A phylogeographic survey of brook charr (Salvelinus fontinalis) in Algonquin Park, Ontario based upon mitochondrial DNA variation

Forty-nine populations of brook charr (Salvelinus fontinalis) from Algonquin Park lakes and rivers were analysed for mitochondrial DNA variation. Haplotypic distributions of wild fish in the Algonquin Park region of Ontario, Canada, predominantly reflect postglacial dispersal patterns into the region in spite of substantial hatchery plantings. Two major refugial groupings colonized this region. Northern and eastern watersheds (Amable du Fond, Bonnechere, and northern Petawawa), were colonized primarily by haplotype 1 fish (B1 phylogenetic assemblage), while Oxtongue River, southern Petawawa, and York River populations were colonized predominately by fish from the B2 and A mtDNA phylogenetic assemblages. Fish with haplotypes in the A and B2 phylogenetic assemblages are common in the Lake Huron drainage. All watersheds in the Park drain into the Ottawa River, except the Oxtongue drainage (part of the Lake Huron watershed). This suggests that early glacial outflows south of the Algonquin Park region (Kirkfield-Trent) may have been colonized by fish that initially invaded ‘Ontario island’ (south-western Ontario), while fish which invaded northern Algonquin Park were derived from a different refugial grouping(s) which may have involved colonization both up the Ottawa River drainage, and/or from a more westerly (Mississippian) refugial grouping. A majority of the populations in Algonquin Park have been planted with hatchery reared brook charr since the 1940s. The Hills Lake or ‘Domestic’ strain was used almost exclusively for these plantings. Comparisons of mtDNA haplotypic distributions in hatchery and wild fish suggests that hatchery females had minimal spawning success and/or their progeny had poor survivorship in the wild.     

An examination of the post-planting success of hatchery brook charr possessing different mitochondrial DNA haplotypes

Previous mtDNA and allozyme studies of brook charr Salvelinus fontinalis from northern Ontario lakes that had been extensively stocked with a government hatchery strain, yielded results that were incongruous with a neutral theory of selection in the mtDNA genome. A single haplotype (haplotype 1) predominated in all the fish sampled from these lakes, which is consistent with the observed distribution of this haplotype in northern portions of the species range. However, haplotype 1 does not occur in a high frequency within the hatchery strain. In a direct survivorship experiment, of 1500 fish stocked into an Ontario lake in the spring of 1994 containing a native population of brook charr, no significant differences between stocking and recapture mtDNA distributions were observed in the summer of 1994. However, a survey of young of the year in the following spring did not reveal the presence of any 'private' hatchery haplotypes. Significant differences in the distribution of mtDNA haplotypes were observed in two stocked lakes compared to those in the putative source hatchery strain. Haplotype 1 predominated in both these stocked lakes, suggesting that fish with this haplotype possessed increased survivorship.     

Mitochondrial DNA variation of Salvelinus species found in Finland

Mitochondrial DNA (mtDNA) was purified from the Arctic charr, Salvelinus alpinus , the brook charr, Salvelinus fontinalis , and the lake charr, Salvelinus namaycush , and digested with restriction enzymes Ava II, Hinf I, Eco R V, Pst I and Xba I. Two Arctic charr samples were from natural populations and they represented two different morphotypes of Arctic charr. All other studied populations were hatchery maintained. Eight additional restriction enzymes and double digestions were employed to study morphotypes of Arctic charr. We distinguished two morphotypes with restriction enzyme Nci I. Sequence divergence among mtDNA types was 2.9–3.8% between S. alpinus and S. fontinalis , 3.4–4.6% between S. alpinus and S. namaycush , and 4.7–5.3% between S. fontinalis and S. namaycush . lntraspecific variation was lowest in Arctic charr, the average of nucleon diversity for three populations being 0.179, while for brook charr and for lake charr nucleon diversity was 0.334 and 0.550, respectively. According to the number of mtDNA types, it is obvious that introduction to Finland and hatchery propagation have not greatly affected the mtDNA variation of brook charr or lake charr.     

An invasive crayfish affects egg survival and the potential recovery of an endangered population of Arctic charr

1. Many fish stocks have declined, because of overharvesting, habitat destruction and introduced species. Despite efforts to rehabilitate some of these stocks, not all are responding or are recovering only slowly. 2. In freshwater systems, introduced crayfish are often problematic, and it has been suggested that their egg predation could reduce recruitment in depleted stocks of native fish. 3. Here, we report the results of a field experiment, using experimental cages, on the extent of predation on eggs of great Arctic charr (Salvelinus umbla) in Lake Vättern, Europe’s fifth largest lake. Here, the great Arctic charr has declined dramatically and is listed as critically endangered. 4. We were able to partition the total loss rate of eggs into background mortality, predation by introduced signal crayfish (Pacifastacus leniusculus) and predation by native fish. The mortality rate of charr eggs because of crayfish was estimated at more than five times that because of native fish. Of the total loss of eggs, 80% is believed to be caused by crayfish and 14% by fish, with 6% being natural background mortality. 5. In a worst case scenario, our data infer that only 25% of the original number of eggs would survive, compared with 75% in the absence of crayfish. This could impair recovery of the stock of the endangered great Arctic charr in Lake Vättern. 6. Contrary to earlier claims that crayfish predation on eggs of great Arctic charr is insignificant, our results indicate that crayfish predation may exceed fish predation and suggest that the abundance of signal crayfish on the spawning sites of great Arctic charr should be managed.     

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

To determine the genetic relationship of anadromous and resident life-history types within and among drainages, and compare several hatchery strains to their progenitor populations, brook charr Salvelinus fontinalis were examined for allozyme and mitochondrial DNA variation. Greater genetic similarity of sympatric anadromous and resident charr was found compared to similar life-history forms allopatrically, suggesting the two life-history types are not reproductively isolated. Low divergence among the mtDNA haplotypes suggests that the two life-history types are members of the same evolutionary lineage. Population differentiation from mtDNA data exceeded that from estimates based on allozymes. Genetic deviations from expectations suggest that the hatchery strains were derived from few individuals.     

Feeding rate of slimy sculpin and burbot on young lake charr in laboratory reefs

Synopsis Predation and contaminants are two possible factors in the poor recruitment of young lake charr Salvelinus namaycush in the Great Lakes. We measured the feeding rate of slimy sculpins Cottus cognatus and burbot Lota lota on young lake charr (uncontaminated young from eggs of a hatchery brood stock and contaminated young from eggs of Lake Michigan lake charr) in laboratory test chambers with a cobble substrate. The median daily consumption rate of sculpins for all tests was 2 lake charr eggs (N = 22 tests; 95% confidence interval, 0–13) and 2 lake charr free embryos (N = 31 tests; 95% confidence interval, 0–10). Feeding rate did not differ between hatchery and contaminated prey. Slimy sculpins continued to feed on lake charr when another prey organism, the deepwater amphipod Pontoporeia hoyi, was present. Feeding by burbot on free embryos (4–36 d^–1) increased as the mobility of young increased, but burbot consumed about 10% of their body weight weekly in free-swimming young (140–380 d^–1). Predation on lake charr eggs by sculpins could be considerable over the 100 to 140 d incubation period, and burbot could eat large numbers of free-swimming lake charr as the young fish left the reef. Predation pressure on young lake charr may inhibit rehabilitation of self-sustaining populations of lake charr on some reefs unless a critical egg density has been reached.     

Genetic risk of domestication in artificial fish stocking and its possible reduction

Genetic hazards associated with the stocking of fish juveniles produced in hatcheries were studied with simple mathematical models. Domestication is the process of acquiring a genetic characteristics that are advantageous in a hatchery environment but that are disadvantageous in a natural environment due to the selection pressure in the hatchery differing from that in the natural environment. Conditions for the propagation of mutants enhancing domestication were obtained for a variety of stocking strategies specified by parameters related to hatchery productivity and kind of brood stock used. By using this, the possibility of reducing the risk of domestication was studied. As a means of reducing the risk, selective use of wild-born individuals for brood stock was considered. The effectiveness of this was analyzed for both the cases where all brood stock is collected from the wild, and the male brood stock is collected from the wild and the female brood stock is born and reared in a hatchery. We also estimate how much hatchery release can be increased without increasing the risk by employing these means. It is concluded that the use of only male brood stock from the wild is not very effective in reducing the risk of domestication. Further, it is concluded that selective use of the wild-born individuals of both sexes for brood stock is highly desirable if the contribution of released individuals to the natural reproduction is high. In other words, substantial increase of hatchery release may be possible while keeping risk at a level comparable to that under moderate hatchery release, if it is accompanied by the selective use of wild-born individuals for brood stock.     

Assessment of the stocked or wild origin of anadromous brown trout (Salmo trutta L.) in a Danish river system, using mitochondrial DNA RFLP analysis

Declines in the number of anadromous brown trout in the Karup River in Denmark, due to environmental degradation, led to the stocking of large numbers of hatchery trout during the 1980s. This practice was gradually replaced by stocking with the offspring of electrofished local trout The genetic contribution of the hatchery fish to the current population of anadromous trout in the river was estimated by restriction fragment length polymorphism analysis of mitochondrial DNA, using seven restriction endonucleases. Fish from the hatchery strain as well as from five locations in the river system, and from a further unstocked river were screened. Eight haplotypes were observed. The distribution and frequencies of the observed haplotypes revealed little genetic differentiation among stocked populations. The hatchery strain differed significantly from the stocked populations. One haplotype which was found at a high frequency in the hatchery strain was almost absent from the stocked populations. This suggests that the genetic contribution of the hatchery trout to the current population is much less than would be expected from the number of stocked fish. The possible reasons for the failure of the hatchery trout to contribute to the gene pool, and also the implications for conservation biology, are discussed.     

Population dynamics and potential of fisheries stock enhancement: practical theory for assessment and policy analysis

The population dynamics of fisheries stock enhancement, and its potential for generating benefits over and above those obtainable from optimal exploitation of wild stocks alone are poorly understood and highly controversial. I review pertinent knowledge of fish population biology, and extend the dynamic pool theory of fishing to stock enhancement by unpacking recruitment, incorporating regulation in the recruited stock, and accounting for biological differences between wild and hatchery fish. I then analyse the dynamics of stock enhancement and its potential role in fisheries management, using the candidate stock of North Sea sole as an example and considering economic as well as biological criteria. Enhancement through release of recruits or advanced juveniles is predicted to increase total yield and stock abundance, but reduce abundance of the naturally recruited stock component through compensatory responses or overfishing. Economic feasibility of enhancement is subject to strong constraints, including trade-offs between the costs of fishing and hatchery releases. Costs of hatchery fish strongly influence optimal policy, which may range from no enhancement at high cost to high levels of stocking and fishing effort at low cost. Release of genetically maladapted fish reduces the effectiveness of enhancement, and is most detrimental overall if fitness of hatchery fish is only moderately compromised. As a temporary measure for the rebuilding of depleted stocks, enhancement cannot substitute for effort limitation, and is advantageous as an auxiliary measure only if the population has been reduced to a very low proportion of its unexploited biomass. Quantitative analysis of population dynamics is central to the responsible use of stock enhancement in fisheries management, and the necessary tools are available.     

Diet, growth and competitive abilities of sympatric whitefish forms in a dense introduced population: results of a stocking experiment

The food of five whitefish stocks Coregonus lavaretus planted in Lake Vuokalanjärvi consisted mainly of zooplankton and insects taken from the water surface. The amount of benthic food in the diet of the two sparsely gill-rakered (23 and 28 rakers) stocks increased from the age of 2 years onwards. The growth of whitefish was slow in all stocks. The densely gill-rakered stock (50–51 rakers) originating from the same lake system as Lake Vuokalanjärvi grew faster than the other stocks, and the food consumption of 4- and 5-year-old fish belonging to this stock was nearly double compared with the other stocks. The habitat choice of the whitefish differed between the stocks even in the densely-rakered stocks classified as the same form. A stock with flexible habitat use and feeding habits is most likely to succeed. Introducing whitefish stocks from distant areas is not advisable.     

Why do salmonid antipredator responses weaken in hatchery rearing?

The Arctic charr of Lake Saimaa are the most endangered fish population in Finland, and reintroduction programs have been unsuccessful. Low success of reintroduction programs has drawn attention to behavioural properties of hatcheryreared fish. Mortality due to predation often is a principal cause of failure. Antipredator behaviour may degenerate rapidly under hatchery conditions due to (i) reduced genetic variation in antipredator behaviour and/or (ii) selection that would favour bold and fast growing individuals and disfavour predator awareness supposedly associated with slow growth. To test the relative importance of these two factors we first analysed the amount of variation in innate antipredator responses between and within families of hatchery‐bred Arctic charr of the Lake Saimaa stock. We then tested whether fast growing individuals would show reduced responses to chemical cues from their natural predators compared to their slow growing counterparts. Based on the results we propose procedures for maintaining and improving antipredator skills of hatchery‐reared salmonids.     

Plasma cortisol and sex steroid levels in Great Lakes coho salmon (Oncorhynchus kisutch Walbaum) in relation to fecundity and egg survival

Plasma 11-ketotestosterone and cortisol levels in spawning male and female coho salmon (Oncorhynchus kisutch Walbaum) collected from a Lake Erie (Pennsylvania) stock were significantly lower (P less than 0.01) than in stocks of coho salmon at a comparable stage of sexual development collected from Lakes Ontario (two stocks) or Michigan. Plasma testosterone levels in female coho salmon from Lake Erie were significantly lower (P less than 0.01) than in females from Lake Ontario or Lake Michigan stocks. There were no significant differences in plasma testosterone levels in the males, or 17 beta-estradiol levels in male or female salmon of the four stocks sampled from the three study lakes. This apparent dysfunction in androgen and cortisol secretion in the Lake Erie stock is correlated with and may account for the low fecundity and poor expression of secondary sexual characteristics in that stock.     

Regional structure despite limited mtDNA sequence diversity found in the endangered Huchen, <Emphasis Type="Italic">Hucho hucho</Emphasis> (Linnaeus, 1758)

We evaluate the hypothesis of no geographic structure in the Huchen (Hucho hucho), a large, predatory salmonid endemic to the Danube basin. Forty-seven individuals sampled from throughout the Huchen’s native range were genetically characterized. Extremely limited sequence diversity across 1,800 bases of mtDNA (the complete control region and partial NADH-1 subunit) evidenced by four closely related mtDNA haplotypes was found. Nonetheless, the geographic distribution of mtDNA repeats (5–10, 82-bp long copies per individual) as well as allelic diversity across two microsatellite loci indicated large-scale geographic structure between the north-western (Austria and Slovenia) distribution area and eastern (Slovakia and Ukraine) or southern (Bosnia-Herzegovina and Montenegro) sample sites. An extremely slow rate of substitution for the H. hucho mtDNA is considered along with the alternative hypotheses to explain the limited mtDNA diversity. Considering the regional genetic structure implied by our data, we advocate restrictions on the transport of brood fish or yearlings across the range of the species distribution and sale of Huchen across international boundaries. Future genetic analysis to support local conservation and monitoring efforts must focus on developing a high-resolution screen that may be applied to identify hatchery versus naturally reproduced individuals in the wild.     

Evidence of a genetic component in the seasonal return pattern of Atlantic salmon, Salmo salar L.

We tested the null hypothesis that differences in the seasonal return patterns between stocks of Atlantic salmon, Salmo salar L., are a result of a direct response to the environment, and not under genetic control. Two stocks were used in the experiments, originating from the R. Figga and R. Imsa, respectively. In their native habitat fish from the former are known to return to the home stream as adult salmon early in the summer, while from the latter return during late summer and autumn. By rearing these stocks in the same hatchery and releasing smolts of both stocks together at three sites in southern Norway, it was demonstrated that salmon from the R. Figga stock returned earlier to coastal Norway than salmon from the R. Imsa stock, as maturing adults. Thus, we reject the hypothesis that these stocks are genetically identical in this trait. Within both stocks, multi-sea-winter fish returned earlier than one-sea-winter fish. Within stocks, there was no significant difference in time of return between salmon released as 1- and 2-year-old smolts, or between fish reared from parents ascending the R. Imsa early or late in the season.     

On the Origin of the Lacustrine Charr <Emphasis Type="Italic">Salvelinus alpinus</Emphasis> Complex from the Kolyma and Sea of Okhotsk Basins

Morphological and genetic characteristics are used for the analysis of the origin of charrs from the lakes of the Kolyma basin (Chuk, Gek, Gulyaevskoe-4, Gulyaevskoe-6, and Lenkovoe) and the Sea of Okhotsk basin (Lake Chistoe). In addition to these samples, the fragments of the control region of mitochondrial DNA (CR mtDNA, 550-bp) and exon 2 of recombination activating gene 1 (RAG1, 899-bp) are sequenced in the charrs from lakes Dzhul’etta and Cherechen’ (Kolyma basin) and lakes Elikchanskie, Bol’shoi Mak-Mak, Ueginskoe (Sea of Okhotsk basin), Ulakhan-Silyan-Kyuel’ (Yana River basin) as well as in northern Dolly Varden from the Kamchatka River. The charr from Lake Chistoe is represented by northern Dolly Varden. In the charrs from lakes Chuk, Gek, Gulyaevskoe-4, Gulyaevskoe-6, Lenkovoe, Cherechen’, Elikchanskie, Bol’shoi Mak-Mak, and Ueginskoe, the haplotypes of mtDNA of the Bering group (a haplogroup of northern Dolly Varden) are revealed. Based on the morphological and RAG1 data, populations of charrs from these lakes belong to the Salvelinus alpinus complex. A transfer of mtDNA of northern Dolly Varden to the charrs from the Kolyma and Sea of Okhotsk basins occurred during the last postglacial expansion and subsequent hybridization. Based on the results of morphological and genetic analysis, the charrs from the Kolyma and Sea of Okhotsk basins cannot be unambiguously referred to the phylogenetic groups of Eurasian Arctic charr or Taranets charr. The presence of mtDNA haplotypes of the Arctic group (a haplogroup of Taranets charr) in the populations of lakes Dzhul’etta, Maksi, and Ueginskoe shows a possibility of their belonging to the group of Taranets charr.     

Body pigmentation pattern to assess introgression by hatchery stocks in native Salmo trutta from Mediterranean streams

Five qualitative and seven quantitative colouration and spotting pattern features were measured in 23 brown trout Salmo trutta populations and two hatchery stocks. Simultaneously, the LDH‐C1 *, a diagnostic locus fixed for *90 and *100 alleles in stocking and native populations from southern Europe, respectively, was analysed to classify the brown trout studied according to their origin: native, hatchery stock and hybrids. The three genotypes showed significant differences in the colouration and spotting features and a discriminant function analysis could correctly identify 79% of the individuals. The most discriminating variables were dorsal fin margin colour, number of opercular spots, presence of the preopercular mark and diameter of black spots. Given the low cost, ease and possibility of field identification of native fish, the results indicate great opportunities for the application of morphological‐based classification models on the conservation and management of native brown trout stocks.     

A program for successful muskellunge management—A Minnesota success story

Minnesota has established a successful muskellunge, Esox masquinongy, stocking program as a result of a series of research studies that enabled area fisheries managers to make informed management decisions. The previous propagation and stocking program (pre-1982) reared muskellunge progeny from Shoepack Lake near the Minnesota–Ontario border, but these fish were not attaining trophy size. Protein electrophoresis showed there were two different muskellunge strains in the state. A controlled study was conducted on progeny from natural muskellunge populations from Leech and Shoepack lakes. Fish from these populations, together, were used to stock two other Minnesota lakes, and their growth rates, age of maturity, and maximum size attained were compared. Leech Lake muskellunge grew faster and attained a larger maximum size than the Shoepack Lake strain. As a result, a new stocking program based on the Leech Lake strain was developed. Because it was difficult to collect Leech Lake gametes, the Minnesota Department of Natural Resources created seven brood stock lakes using Leech Lake progeny. As a result of combining genetic considerations, new research on spawning sites, more restrictive harvest regulations, and catch-and-release fishing, anglers’ catch of trophy-sized muskellunge in Minnesota has increased.     

Meristic variation among world hatchery stocks of rainbow trout,Salmo gairdneri Richardson

Synopsis Sixteen meristic characters were examined among 10 stocks of rainbow trout to establish their inter- and intrastock variability and relative discriminating power. The number of vertebrae, dorsal fin rays, scales above and below and lateral line, oblique scale rows and pectoral fin rays were found to be the most useful meristic characters in identifying stocks. Examination of the extent of meristic divergence among 10 hatchery or naturalized stocks from various regions of the world, using analysis of variance, the generalized distance function and per cent overlap, revealed that each stock exhibited highly significant differences in at least one meristic character, thereby demonstrating a high degree of intraspecific variability in meristic expression.In multivariate terms, stocks from Idaho and Alaska were almost totally divergent from all other stocks examined. Multivariate analysis of meristic features proves to be a useful method for identifying the extent of phenotypic variability among and within divergent stocks of rainbow trout. The observed meristic variability in test stocks of hatchery fish is seemingly genetically set within the limits previously described for native populations of rainbow trout.     

Mitochondrial DNA variation in cattle of South China: origin and introgression

Ten restriction endonucleases were used to investigate the mitochondrial DNA restriction fragment length polymorphism (mtDNA RFLP) of 11 native cattle breeds and one cultivated cattle breed in South China. Twenty-three restriction morphs were detected, which can be sorted into five haplotypes. A phylogenetic tree of the haplotypes was constructed by using the 'upgMa' method. Our study showed that haplotype I and II are identical to the zebu (Bos indicus) and taurine (Bos taurus) haplotypes, respectively. Zebu and taurine were the two major origins of cattle populations in South China, and the zebu probably had more influence on the native cattle population than taurine did. Haplotype III is identical to haplotype I of yak (Bos grunniens), which was only detected in the Diqing cattle breed. Haplotype IV was detected for the first time. This haplotype, found only in Dehong cattle, might be from an independent domestication event, probably from another Bos indicus population. Divergence of haplotypes I and IV occurred about 268,000-535,000 years ago, much earlier than the 10,000-year history of cattle husbandry. Our results also suggest a secondary introgession of mtDNA from yak to Diqing cattle.     

Phylogeography and postglacial dispersal of arctic charr Salvelinus alpinus in North America

Restriction fragment length polymorphism analysis of mitochondrial DNA (mtDNA) was used to reconstruct postglacial dispersal routes of arctic charr Salvelinus alpinus in North America. Twelve of 35 restriction enzymes detected polymorphisms among representative populations, revealing two distinct lineages with an estimated nucleotide divergence of 1.32%. Subsequent screening of 869 fish from 54 populations with four diagnostic restriction enzymes showed that these lineages have largely allopatric distributions, suggesting their dispersal from separate northern and eastern glacial refugia. In addition, geographical and genetic structure among eastern populations suggested the existence of a second eastern refuge. Among the three lineages, the most divergent (Arctic) lineage occurred from Alaska east to northern Labrador. Quebec, New Brunswick, and New England were colonized by a second (Laurentian) lineage, and Labrador by a third group. Contact between refugial groups was only detected in two Labrador populations. The Arctic lineage was highly differentiated from eastern North American and European haplotypes, and probably diverged during the early Pleistocene. By contrast, the Laurentian and Labrador groups were similar to Old World charr, suggesting a shared ancestry during the mid-Pleistocene. In addition, the close relationship between Labrador and Laurentian charr indicates their probable divergence during the Wisconsinan glaciation.