The Arctic Charr in Ireland

Arctic charr is a rare and threatened species and is listed in the Irish Red Data Book for fish as vulnerable (King et al, 2011). Arctic charr populations in Britain and Ireland complete their life cycle in freshwater, although they originated from anadromous colonisers around 10,000 years ago, following the retreat of the Pleistocene Ice Cap (Maitland, 1974). Ireland’s Arctic charr populations are under major threat and approximately one-third of known populations are now extinct in Ireland (Igoe et al, 2003).

Male Arctic Charr (top) and Brown Trout from Glenicmurrin Lough, Co Galway.

Compared with Ireland’s other native salmonids, Brown/Sea trout Salmo trutta and Atlantic salmon Salmo salar, relatively little is known about the spawning habits and behaviour of Arctic charr (Igoe & Hammar, 2004; Low et al, 2011). However it is clear that in the British Isles, the majority of charr populations spawn in lakes. Indeed, of the 258 native populations documented in Scotland, only 10 populations are known to spawn in rivers, two of which are now extinct (Low et al, 2011). Furthermore, of Ireland’s 74 documented charr populations there is only a single anecdotal account of lotic (running water) spawning in a lake in the Lee catchment, where the species is now extinct (Igoe & Hammar, 2004).

Arctic charr spawn during the period October – December period (Igoe et al, 2003); however at a location in the UK (Lake Windermere) populations are known to spawn in the autumn and in the spring (Maitland & Campbell, 1992). Igoe & Hammer (2004) reported that during a survey of Lough Talt on 18th February 2004 they observed evidence that charr had recently spawned. They concluded that this suggested that spring spawning was a possibility in Ireland. McCarthy et al (2001) reported that both Lough Eske and Lough Lough Mask charr exclusively spawned in the Autumn. Maitland and Campbell (1992) describe Arctic spawning in still or flowing water as follows ‘the female clears the bottom loose debris and excavates a redd at a selected site by turning on her side and sweeping her tail fin up and down,.. within a territory that a mature male has established and is defending’. However, Rubin & Buttiker (1992) observed that Lake Le´man charr (in Switzerland) made no attempt to cut redds, rather eggs were swept into crevices after spawning by the female undulating the tail rapidly. In Lough Eske Igoe & Hammer (2004) also reported that ova are dispersed over the substrate rather than deposited in excavated redds. No evidence of redd digging was found in a recent study of three Arctic charr lakes in County Kerry (Low et al, 2011). It is noted that for the purposes of the current report any substrate disturbance attributable to spawning salmonid fish is referred to as a “redd”.

Low et al (2001) noted that spawning sites at three lakes in County Kerry were long, narrow strips running parallel to the shore. Spawning sites were limited to areas of coarse mineral substrate with an adequate (c. 8 cm) depth of clean interstitial spaces. Maitland & Campbell (1992) note that Arctic charr spawning in lakes “takes place over gravel and stones normally in fairly shallow water near the shore or on a submerged reef”. Low et al (2001) recorded spawning at a maximum depth of 124 cm, and a mean depth of 64cm. Igoe & Hammer (2004) also noted that spawning in Lough Eske also took place in relatively shallow water (0.3-1.2m deep). McCarthy et al (2001) reported that Arctic charr on Lough Corrib (now extinct) “could formerly be observed spawning in shallow water (15-25cm depth i9n some sites) on calm November evenings”. In Lough Eske McCarthy et al (2001) noted that charr were recorded spawning at depths of between 1-3m.

In the Low et al (2011) study distance from the shoreline to spawning sites varied from 0–15.1 m with the mean of all sites being 5.7 m (N = 23) from the shore. Lough Eske charr have been recorded spawning within 10m of the shoreline according to Igoe & Hammer (2004).

Arctic charr ova are smaller than other salmonids. McCarthy et al (2001) reported that egg diameter for Lough Mask Charr ranged from 2.3 to 6.3mm (n=45 fish). The eggs from 8 Lough Eske females ranged from 2.1 to 4.7mm. Maitland a& Campbell (1992) said that Arctic charr ova are amber in colour and have a diameter of 4-5mm. Relatively few fecundity studies have been completed in relation to charr, but it is known that a 250g fish can produce 400-600 ova (Maitland & Campbell, 1992). McCarthy et al (2001) reported that the mean fecundity of L. Mask and L. Eske female charr was 1,129 yolked eggs for Lough Mask (range, 480 to 2,249) and 257 yolked eggs for Lough Eske (range 100 to 483).

Maitland and Campbell (1992) note that trout occasionally spawn in the shallow waters of lakes at the same time as charr and the evidence of trout spawning could probably be easily confused with charr spawning activity. In some charr lakes trout become piscivorous and can grow to large sizes (5kg or more). Evidence of Ferox trout spawning in littoral areas would be obvious as such fish would be likely to cut redds and such disturbances would be relatively large. It is possible that Lough Talt could also support Ferox trout. Atlantic salmon do not have access to Lough Talt.

In recent surveys of Lough Talt undertaken by the Inland Fisheries Ireland (formerly CFB), Arctic charr were recorded. In 2008 a total of 12 Arctic charr with lengths ranging from 7.5cm to 23.3cm were recorded (CFB, 2008). The lake was also surveyed in September 2011 and Arctic charr (N=18) were also recorded (IFI, 2011).

Ecofact Arctic charr survey, Lough Talt, Co Sligo

It is well appreciated that Ireland’s Arctic charr populations, which are at the southern margin of their natural range, are under major threat. Approximately one-third of known populations are now extinct in Ireland (Igoe et al, 2003). The threat is particularly apparent in Irish charr populations where the maximum age rarely exceeds 7 years (Igoe & Hammar 2004). It would therefore only take a few years of poor recruitment to put such populations at risk of being an addition to the long list of extinct southern Arctic charr populations (Igoe & Hammar 2004). According to Low et al (2001) the shallow, localised and restricted nature of Arctic charr spawning grounds makes such populations extremely vulnerable “to anthropogenically induced postoviposition changes in surface water level, eutrophication processes such as increased lake sedimentation and elevated nutrient status”.

Ecofact have extensive experience of surveying lakes for Arctic charr. We are currently undertaking assessments on Glenicmurrin lake, Co Galway and Lough Talt, Co Sligo as part of assessments for propsoed water abstraction schemes.

REFERENCES

Blanchfield, P.J. & Ridgway, M.S. (1997). Reproductive timing and use of redd sites by lake-spawning brook trout (Salvelinus fontinalis). Canadian Journal of Fisheries and Aquatic Sciences 54: 747–756.

CFB (2008) Sampling fish for the Water Framework Directive – Lakes 2008: Lough Talt. Central and Fisheries Boards.

Eshenroder, R.L., Bronte, C.R. & Peck, J.W. (1995). Comparison of lake trout-egg survival at inshore and offshore and shallow-water and deepwater sites in Lake Superior. Journal of Great Lakes Research 21: 313–322.

Frost, W. E. (1952). Predators on the ova of char in Windermere. Salmon and Trout Magazine, 136, 192-196.

Fabricius, E. & Gustafson, K.J. (1954). Further aquarium observations on the spawning behaviour of the charr, Salmo alpinus L. Report to Institute of Freshwater Research. Drottningholm 35: 58–104.

Fitzsimons, J., Jonas, J., Claramunt, R., Williston, B., Williston, G., Marsden, J., Ellrott, B. & Honeyfield, D. (2007). Influence of egg predation and physical disturbance on lake trout Salvelinus namaycush egg mortality and implications for life history theory. Journal of Fish Biology 71: 1–16.

Frost, W. E. (1952). Predators on the ova of char in Windermere. Salmon and Trout Magazine, 136, 192-196.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s