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The enhancement of the salmon stocks in the Simojoki and Tornionjoki Rivers by stocking parr in the rapids
Abstract
Stocking Salmo salar parr in the rapids is a suitable method for improving smolt production in the rivers studied. -from Authors
... The aim of this study was to compare the phenotypic diversity in two wild Atlantic salmon stocks of the northern Baltic Sea (Tornionjoki and Simojoki salmon stocks) and their respective reared strains. Both of the stocks were supported by stocking with young salmon of their own genetic origin from the 1980s to the 2000s (Jutila and Pruuki, 1988;Jutila et al., 2003b;Romakkaniemi et al., 2003;Jokikokko and Jutila, 2009). Adaptive phenotypic variation between the wild stocks and differences between the wild and reared stocks were investigated by estimating marine survival, the sea migration pattern and the sea age at maturity. ...
... The main reason for the decline in natural production was overfishing in the sea and the consequent lack of spawners in the rivers (Jutila and Pruuki, 1988). Because the regulation of salmon fishing was not effective enough to prevent the decline in the natural salmon stocks, it became necessary to produce reared parr and smolts for release (Jutila and Pruuki, 1988;Romakkaniemi, 2008). ...
... The main reason for the decline in natural production was overfishing in the sea and the consequent lack of spawners in the rivers (Jutila and Pruuki, 1988). Because the regulation of salmon fishing was not effective enough to prevent the decline in the natural salmon stocks, it became necessary to produce reared parr and smolts for release (Jutila and Pruuki, 1988;Romakkaniemi, 2008). Together with supportive stocking, habitat restoration and fishing regulation improved the status of stocks, and large-scale supportive stocking was ended in both rivers during the first years of the 2000s. ...
... In Finland, the rearing of parental fish stocks in artificial conditions throughout their life has been common in producing hatchery-reared juveniles of Baltic Sea salmon stocks. Successive hatchery generations are unavoidable in a situation where original spawning areas in nature have been destroyed (Säisä et al., 2003), and artificial rearing has been a necessary way to protect the endangered stocks in face of the lack of reproduction areas and the excessive pressure of the mixed stock sea fishery (Jokikokko and Jutila, 2005;Jutila and Pruuki, 1988;Romakkaniemi et al., 2003). Some Baltic salmon stocks, like Iijoki and Oulujoki ones have been entirely maintained by broodstocks for many generations Koljonen, 1989). ...
... In this study, eggs for juvenile rearing were produced by both hatchery-reared broodstocks (the same reared Simojoki parents were used for 5-7 years) and sea-ranched parents captured as returning spawners at the Simojoki River mouth (used only in the year of capture). The Simojoki River has a wild stock, but it has been supported by releases of reared parr and smolts since the mid-1980s (Jutila and Pruuki, 1988). Our aim was to compare the effects of these two types of hatchery rearing (hatchery-reared or sea-ranched parents) on the life-history traits of the resulting smolts. ...
... The river supports a naturally reproducing and genetically differentiated Atlantic salmon stock (Koljonen, 2001). The natural stock of Simojoki salmon has been supported by annual releases of hatchery-reared parr and smolts from the mid-1980s to the early 2000s due to the endangered state of the natural stock in that period (Jutila and Pruuki, 1988;Jutila et al., 2003b). ...
Life-history traits such as growth, survival, sea migration and age at sexual maturity in the sea were compared between Carlin-tagged hatchery-reared Atlantic salmon smolts (Salmo salar) originating from hatchery broodstocks (reared) or naturally ascending spawners captured (sea ranched). The ranched parents included both wild (born in nature) and reared individuals (released as parr or smolts). All smolts were reared in similar hatchery conditions, and they were tagged and released as two-year-olds in the Simojoki River in 1986–2007. The recapture rates did not differ between the progeny groups, although the tagged smolts of the reared parents were larger than those of ranched parents at time of release. The captive salmon with ranched parents were at average heavier during their second winter at sea, but not later. Salmon with ranched parents more frequently migrated to feed in the Main Basin of the Baltic Sea, further from the home river of the salmon stock. The proportions of multi-sea-winter returners were 30% and 69% in salmon with reared and ranched parents, respectively. The different patterns of migration and sea age at maturity of these parental progeny groups suggest that differences in the life history of brood fish may cause distinct, possibly even genetic differences in the progenies.
... Salmon normally ascend the river up to 110 km from the sea, and the parr density estimates are based on results from this area (Jokikokko and Jutila, 1998). Before major human impacts in the 1950s, the salmon production is estimated to have been about 75 000 smolts per year (Jutila and Pruuki, 1988). ...
... Salmon do not reproduce naturally in the Oulujoki, Iijoki, and Kemijoki rivers, which are regulated for hydroelectric power generation. Only the Tornionjoki has a naturally reproducing salmon stock, although even this is supported by stocking (Jutila and Pruuki 1988). The original Oulujoki stock is extinct, and the present hatchery-reared salmon constitute a genetically unique hybrid stock containing genes from the original Oulujoki stock, the Tornionjoki stock, the Iijoki stock, and the Skellefteälv stock and possibly from other stocks, too (Koljonen 1989). ...
Atlantic salmon (Salmo salar L.) stocks in the Baltic Sea are mainly exploited during their sea migration. The offshore fishery in the feeding grounds of these salmon permitted us to analyse the migrations of certain stocks on the basis of tag recovery data. Four salmon stocks from rivers draining into Bothnian Bay (25°E, 65.5°N) were selected for study. During 1984-1991, about 135 000 2-year-old hatchery-reared smolts were tagged and released. We applied logit models, with the site of recovery as a multicategory response variable, to analyse the distribution of tag recoveries in the Baltic Sea feeding grounds. The results showed the combined influence of stock, prey abundance, and smolt size on the spatial marine distribution of the salmon. Although stock-specific sea migration patterns were apparent, annual environmental factors had a stronger influence on the sea migration route of salmon than did the stock factor. The salmon released as small smolts (total length [Formula: see text] 17.0 cm) were more frequently caught farther from the release site than were those released as larger smolts (>17 cm). The abundance of suitable prey (age 0+ herring) in the year of smolt release was found to be a key factor influencing the migration distance. The salmon released in the years of strong herring recruitment in the Gulf of Bothnia had a higher probability to stay in the Bothnian Sea for feeding and not to migrate farther south.
... Salmon stocks originating from the currently closed rivers have been maintained by rearing offspring from both hatchery broodstocks and sea-ranched parents [16]. Since the 1980s, fishing pressure has been heavy, and it has threatened the naturally reproducing stocks [12,15,35,36]. In addition, since the 1990s, high post-smolt mortality for unknown reasons has impaired the state of the natural stocks [26,[37][38][39]. ...
Origin and age was determined for individual fish caught in offshore catches of Atlantic salmon stocks (Salmo salar L.) in the Baltic Sea over the years 2000–2009. DNA microsatellite loci and smolt age were used to probabilistically assign returning spawners to their stock of origin. Data for this study were based on approximately 2600 catch samples of the five most common wild and four sea-ranched, hatchery-reared stocks. Spawning age, and sex ratio differed both within and between these wild, and sea-ranched groups. The females were mainly (78.7%) two sea-winters old and the males usually (68.7%) only one sea-winter old. In both sexes, the mean age at maturity was lower in the hatchery-reared, sea-ranched stocks than in naturally reproducing stocks. In the 2000s, there was a weak decreasing trend in the male spawning age, but not in that of females. The sex-ratio of the spawners was female dominant in the naturally reproducing stocks, but male dominant in hatchery-reared stocks. Published historical data from two of the same rivers suggest that the majority of males were multi-sea-winter spawners in the 1930s, and variation in the age distribution of the spawners has become narrower and skewed towards a younger age in the present data (2000–2009) compared to the earlier situation.
... Two-year-old smolts and 1-year-old and 1-summer-old parr have been extensively released into the two remaining undisturbed salmon rivers on the Finnish coast of the Baltic Sea, the rivers Simojoki and Tornionjoki, since the mid-1980s to support the endangered wild salmon stocks (Jutila & Pruuki 1988). Hatchery reared parr were used to increase parr and smolt production in rapids with few or no natural parr, allowing the reared parr time in the river to adapt to living in the wild (Jokikokko & Jutila 1998). ...
... Year a native, naturally reproducing salmon stock (Koljonen, 2001), but due to the weak status of the stock, supporting releases were carried out from the 1980s until 2003 (Jutila and Pruuki, 1988;Jokikokko and Jutila, 1998;Kallio-Nyberg et al., 2011b). The estimated wild smolt production was 36 000 in 2010 (WGBAST, 2011). ...
Cost–benefit analysis was applied to estimate the net present value (NPV) of Atlantic salmon (Salmo salar, Carl Linnaeus) hatchery smolt releases and the spatial distribution of the present value of benefit [PV(B)] in the Baltic Sea. The benefit was assessed for the commercial fishery and separately from hatchery-reared and wild smolts. Data on Carlin tagging and on the proportions of individual salmon stocks in the commercial catches were used. The NPV of hatchery smolt releases appeared to be negative with current rearing costs and the range of applied discount rates (2–4%), and especially with the currently low overall survival of salmon smolts in the sea (<2%). A 5% recapture rate had been needed for a positive outcome. The PV(B) of wild salmon smolts was higher than that of reared salmon smolts due to their larger catch size and higher recapture rate. Both wild and reared salmon mostly benefited the fishermen operating in the Baltic Main Basin, while few fish and minor revenues were left for the coastal and river fisheries in the Bothnian Bay. Six salmon stocks, three wild and three reared, originating from the Bothnian Bay accounted for 60% of the total Atlantic salmon catch in the Baltic Sea. The current economical benefits from hatchery smolt releases to professional fishermen barely overcome the costs they cause to rearing and releasing counterparties.
Atlantic salmon is often a focal species of restoration efforts throughout the north Atlantic and it is therefore an excellent case study for how best to design programmes to address and mitigate threats and correct population declines. This perspective is written to promote the work that has been accomplished towards restoration of Atlantic salmon populations and synthesize how we believe the lessons can be used effectively to support efforts by management agencies to restore populations. We reviewed where restoration is needed for Atlantic salmon, agreed on definitions for three levels of successful restoration, and then applied these criteria to 49 published papers focused on Atlantic salmon restoration. We identified 16 successful examples of restoration among 49 papers reviewed and discussed what interventions led to success versus failure. We then addressed key questions about when hatchery stocking should be used as part of a restoration measure and whether local restoration efforts are enough when these wide-ranging species encounter broad-scale changes in the north Atlantic, specifically related to issues of climate change and to marine survival. We advise to avoid restoration as much as possible by protecting and managing existing populations and when restoration is necessary, problems should be identified and addressed in partnership with river users. With appropriate resources and research to resolve ongoing mysteries, restoration of lost Atlantic salmon populations is absolutely feasible.
Koska voimalaitosrakentaminen estää vaelluskalojen nousun jokiin, aiheuttaa se kalataloudellisen menetyksen, jonka
kompensointiin toiminnanharjoittaja on velvoitteella määrätty. Tässä raportissa tarkastellaan rakennettujen jokien
kalatalousvelvoitteita suhteessa viimeaikaiseen tutkimustietoon ja sen pohjalta tehtyihin arvioihin kalakannoille ja
kalataloudelle aiheutuneista vahingoista. Tarkastelun pääkohteina olivat Oulujoki ja Kemijoki, joiden lisäksi yleisempi
arviointi tehtiin Ii-, Kymi- ja Pielisjoelle. Selvitys tehtiin Maa- ja metsätalousministeriön tutkimuslaitokselle antamana
tulostavoitteena.
Selvityksen mukaan olosuhteet ovat olennaisesti muuttuneet velvoitteiden määräämisen ajoista, mikä on perusteltavissa uudella, aiempaa huomattavasti laajemmalla ja muuttuneella tiedolla vaelluskalakantojen tuotannosta, istutuspoikasten säilyvyydestä, istutusten kannattavuudesta sekä kalakantojen monimuotoisuudesta. Olosuhteita ovat
muuttaneet lisäksi rakennettujen jokivesistöjen laajamittaiset kunnostus- ja vesiensuojelutoimenpiteet.
Uudet arviot Kemi- ja Iijoen lohen ja meritaimenen menetetystä poikastuotannosta perustuvat jokien tuotantoalojen
tarkasteluihin sekä uuteen tutkimustietoon Tornionjoen vaelluspoikastuotannosta ja sen tavoitetasosta. Luonnontilaisen Oulujoen hehtaarikohtainen vaelluspoikastuotanto arvioitiin muita Perämereen laskevia lohijokia suuremmaksi ja
Kymijoella puolestaan kaikkia em. jokia selvästi suuremmaksi. Vaellussiian osalta arviot tehtiin merkintätutkimusten ja
historiallisten saalistietojen perusteella.
Uudet arviot Kemi-, Ii- ja Oulujoen lohen ja meritaimenen kompensaatiotasoista ovat moninkertaisia nykyvelvoitteisiin
nähden. Myös Ii- ja Oulujoen vaellussiian osalta uudet arviot ovat nykyisiä kompensaatioita huomattavasti korkeampia. Arviot uusista kompensaatiotasoista esitetään aiempien kalatalousvelvoitteiden tapaan kalojen istutuspoikasina.
Olennaista velvoitteiden määrittämisessä on kuitenkin niiden arvo, joten velvoitteiden toimeenpanotapa tulee arvioida tapauskohtaisesti.
Atlantic salmon (Salmo salar L.) stocks in the Baltic Sea are mainly exploited during their sea migration. The offshore fishery in the feeding grounds of these salmon permitted us to analyse the migrations of certain stocks on the basis of tag recovery data. Four salmon stocks from rivers draining into Bothnian Bay (25°E, 65.5°N) were selected for study. During 1984-1991, about 135 000 2-year-old hatchery-reared smolts were tagged and released. We applied logit models, with the site of recovery as a multicategory response variable, to analyse the distribution of tag recoveries in the Baltic Sea feeding grounds. The results showed the combined influence of stock, prey abundance, and smolt size on the spatial marine distribution of the salmon. Although stock-specific sea migration patterns were apparent, annual environmental factors had a stronger influence on the sea migration route of salmon than did the stock factor. The salmon released as small smolts (total length ≤ 17.0 cm) were more frequently caught farther from the release site than were those released as larger smolts (>17 cm). The abundance of suitable prey (age 0+ herring) in the year of smolt release was found to be a key factor influencing the migration distance. The salmon released in the years of strong herring recruitment in the Gulf of Bothnia had a higher probability to stay in the Bothnian Sea for feeding and not to migrate farther south.
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