraith and Hunter 1976; Hopky and Ratynski 1983). Inshore salinity increases in late summer to early spring, allowing increased access of pricklebacks into shallower waters. Tidal amplitudes are insignificant here compared to most Canadian marine waters. Winter temperatures range between 0°C under ice cover and 0.5°C on the bottom of the harbour. In summer, temperatures can be 15°C on the surface and 0°C on the bottom.

New ice usually forms in October with relatively smooth landfast ice occupying the inshore region over the 20-m isobath, some of the ice remaining in place throughout winter (McDonald et al. 1995). Nearshore waters less than 2 m freeze to the bottom. Depending on ice thickness, the oceanic halocline is variably restricted by narrowed shallow entrances to Tuktoyaktuk Harbour. During spring, dilute waters of the Mackenzie pass through these entrances, replacing surface layers, likely causing pighead pricklebacks to seek deeper habitat within the harbour. Other known populations have free access to oceanic habitats [see charts 7608, 7661, 7662, 7663, 7664, 7685 Canadian Hydrographic Service (2001)]. Most inshore water is <10 m for 6 to 15 nautical miles off the Mackenzie delta; however, no pighead pricklebacks are known between Kugmallit Bay off the eastern Mackenzie Delta to Phillips Bay, Yukon Territory.

Habitat trends

There are no data on habitat trends.

Habitat protection/ownership

The gederal government controls much of the Beaufort sea-bottom where pighead pricklebacks occur. Federal and territorial authorities are responsible to manage fisheries and ensure environmentally safe water standards. Surface and subsurface resources in Tuktoyaktuk and Hutchison harbours are owned and controlled by the Inuvialuit people. In Liverpool Bay, the Inuvialuit control surface resources, but not subsurface oil or mining resources (Indian and Northern Affairs Canada, 2002). Accordingly, protection of habitats occupied by pighead pricklebacks requires cooperation among all interested parties. 

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