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

Helen Miller  Ian J. Winfield  Janice M. Fletcher  J. Ben James  Joey van Rijn  Jonathan M. Bull  Carol J. Cotterill 《Ecology of Freshwater Fish》2015,24(1):32-43

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Changes in the density and growth of brown trout (Salmo trutta) after intensive removal of sympatric Arctic charr (Salvelinus alpinus) in the sub‐Arctic lake Møkkelandsvatn,Norway          下载免费PDF全文

Martin A. Svenning  Øyvind K. Hanssen  J. Malcolm Elliott 《Ecology of Freshwater Fish》2015,24(4):591-599

This study tests the basic hypothesis that the removal of charr, Salvelinus alpinus (L.), would cause an increase in both the growth and density of a sympatric trout population, Salmo trutta L. The charr population was characterised by slow‐growing individuals, with a high proportion of mature fish, that is typical for so‐called overpopulated populations. A total of 31,000 charr was removed from the lake in the period 1990–1992, and the density of younger trout (1+, 2+), but not older trout (3+, 4+), increased. The growth of older trout (3+, 4+) increased, but the evidence for similar growth increases of younger trout (1+, 2+) was limited. From 1989 to 1990, the proportion of trout increased from 30 to only 40% of the total catch, but from 1991 to 1994, it was significantly higher (60–80%) than that of charr. Total trout biomass increased to a maximum in 1992 and then decreased so that the biomass of 1994 was nearly similar to that of 1989, that is before the start of the charr removal. Back‐calculated lengths of trout from otoliths showed that 2+ and 3+ trout caught in the pelagic were growing consistently faster over previous years than those caught in the littoral, while this was not the case for the 4+ fish. Therefore, the hypothesis was partially supported; the growth rate of trout increased (age groups 1+ to 4+), while the density of juvenile trout (1+, 2+), but not the older trout (3+, 4+), increased after the removal of charr.  相似文献   

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

Jonathan J. Low  Fran Igoe  John Davenport  Simon S. C. Harrison 《Ecology of Freshwater Fish》2011,20(4):537-547

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.  相似文献   

Antipredator behaviour of naïve Arctic charr young in the presence of predator odours and conspecific alarm cues     

T. Lautala  H. Hirvonen 《Ecology of Freshwater Fish》2008,17(1):78-85

Abstract –  We investigated how Arctic charr young respond behaviourally to olfactory cues from skin-damaged conspecifics, charr-fed pikeperch, and the combination of food-deprived pikeperch and skin-damaged conspecific cues in a two-channel Y-maze fluviarium test arena. Significant antipredator responses were found to skin-damaged conspecifics in three behavioural traits, to charr-fed pikeperch in two traits and to the combination of pikeperch and skin-damaged conspecific cues in all six behaviours investigated. The combination of predator and conspecific cues significantly increased spatial avoidance and cautiousness to approach the source of scent compared with odours from charr-fed predators. The results suggest that damage-released alarm cues exist in charr, and they strengthen the antipredator responses in conspecifics. As the charr used different behaviours and levels of response in the presence of different cues, they seem to have sophisticated skills to distinguish between different odour combinations and be able to adjust their behaviour according to the current predation risk level.  相似文献   

Adfluvial and fluvial life history variations and migratory patterns of a relict charr, Salvelinus confluentus, stock in west-central Idaho, USA     

C. B. Watry  D. L. Scarnecchia 《Ecology of Freshwater Fish》2008,17(2):231-243

Abstract –  Life history strategies and migratory patterns of 71 adult radio-tagged bull trout, Salvelinus confluentus , were studied in the Secesh River watershed within the South Fork Salmon River (SFSR) sub-basin in west-central Idaho, USA during 2003 and 2004. In both years, upstream migrations occurred during late June and early July, migrations into two spawning tributaries during late July and early August, spawning from mid-August through mid-September, and rapid downstream (postspawning) migrations from late August to mid-September. Primary over-wintering areas were Loon Lake, the lower Secesh River (downstream of Loon Creek), and the lower SFSR (downstream of the confluence with the Secesh River). Loon Lake evidently provides sufficient production to allow the adfluvial life history strategy to persist and predominate in the Secesh River, while the fluvial life history strategy was previously found to predominate in the nearby East Fork SFSR. Adfluvial, nonconsecutive-year migrations were the predominant life history strategy. Only seven fish made consecutive-year migrations to Lake Creek; however, only one of these fish, a female, utilised a spawning tributary in both years and showed spawning tributary fidelity. Three consecutive-year migrants and three in-season migrants showed over-wintering site fidelity by returning to Loon Lake in September, 2004. The life history variations observed for bull trout in the Secesh River watershed are similar to those observed for bull trout throughout their range and to those of other charr species worldwide, yet the development of distinct migration patterns demonstrate the adaptability of the species to a range of available habitats.  相似文献   

Effects of photoperiod on sex steroids and gonad maturation in Arctic charr     

Marianne Frantzen  Arne M. Arnesen  Brge Damsgrd  Helge Tveiten  Helge K. Johnsen 《Aquaculture (Amsterdam, Netherlands)》2004,240(1-4):561-574

Four groups of Arctic charr (age 3+), previously exposed to natural photoperiod, were subjected to different photoperiod regimes from February 20: Simulated natural photoperiod (SNP; Tromsø 70°N), continuous light (LD 24:0) followed by short day (LD 6:18) from either May 1 (L_Feb–May) or June 25 (L_Feb–June), or continuous light (LD 24:0) throughout the experiment (L_Continuous). In females, peak levels of estradiol-17β and testosterone were 6 and 10, 6 and 7, and 3 and 5 weeks advanced, in L_Feb–May, L_Feb–June and L_Continuous, respectively, whereas in males plasma levels of 11-ketotestosterone peaked 8 weeks earlier in L_Feb–May and L_Feb–June than in SNP and L_Continuous. Median ovulation time in L_Feb–May and L_Feb–June was advanced by 10 weeks compared to SNP and L_Continuous, and median spermiation time (first observation of running milt in each individual) in L_Feb–May, L_Feb–June and L_Continuous was advanced by 10, 7 and 5 weeks, compared to SNP. A switch from long to short day early in the reproductive cycle (L_Feb–May and L_Feb–June) apparently resulted in stronger synchronization of both ovulation and spermiation. Ovulation in L_Feb–May and L_Feb–June occurred over 3 weeks (L_Feb–May) and 8 weeks (L_Feb–June), as compared to 10 weeks in the SNP group, whereas all males (except one individual) began spermiating over a period of 3 weeks (L_Feb–June), or less (L_Feb–May), as compared to 7 weeks in the SNP group. Lack of a short day stimulus (L_Continuous), on the other hand, resulted in larger variation in the timing of final maturation, with ovulation and spermiation being spread over 15 weeks. Low egg survival in L_Feb–May (17% versus 60% and 97% for L_Continuous and SNP) indicate that a long day signal of 10 weeks early in the reproductive cycle may be too short to ensure good egg and sperm quality. Photoperiod manipulation did not affect the proportion of maturing fish.  相似文献   

Migration of anadromous white-spotted charr <Emphasis Type="Italic">Salvelinus leucomaenis</Emphasis>, as determined by otolith strontium: calcium ratios     

Takaomi?AraiEmail author  Aya?Kotake  Takefumi?Kitamura 《Fisheries Science》2005,71(4):731-737

ABSTRACT:   The migratory history of anadromous white-spotted charr Salvelinus leucomaenis collected from Japanese coastal waters, was examined in terms of strontium (Sr) and calcium (Ca) uptake in the otolith, by means of wavelength dispersive X-ray spectrometry using an electron microprobe. Otolith Sr concentration or Sr : Ca ratios of anadromous S. leucomaenis , fluctuated strongly along the life history transect in accordance with the migration (habitat) pattern from sea to fresh water. The anadrmous S. leucomaenis showed phase L (low Sr : Ca ratio) from the core to the point 1000–2500 µm distant, averaging 1.3 × 10⁻³ to 2.7 × 10⁻³ and thereafter, the ratios increased sharply, being higher than 5.0 × 10⁻³ to 10.0 × 10⁻³. These findings indicated that otolith Sr : Ca ratios reflected individual life histories, enabling a sea habitat to be identified from a freshwater habitat in this species.  相似文献   

Arctic charr in Britain and Ireland – 15 species or one?     

C. E. Adams  P. S. Maitland 《Ecology of Freshwater Fish》2007,16(1):20-28

Abstract –  From both a modern and a historical perspective there is little doubt that the Arctic charr, Salvelinus alpinus , in Britain and Ireland (as well as elsewhere) is a 'difficult' species. Historically 15 separate species have been recognised from populations in Britain and Ireland and there have been recent attempts to reassert these specific names. Here we review the evidence for the status of these 'species'. We conclude that the evidence for these 15 being afforded full species status is poor. However, both historical and contemporary data show that Salvelinus alpinus (Linnaeus 1758) in Britain and Ireland exhibits levels of variability in form that is much greater than in other species. We argue that a comprehensive genotypic and phenotypic survey of charr populations in Britain and Ireland is required to determine the full extent of variability and the status of populations with a view of providing suitable protection.  相似文献   

Effects of stocking of piscivorous brown trout, Salmo trutta L., on stunted Arctic charr, Salvelinus alpinus (L.)   总被引：1，自引：0，他引：1  

B. Damsgård  A. Langeland 《Ecology of Freshwater Fish》1994,3(2):59-66

To study the effects on a stunted freshwater population of Arctic charr, Salvelinus alpinus (L.), two groups of large (26–45 cm) individually tagged brown trout, Salmo trutta L., were released and recaptured with gillnets after 1, 7, 11 and 63 weeks. One group of trout was trained on a fish diet before release, and the other, reared on commercial dry pellets, served as a control. Specific growth rates in both groups were negative 1 week after release and approached zero after 63 weeks. Condition factor and internal fat content decreased during the experiment. Although only 11% of the trout stomachs examined contained fish prey, charr represented 79% of the total stomach weight content. Gillnet samples of charr before and 63 weeks after the release of trout indicated a decreasing population size of charr. Individual growth and mean length of charr increased after release of trout, especially for charr at age 4 years. After the release of trout, 35% of the charr were longer than 20 cm as compared with 6% before the release.  相似文献   

Effects of dietary n−3 polyunsaturated fatty acids on lipid and fatty acid composition and haematology of juvenile Arctic charr Salvelinus alpinus (L.)     

X. Yang  J. L. Tabachek  T. A. Dick 《Fish physiology and biochemistry》1994,12(5):409-420

The effect of dietary n−3 and n−6 polyunsaturated fatty acids (PUFAs) on juvenile Arctic charr Salvelinus alpinus (L.) were investigated with respect to essential fatty acid (EFA) deficiency and lipid metabolism using one commercial and 12 casein-based test diets. Arctic charr with mean weight of 1.6g were fed test diets for 12 weeks at 10°C. At the end of the feeding, blood, liver, muscle and whole fish were sampled to determine haematocrit, haemoglobin, water content, lipid and fatty acid composition. Charr fed diets containing 0–1.0% n−3 PUFAs showed typical EFA deficiency signs: fatty liver or elevated water content in whole body or substantial accumulation of 20:3n−9 in liver polar lipids. These signs were less apparent or disappeared when charr were fed diets containing ≥ 2.0% 18:3n−3. No correlation was found between dietary PUFAs and haematocrit or haemoglobin values. Significant changes in fatty acid composition of liver polar lipids in charr fed dietary PUFAs indicate that charr can convert 18:3n−3, 18:2n−6 and 20:5n−3 into long-chain PUFAs. While charr had a direct incorporation of dietary 22:6n−3 into liver and muscle there appears to be preferential utilization of n−3 PUFAs for elongation and desaturation. The conversion of 18:4n−3 was less in muscle than in livers. These findings, combined with data on growth and feed efficiency reported previously by Yang and Dick (1993), indicate that charr require 1−2% dietary 18:3n−3 (dry weight). Small amounts of dietary 18:2n−6 (up to 0.7%) did not have detrimental effects on charr.  相似文献