Littoral spawning habitats of three southern Arctic charr (Salvelinus alpinus L.) populations

Abstract

Arctic charr populations in southern latitudes are nonmigratory, with all life‐stages limited to freshwater lakes and in‐ or out‐flowing tributaries. Although many of these populations are reported to also spawn in lake littorals, little is known about the physical characteristics of putative spawning grounds. A total of 23 discrete spawning sites within three Irish lakes were located by fyke netting of spawning adults and snorkelling in littoral habitats. Spawning sites were found to be long, narrow strips running parallel to the shore at a maximum depth of 124 cm. Spawning sites were limited to areas of coarse mineral substrate with an adequate (c. 8 cm) depth of clean interstitial spaces. In individual lakes, combined areas of spawning sites made up 0.4–0.7% of available littoral. Egg densities varied considerably between sites (33–900·eggs m−2) and were significantly correlated with gradient and width of spawning sites. No evidence of redd digging was found. The shallow, localised and restricted nature of spawning grounds makes such populations vulnerable to anthropogenically induced postoviposition changes in surface water level, eutrophication processes such as increased lake sedimentation and elevated nutrient status.

Distribution, characteristics and condition of Arctic charr (Salvelinus alpinus) spawning grounds in a differentially eutrophicated twin‐basin lake

“…As noted by Maitland (1995), Igoe et al (2003), Maitland et al (2007), Low et al (2011) and many others, increased algal production generated by eutrophication frequently manifests itself as increased fine sediments of algal origin deposited on stones, gravels and other substrates. As noted by Maitland (1995), Igoe et al (2003), Maitland et al (2007), Low et al (2011) and many others, increased algal production generated by eutrophication frequently manifests itself as increased fine sediments of algal origin deposited on stones, gravels and other substrates.…”

“…Recently, Low et al (2011) have partially addressed this lack of information for lacustrine lithophilic spawners by describing the littoral spawning habitats of the holarctic Arctic charr in three lakes in Ireland. Using a combination of fyke netting and snorkelling, the physical characteristics of 23 discrete spawning sites were described as narrow strips of hard substrates with clean interstitial spaces running parallel to the shore at a maximum depth of 1.2 m. The lacustrine spawning ecology of Arctic charr populations is further complicated by the fact that although many populations spawn in the littoral zone, some spawn at greater depths (Klemetsen et al 2003).…”

“…In particular, eutrophication has the potential to produce major impacts on littoral spawning fish due to associated increases in fine sediments of algal origin deposited on stones, gravels and other substrates (Winfield 2004). In the face of this lack of fundamental knowledge and widespread conservation concerns, Low et al (2011) understandably called for long-term monitoring and comparisons of Arctic charr spawning site habitats amongst lakes of differing conditions such as nutrient loading. In the face of this lack of fundamental knowledge and widespread conservation concerns, Low et al (2011) understandably called for long-term monitoring and comparisons of Arctic charr spawning site habitats amongst lakes of differing conditions such as nutrient loading.…”

Hydroacoustic quantification and assessment of spawning grounds of a lake salmonid in a eutrophicated water body

“…Such postulated temporal changes cannot be addressed in detail due to a lack of historical data, but the failure of the present survey to detect suitable spawning conditions at depth at Holbeck Point despite earlier direct observations of such by divers up to the mid-1960s reported by Frost (1965) suggests that local sedimentation has indeed occurred. The dangers of eutrophication-associated sedimentation have been highlighted in general terms for Arctic charr by Low et al (2011) and such impacts were concluded to have contributed to a decline of this species observed in Windermere in recent years by Miller et al (2015). Although Frost (1965) reported fish spawning on a gravel tongue at depths of between 9.8 and 28.0 m, more recent biological surveys have notably only found fish spawning at 10.0 m (Miller et al, 2015) which approximately equates to the maximum depth of hard bottom areas observed in the present study.…”

“…Lithophilic species such as members of the widespread genera Coregonus, Salmo and Salvelinus require gravel or other hard substrates for spawning and as a result may use only a fraction of the total habitat for such purposes, even within the littoral zone where erosive processes often dominate (Low et al, 2011). Furthermore, the quality of such limited spawning areas is particularly sensitive to the local deposition of fine sediments and as a result the widespread environmental problem of eutrophication has frequently led to declines in recruitment and even to the local extinction of a number of lithophilic species (e.g.…”