Anadromous Charr Research Articles

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

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.

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

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.

Genetic relationships among populations of wild resident, and wild and hatchery anadromous brook charr

Genetic relationships among populations of wild resident, and wild and hatchery anadromous brook charr

Evidence for Non-Anadromous Behaviour of Arctic Charr (<i>Salvelinus alpinus</i>) from Lake Hazen, Ellesmere Island, Northwest Territories, Canada, Based on Scanning Proton Microprobe Analysis of Otolith Strontium Distribution

Scanning proton microprobe analysis was used to determine the distribution of strontium (Sr) in otoliths from arctic charr (Salvelinus alpinus) of known non-anadromous, known anadromous, and unknown life histories. Strontium concentration patterns in otoliths of known non-anadromous charr were low and relatively flat (with little variation) from the core area to the outermost edge of the otolith, while patterns for known anadromous charr were characterized by a similar low, flat region for the first several years of life, followed by marked oscillatory increases and decreases in Sr content for the duration of the fish's life. Small and large forms of Lake Hazen charr of unknown life histories exhibited Sr profiles that were similar to those of the known non-anadromous charr, which strongly suggest that Lake Hazen charr are non-anadromous. These results indicate that Lake Hazen is a "closed" system with energy cycling primarily within the system; this conclusion suggests that a conservative approach would be appropriate for the management of the Lake Hazen charr population.

Differences in susceptibility of anadromous and resident stocks of Arctic charr to infections of Gyrodactylus salaris, under experimental conditions

The ability of Gyrodactylus salaris, an important pathogen of the Atlantic salmon Salmo salar, in Norway, to infect anadromous and resident stocks of the Arctic charr, Salvelinus alpinus, has been examined in the laboratory. Resident charr (Korssjoen stock) exposed to heavily infected salmon, were considered innately resistant as they lost their infections within 21 days when individually isolated. Isolated anadromous harr (Hammerfest stock) remained infected for up to 150 days, although most infections disappeared within 30–50 days. In many cases the parasite population grew initially, but growth was limited after 20–30 days and infections subsequently disappeared. At the same time, shoals of 50 anadromous charr, swimming in the tanks containing the individually isolated fish in floating cages, remained infected for up to 280 days. Charr isolated from these shoals after 115 days and subsequently monitored individually lost their infections within 30 days, although the parasite persisted within the shoals for a further 75–135 days. This suggests that G. salaris, persisted on shoaling charr despite an immune response which led to the elimination of parasites from isolated hosts. The Hammerfest stock of anadromous charr supports G. salaris, in the laboratory, and the extended period of survival on this host suggests that charr may be important in the epidemiology of G. salaris, in northern Norway.

Smolt characteristics of small first-time migrant, and resident Arctic charr, Salvelinus alpinus (L.), from a river system in northern Norway

Smolt characteristics were investigated in sympatric anadromous and resident Arctic charr. Salvelinus alpinus (L.), of a similar size (11-20 cm), A group of first-time migrant anadromous charr was caught while descending the Hals River and two groups of resident conspecifics were caught in Lake Storvatn. one before, and one after, the sea-run of anadromous fish had terminated. When sampled immediately after capture in fresh water the anadromous group had a higher proportion of fish visually classified as smolts. and these charr had higher gill Na+-K+ ATPase activity, higher densities of developed chloride cells in the gills, a lower condition factor, and lower plasma osmolality, than resident fish. When exposed to sea water (33%o S), only minor differences in mortality and plasma electrolyte levels were observed between anadromous and resident fish, average values of plasma osmolality and chloride concentrations being 377 mOsm and 169 mM and 387 mOsm and 174 mM, respectively. The results suggest that the first-time migrant Arctic charr had undergone some of the physiological changes that are considered typical for a parr-smolt transformation before they left fresh water. Such changes did not appear to have occurred in sympatric, resident, fish of a similar size. The parr-smolt transformation in the first-time migrants may, however, have been incomplete, because the fish did not appear to have the ability to rapidly re-establish osmo- and ionoregutatory homeostasis after direct transfer to sea water.

Migration, growth and survival of wild and hatchery‐reared anadromous Arctic charr (Salvelinus alpinus) in Finnmark, Northern Norway

Two groups of anadromous Arctic charr (Salvelinus alpinus) (size 200–350 mm) reared in heated water (6–12° C) under simulated natural photoperiod were individually tagged and released in spring 1988. The fish were released at two sites, in the estuary of the River Halselva and in the fjord, 2 km from the river mouth. Growth, timing of migration and survival of these hatchery‐reared fish was compared to that of wild anadromous charr of the same size over a 4‐year period. The hatchery‐reared charr had poorer growth than the wild fish during their first year in sea water. They also resided longer in the sea and had a slightly lower survival than wild fish. During the second year, hatchery‐reared charr displayed good growth, and after the third sea‐season the fish were ready for slaughter at a size of approximately 800g. The results suggest that the successful development of Arctic charr ranching will be dependent upon production and release strategies that lead to improved migratory and feeding behaviour of the fish during their first season at sea.

Characteristics of carotenoid features in muscle and ovary from anadromous and river resident types of Alaskan dolly varden charr ( Salvelinus malma malma)

1. 1. The carotenoids in the muscles and eggs from two types of natural Alaskan dolly varden charr, anadromous and river resident types, were examined. 2. 2. In the muscle from the anadromous charr, astaxanthin was the major component comprising more than 70% of the total, followed by idoxanthin and 4-keto-zeaxanthin. 3. 3. The egg carotenoid features in the river resident charr were more complicated compared with those in the anadromous fish. A considerable proportion of unidentified carotenoids was found in the eggs from the river resident charr. 4. 4. Idoxanthin was the main component along with considerable propotions of β-carotene tetrol and astaxanthin in the eggs from the anadromous charr, whereas zeaxanthin and lutein were detected besides idoxanthin and β-carotene tetrol in the eggs from the river resident fish. 5. 5. The prey was considered to be responsible for the difference in the carotenoid features of the eggs from the anadromous and river resident charr.

Metazoan parasite infections in landlocked and anadromous Arctic charr (Salvelinus alpinus Linnaeus), and their use as indicators of movement to sea in young anadromous charr

Eighteen genera of metazoan parasites (Monogenea, 1; Digenea, 7; Cestoda, 4; Nematoda, 4; Acanthocephala, 1; Copepoda, 1) were collected from 172 landlocked and anadromous Arctic charr (Salvelinus alpinus Linnaeus) in northern Labrador. Four species (Lecithaster gibbosus, Diphyllobothrium dendriticum, Diphyllobothrium ditremum, and Salmincola carpionis) and one genus (Tetraonchus) have not previously been reported from Arctic charr in Labrador. The dominant parasites in the landlocked charr were Diplostomum sp., Crepidostomum farionis, and Diphyllobothrium ditremum. In the sea-run charr, Bothrimonus sturionis and Brachyphallus crenatus were dominant. Regression analyses indicated that the numbers of parasites were significantly correlated with host age (P < 0.001) for these species. All landlocked charr sampled were infected with parasites by age 1+ years whereas all sea-run charr were infected by age 3+. At 1+ years, 43% of the Arctic charr collected in the Ikarut River were infected with marine or brackish-water parasites, suggesting that some young charr, not yet ready for the annual seaward migration, may make short feeding excursions into salt water.

Potential use of certain parasites of brook charr (Salvelinus fontinalis) as biological indicators in the Tabusintac River, New Brunswick, Canada

A survey of 1146 nonanadromous and anadromous brook charr (Salvelinus fontinalis) from the Tabusintac River for parasites revealed 36 species of parasites, of which 18 were freshwater and 18 were marine. Most freshwater parasites were either too common or too rare in their occurrence to be of any value as biological indicators; however, Diplostomum sp. (metacercariae), Truttaedacnitis truttae, and Salmincola edwardsii were useful as indicators of foci of infection in fresh water. Decreases in prevalences of infection with marine gastrointestinal parasites in the estuary, especially Brachyphallus crenatus, Neoechinorhynchus sp., and larvae of Hysterothylacium aduncum, provided evidence for the approximate times of arrival of anadromous charr from fresh water. Marine gastrointestinal parasites were also useful as biological indicators of anadromous charr in fresh water, but these parasites were lost after varying times. High prevalences of infection with metacercariae of the marine digenean Cryptocotyle lingua resulted in a black spot condition that proved to be the best indicator of anadromous charr in fresh water. The distributions of Azygia longa, Echinorhynchus lateralis, and Zoogonus lasius from charr in the Tabusintac River as well as the nearby Miramichi and Burnt Church estuaries suggested that estuarine wanderings among adjacent river systems do occur. Tetraphyllidea gen. sp. plerocercoids from anadromous charr in the Tabusintac River were useful in identifying offshore movements of these charr into the Gulf of St. Lawrence.

Diplostomiasis (Trematoda: Strigeidae) in Arctic charr (Salvelinus alpinus) from Charr Lake, northern Labrador.

The eyes of 273 Arctic charr (Salvelinus alpinus) taken from Charr Lake, the Ikarut River, and Hebron Fiord in northern Labrador were examined for diplostomula. All anadromous charr taken from the Ikarut river and Hebron Fiord were uninfected. The resident fish from Charr Lake were parasitized with large numbers of diplostomula and intensity of infection increased with age and length. Infections of up to 2,852 diplostomula in one fish are the highest recorded. Such infections did not appear to affect the vision of the charr.

A survey of the parasites of nonanadromous and anadromous brook charr (Salvelinus fontinalis) in the Tabusintac River, New Brunswick, Canada

A parasite survey of 1146 brook charr (Salvelinus fontinalis) was conducted between January 1981 and December 1982 in the Tabusintac River, New Brunswick, Canada. A total of 36 parasite species were recovered, of which 18 (one Myxosporea, two Monogenea, three Digenea, three Cestoidea, five Nematoda, one Acanthocephala, one Hirudinoidea, one Crustacea, and a Dermocystidium sp.) were freshwater and 18 (two Monogenea, seven Digenea, two Cestoidea, two Nematoda, two Acanthocephala, and three Crustacea) were marine. Anadronomous charr were differentiated from nonanadromous charr in fresh water by the presence of marine parasites. Charr in the estuary and lagoon were all considered to be anadromous; however, first-time anadromous charr or smolts were differentiated by the absence of marine parasites and infection with freshwater parasites only. New host records include Lecithaster gibbosus, Zoogonus lasius, Podocotyle angulata, Cryptocotyle lingua (metacercariae), Stephanostomum tenue (metacercariae, adults), Eubothrium crassum, Tetraphyllidea gen. sp. (plerocercoids), Eustrongylides sp. (larvae), Hysterothylacium aduncum (larvae, adults), Corynosoma magdaleni (juveniles), Argulus alosae, and Ergasilus labracis. Zoogonus lasius and Stephanostomum tenue represent new Canadian records, and Chloromyxum truttae and Truttaedacnitis truttae are reported for the first time from New Brunswick. Bulbodacnitis alpinus, previously reported only from the Arctic charr (Salvelinus alpinus), is considered to be a synonym of T. truttae.

Salmon and freshwater fishes of the Inner Hebrides

SynopsisApart from limited studies on salmon and sea trout no previous investigation of the status and distribution of Inner Hebridean freshwater fishes has been made. Only euryhaline fishes were able to recolonise Hebridean freshwaters after the last glaciation. Thus seven indigenous, freshwater fishes have been recorded in the Inner Hebrides: Atlantic salmon, trout, Arctic charr, three- and ten-spined stickleback, European eel and brook lamprey. Trout occur both as anadromous and sedentary forms but charr as the sedentary form only.Flounders penetrate far upstream and may be found in lochs while grey mullet occur seasonally in streams a short way inland from the sea. In contrast to the Outer Hebrides there are established populations of non-indigenous species; American brook charr occur in lochs only on Eigg and Mull and pike and perch only on Islay.Populations of rainbow trout are artificially maintained. On some small islands, freshwater bodies are temporary so that there are no permanent fish populations while on others, where freshwaters are present as ditches and small streams, only eels can exist. A survey showed that freshwater eels were the most widely distributed fish, followed by trout and three-spined stickleback in that order.Salmon and sea trout are found in all the major river systems and are also caught in nets on the coasts of the larger islands. These coastal fisheries also exploit salmon in passage to river systems elsewhere in Scotland.

Life history and movements of anadromous brook charr, Salvelinus fontinalis, in the St-Jean River, Gaspé, Quebec

A comparison between an anadromous and a freshwater lake population of brook charr showed that anadromous charr had a lower mean length at age 2+ and 3+, a greater longevity, a greater maximal length and a greater length and age at first maturity than the freshwater population. A biased sex ratio towards females occurred only in the anadromous population. The first 2 or 3 years in the life cycle of anadromous charr is spent in the river, followed by an intermediate period of a year in the salt wedge area and then by a 2- or 3-month period in salt water before returning to the river. Bigger charr started upstream migration earlier in the season than smaller charr. Migration peaks in 1979 were synchronized with the new moon. Fish movements in the estuary were greater during spring tides than neap tides. Diel activity was highest in the day in the estuary whereas the inverse situation occurred in the river. From tags returns, it was concluded that anadromous brook charr had a strong homing tendency.

Répartition des ressources et changements saisonniers de l'alimentation d'ombles de fontaine anadromes, Salvelinus fontinalis

Resource partitioning among anadromous brook charr in an estuary included habitat and prey-type partitioning. In spring and summer, juveniles were foraging in the upper estuary on crustacea and insects while adults were eating crustacea and fish in the lower estuary. In the fall, adult charr, which were all in the river, ate little. During winter, adult charr were found in the estuary and consumed crustacea and only a few fish. The relative weights of stomach contents were similar in summer and winter, showing for the first time the importance of winter feeding for this species.

Reproductive Strategy of Dwarf and Normal Arctic Charr (Salvelinus alpinus) from Vangsvatnet Lake, Western Norway

In this paper, we investigate the reproductive strategy maintaining dwarf and normal phenotypes of an Arctic charr (Salvelinus alpinus) population. Both morphs occurred together in the spawning area, but the peak abundance of dwarf spawners was significantly deeper, and later in the spawning period, than normal spawners. Both phenotypes attained sexual maturity at the same age and did not differ in length-specific fecundity or egg diameter. Our data support the hypothesis that the females matured sexually at the age that maximizes their fitness within the constraints imposed by growth and survival. The two female morphs appeared not to have equal fitness; these differences may be due to random events. The males were more heterogeneous by size than the females when maturing sexually. This may be due to intrasexual competition between males making large males the principal spawners. The dwarf males may circumvent the effects of intrasexual competition by mimicking immature fish, sneak at the redds of normal females, and participate in the spawning acts of normal charr pairs. Also, they may fertilize the eggs of dwarf females spawning in deeper areas.The two charr morphs developed from a uniform young phenotype (parr). The dwarf spawners were precocious individuals maturing sexually in their parr stage, whereas normal spawners had a color shift, analogous to smoltification in anadromous charr, before they attained sexual maturity. The different spawning coloration of the two morphs may be due to sexual selection.Key words: spawning, growth, fecundity, mortality, sexual selection, maturing strategy

Metazoan parasites as indicators of movements of anadromous brook charr (Salvelinus fontinalis) to sea

Changes in the numbers of metazoan parasites of anadromous brook charr, Salvelinus fontinalis, during the summer 1980 were determined by examining 220 fish at different times and localities in the Moisie River, Quebec. The marine trematode Brachyphallus crenatus remained in brook charr during their movements into fresh water. Differences in the prevalence of this parasite between sampling localities in late July indicated that some charr which undergo smoltification do not go to sea although others do. Also, infection with B. crenatus enabled an estimate to be made of the percentage of charr that had been to sea entering a tributary in late August. Brook charr were also infected with Crepidostomum cooperi, Diplostomum spathaceum, Eubothrium salvelini, Proteocephalus sp., Metechinorhynchus lateralis, Echinorhynchus gadi complex, Cystidicoloides tenuissima, Hysterothylacium sp., Anisakis simplex, Acuarioidea: Seuratiinae gen. sp., Salmincola edwardsii, and glochidia larvae.