The relationships between anadromy, sex ratio and parr growth of Arctic charr in a lake in North Norway

Abstract

Relationships between the degree of anadromy, sex ratio and parr growth of Arctic charr Salvelinus alpinus were investigated in Lake Storvatn in Hammerfest town, by estimating the densities of resident and anadromous charr in the lake, and by comparing the smolt characteristics of fish captured in the outlet river with those of fish of the same age in the lake. About two‐thirds of the charr older than 5 years were anadromous. The sex ratio of smolts was approximately 1 : 1 and the frequency of mature male parr in the lake was low. As females tended to dominate the mature portion of the anadromous population, there was probably a relatively higher mortality among sea‐run male smolts. The youngest smolts (3+ and 4+) were probably recruited from fast‐growing parr in the littoral zone, while older smolts (>4+) may have been recruited from all habitats in the lake.

Effects of the sea louse Lepeophtheirus salmonis on temporal changes in cortisol, sex steroids, growth and reproductive investment in Arctic charr Salvelinus alpinus

“…For example, in the wild, K of descending S. alpinus of the Hammerfest strain is c . 0·7 (Rikardsen et al , 1997; Rikardsen & Elliott, 2000), which is actually slightly below the condition in not re‐maturing females in the present study. Sea‐lice infection in the wild may therefore elicit a larger reduction in maturing fish, or there may be a reduction in maturation to lower infection intensities, than seen in this study.…”

“…On 23 June, two of the groups were infected with either a medium or a high dose of sea‐lice copepodids, and all groups were then maintained in sea water for 34 days (27 July) which approximate the length of a natural sea migration of this strain of S. alpinus (Jobling et al , 1998). When kept in sea water, temperature increased slowly from 6·6 to 8·1° C. In June, wild fish of this strain of S. alpinus migrate to sea (Rikardsen et al , 1997) and no mortality was recorded after transfer. After residence in sea water (on 27 July), fish were transferred, during a 3 day period, back to fresh water at ambient temperature (10·2° C).…”

Migrate or stay: terrestrial primary productivity and climate drive anadromy in Arctic char

“…In addition, increased lake water temperatures should increase the probability of migration by affecting fish growth. Although counterintuitive at first, it has repeatedly been shown that within populations, migrating individuals of Arctic char have faster growth in freshwater than resident individuals, even before the first migration (Kristoffersen et al ., ; Rikardsen et al ., , ; Rikardsen & Elliott, ). This is likely linked to size thresholds associated with migration.…”

Maternal genetic effects on adaptive divergence between anadromous and resident brook charr during early life history

“…Although anadromy appears to delimit this reproductive investment (Kinnison et al ., 2001; Kinnison et al ., 2003; Hendry et al ., 2004b), relative embryo and yolk sac size in the progeny of our anadromous dams were higher than that of female residents. Higher investment by anadromous individuals might represent an overcompensation for saline mortality in order to offset costs of marine migration and/or predation in transit to the spawning site, while residents adopt a more cautious tactic for reproductive investment (see Crespi & Teo, 2002) given lower instantaneous mortality rates (Rikardsen et al ., 1997).…”