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The paper presents the results of the sterlet sturgeon Acipenser ruthenus reintroduction into the Kama Reservoir (Perm Krai, Russia) by sterlet fry from hatcheries into the reservoir since 2001. The effectiveness of hatchery releases was evaluated by monitoring gillnet sampling 2014–2020. The results showed that the species was reported throughout entire Kama Reservoir, which contrasts with 1988–1994 data, when the species was registered only at the upper part of the reservoir near the Kama River mouth. The highest number and biomass values of catch per unit effort (CPUE) of the sterlet were found in submerged river channels – the deepest habitats with flow conditions which are close to the ecological requirements of the species. The distribution of the sterlet within the channel biotopes of the reservoir is defined by reduced variability. The biggest individuals and the widest size range of the sterlet were typical for the upper area of the reservoir and Chusovskoy Bay, which have the greatest flow. The smallest sizes were typical for fish from catches near the dam of the reservoir, which is consistent with the published data on the distribution of sterlet in reservoir conditions. The presented results may indicate the artificial formation of the sterlet stock in the Kama Reservoir maintained by hatchery releases. The revealed distribution of the sterlet in the reservoir determines the direction of further research on natural reproduction and thus formation of an artificially formed population. Also, future studies are required to assess the possibility of hybridization of the sterlet of artificial origin with natural populations of the species, since the low genetic diversity of the sterlet released into the Kama Reservoir which can lead to irreversible loss of genetic individuality of the natural stocks of the species in the catchment of upper course of the Kama River.

The paper presents the results of the sterlet sturgeon Acipenser ruthenus reintroduction into the Kama Reservoir (Perm Krai, Russia) by sterlet fry from hatcheries into the reservoir since 2001. The effectiveness of hatchery releases was evaluated by monitoring gillnet sampling 2014-2020. The results showed that the species was reported throughout entire Kama Reservoir, which contrasts with 1988-1994 data, when the species was registered only at the upper part of the reservoir near the Kama River mouth. The highest number and biomass values of catch per unit effort (CPUE) of the sterlet were found in submerged river channels - the deepest habitats with flow conditions which are close to the ecological requirements of the species. The distribution of the sterlet within the channel biotopes of the reservoir is defined by reduced variability. The biggest individuals and the widest size range of the sterlet were typical for the upper area of the reservoir and Chusovskoy Bay, which have the greatest flow. The smallest sizes were typical for fish from catches near the dam of the reservoir, which is consistent with the published data on the distribution of sterlet in reservoir conditions. The presented results may indicate the artificial formation of the sterlet stock in the Kama Reservoir maintained by hatchery releases. The revealed distribution of the sterlet in the reservoir determines the direction of further research on natural reproduction and thus formation of an artificially formed population. Also, future studies are required to assess the possibility of hybridization of the sterlet of artificial origin with natural populations of the species, since the low genetic diversity of the sterlet released into the Kama Reservoir which can lead to irreversible loss of genetic individuality of the natural stocks of the species in the catchment of upper course of the Kama River. [ABSTRACT FROM AUTHOR]

We estimated the proportion of hatchery and natural fall spawning chum salmon returning to the Amur River using chemical markers specific to hatchery-origin fry. We used otolith microchemistry technique to identify fish with artificial origin among returning spawners. First, we found that juveniles of artificial origin had higher values of the Sr:Ca molar ratio of the otoliths’ edge zone compared with juveniles of natural origin, what can be related to the use of rearing feed produced from raw materials of marine origin rich in strontium. Then we observed that most of the spawners from Anyuisky Hatchery and from the Amur River mouth at the start of the spawning migration has also the higher value of Sr:Ca molar ratio of the juvenile zone of otoliths. Also, adults with higher values of the Sr:Ca molar ratio are characterized by a skewed right in the peak of the age distribution. Both, the age structure and phenological shift in the time of spawning migration of individuals with higher value of the used chemical marker corresponds to results of studies on hatchery-produced chum salmon completed at different parts on Northern Pacific. The results of this study will be used in the management of Amur fall chum salmon fisheries, and also demonstrates the necessity of the development of specific measures for increasing the survival of juvenile anadromous salmonids released at large rivers and exposed to prolonged freshwater migration to the ocean. As a further application of the methodology, we plan to identify the markers specific to each of the hatcheries and main spawning tributaries belonging to Amur River catchments. This will be an important step in the evaluation of the contribution of different stocks in mixed fisheries and also in the estimation of the effect of hatchery releases on naturally spawning stocks of Amur fall chum.Following to, our results may indicate the applicability of this approach for the determination of artificial-origin fish in a mixed sample of the Amur fall chum salmon.

We estimated the proportion of hatchery and natural fall spawning chum salmon returning to the Amur River using chemical markers specific to hatchery-origin fry. We used otolith microchemistry technique to identify fish with artificial origin among returning spawners. First, we found that juveniles of artificial origin had higher values of the Sr:Ca molar ratio of the otoliths' edge zone compared with juveniles of natural origin, what can be related to the use of rearing feed produced from raw materials of marine origin rich in strontium. Then we observed that most of the spawners from Anyuisky Hatchery and from the Amur River mouth at the start of the spawning migration has also the higher value of Sr:Ca molar ratio of the juvenile zone of otoliths. Also, adults with higher values of the Sr:Ca molar ratio are characterized by a skewed right in the peak of the age distribution. Both, the age structure and phenological shift in the time of spawning migration of individuals with higher value of the used chemical marker corresponds to results of studies on hatchery-produced chum salmon completed at different parts on Northern Pacific. The results of this study will be used in the management of Amur fall chum salmon fisheries, and also demonstrates the necessity of the development of specific measures for increasing the survival of juvenile anadromous salmonids released at large rivers and exposed to prolonged freshwater migration to the ocean. As a further application of the methodology, we plan to identify the markers specific to each of the hatcheries and main spawning tributaries belonging to Amur River catchments. This will be an important step in the evaluation of the contribution of different stocks in mixed fisheries and also in the estimation of the effect of hatchery releases on naturally spawning stocks of Amur fall chum. Following to, our results may indicate the applicability of this approach for the determination of artificialorigin fish in a mixed sample of the Amur fall chum salmon. [ABSTRACT FROM AUTHOR]

This article examines the social and political implications of the geographically widespread and cross-cultural oral narratives related to the releases of salmon into the rivers of the Pacific Northwest through the destruction of weir-dams. Key themes in these narratives provide insights into indigenous concepts of reciprocity and authority, which in turn reveal dimensions of social organization and intercommunity interactions from a new perspective. These narratives explicitly foreground the inevitable tensions between communities that relied on salmon and also sought to prioritize their own interests, seeking exclusive use of weirs, occasionally to the detriment of other groups. This study illustrates how these narratives convey episodes of contradictory interests, exploitation, social struggle, reconciliation, and a moral charter for communities over a broad area. The analysis also highlights how the messages of these narratives are just as pertinent today as they were in the past. [ABSTRACT FROM AUTHOR]

Release of age‐0 hatchery‐reared fall Chinook salmon, Oncorhynchus tshawytscha (Walbaum), in the Snake River resulted in up to 30‐fold increases in salmon consumption by non‐native smallmouth bass, Micropterus dolomieu Lacepѐde. In an upper river reach, smallmouth bass fed intensively during a release in May, but Chinook salmon consumption returned to pre‐release levels within 1–2 days as hatchery‐reared fish quickly emigrated downstream. The predation response during a June release located farther downstream was dissimilar. Chinook salmon consumption increased to a lesser extent (11‐fold), lasted several days (~4) and no changes in feeding intensity were evident. Estimated numbers of age‐0 hatchery‐reared Chinook salmon lost to short‐term predation varied by year and study reach and ranged from 12,007 (6.03% of those released) to 210,580 (14.6% of those released) fish. Short‐term, intense feeding by smallmouth bass can contribute significantly to mortality of hatchery‐reared fish and should be considered when supplementing populations with hatchery juveniles. [ABSTRACT FROM AUTHOR]

Along the coast of Shandong Province in China, an extensive hatchery-release programme has been conducted for more than 10 years. However, no information has been reported concerning the long-term effects on the wild population resulting from the release of large numbers of juveniles in Portunus trituberculatus. In this study, sequence variation of swimming crab P. trituberculatus based on the mitochondrial control region was investigated for 946 swimming crabs at the releasing sites from 2012 to 2014. The result showed that the wild P. trituberculatus was characterized by high genetic diversity indices, and not significantly different from the previous study. Low FST values were estimated among the groups of different years and different sites, which suggested no genetic differentiation found in the wild population after the stock enhancement programme. Hence, the long-term extensive hatchery release programme has not affected the genetic structure of wild P. trituberculatus populations along the coast of Shandong Province. [ABSTRACT FROM AUTHOR]

The effects of genetics and rearing environments on morphometric variation among hatchery stocks of Asian sea bass (300 days post-hatch) were investigated by multivariate analyses of 21 truss measurements. Ninety-day-old fingerlings from four stocks, including Ang Sila, Bang Pakong, Meklong and Paknam, were stocked in the same earthen pond and reared for 270 days. These stocks were genetically different from each other. Principal component analysis (PCA) of body measurements suggested very little body shape difference among populations. Subsequently, discriminant function analysis (DFA) was used to assign individuals to their stock of origin. The accuracy of assignment was highest for the Ang Sila stock (77.7%) followed by Bang Pakong (72.4%), Meklong (66.1%) and Pak Nam (65.5%). Analysis of the Ang Sila stock reared in two locations, Chantaburi and Prachuab Kirikhan provinces, suggested that salinity is an important factor affecting body shape differentiation. DFA identified the two most discriminating truss measures, both of which were correlated with head size. The classification functions assigned individuals to groups with 100% accuracy. The results demonstrated that multivariate morphometries is an effective tool for detecting variation among stocks in Asian sea bass aquaculture. [ABSTRACT FROM AUTHOR]

Abstract: Recent genetic studies, meta‐analyses, and retrospective analyses have documented reduced productivity of wild salmon and steelhead Oncorhynchus mykiss that interbreed with hatchery‐reared fish, raising concerns about the long‐term viability and recovery of at‐risk stocks. In 2007, the Oregon Department of Fish and Wildlife discontinued a Coho Salmon Oncorhynchus kisutch hatchery program at the Salmon River to support recovery of a wild Coho Salmon population in the Oregon Coast Evolutionarily Significant Unit. This decision constituted a unique management “experiment,” allowing for direct measurement of the wild population's response after the discontinuation of a decades‐old hatchery program. We used a before–after, control–impact design to examine whether selected viability metrics of the naturally produced population in the Salmon River changed after the hatchery program ended. We compared metrics for the 2006–2013 broods, representing periods after the hatchery program ended, to those for the 1995–2005 broods, when the hatchery program was still releasing 200,000 smolts annually. We also examined neighboring populations during similar time periods to account for changes or variation due to other factors. Although hatchery‐origin spawners previously had accounted for most of the adults returning to the Salmon River, the naturally produced population did not collapse, and two viability metrics improved significantly after the Coho Salmon hatchery program ended: (1) adult abundance increased and (2) spawn timing expanded and moved closer to the historical timing. Recruits‐to‐spawner ratios in the Salmon River, although initially low, are now approximately equal to those of neighboring populations. The results indicate that hatchery closure can be an effective strategy to promote wild population recovery. However, considerable variability in population trends and environmental conditions will require continued monitoring to verify the long‐term resilience and viability of the wild population. [ABSTRACT FROM AUTHOR]

A simple approach is described that uses the ratio of catches among a reference and a target stock to estimate their relative depletion. The catch-ratio estimator was simulation tested to identify conditions under which it can be expected to provide precise and unbiased estimates of relative depletion. The catch-ratio estimator is strongly affected by diverging catch reporting rate and catchability among reference and target stocks. Outside of these issues, the approach is unbiased for a range of life-history characteristics, temporal patterns in exploitation rate and changes in the age vulnerability to fishing. Coupled with the depletion estimates of a data-rich stock, the catch ratio estimator can be used to infer depletion of a data-limited stock without an assessment. [ABSTRACT FROM AUTHOR]

Copyright of Archives of Veterinary Medicine / Arhiv Veterinarske Medicine is the property of Scientific Veterinary Institute Novi Sad and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Development of broodstock of the green mud crab (Scylla paramamosain) was assessed under three different captive growout protocols viz. in the open fibre glass tanks (T1), in plastic boxes (T2) floating on fibre glass tanks and in plastic drawer/compartment (T3) for a period of 5 months under the Centre for Marine and Coastal Studies (CEMACS), Universitiy Sains Malaysia (USM). The male (M) and female (F) mud crab were cultured separately to maintain virginity. Suitability of both the sexes were evaluated considering the weight gain (size), survival and intactness of limbs during harvesting. Result of the present study revealed that, irrespectives of growout protocols, growth of mud crab happened following the sigmoid pattern. A noticeable intersexual weight attainment was observed with significantlyhigher (p<0.05) weight gain for the males. Meanwhile, growth was influenced by the culture protocols for both the sexes with significant (p<0.05) weight gain in outdoor tanks (M= 319.75 g, F= 246.17 g) followed by outdoor floating boxes (M= 250.50 g, F= 198.70 g) and indoor compartment (M= 246.40 g, F= 178.50 g). Survival and the proportion of intact crabs under indoor compartment and outdoor floating boxeswere significantly higher (p<0.05) than out door tank culture system. The result of the present study suggested that, outdoor growout protocol could be followed for faster broodstock development purposes to reduce the dependence on natural broodstock for hatchery operations. [ABSTRACT FROM AUTHOR]

Trout fishing is one of the primary recreational activities in the southern Appalachians, with large amounts of fish stocked on a regular basis. However, very little is known regarding the fate of hatchery reared carcasses not captured by anglers, representing a likely important ecological resource to local communities. We tested the efficacy of underwater video to characterize short term decomposition and consumption by aquatic scavengers of native brook and non-native rainbow trout, Salvelinus fontinalis and Oncorhychus mykiss. This study took place on the Cherokee Qualla Boundary in North Carolina, a location with one of the highest riverine stocked trout densities in the eastern United States. During May 2017, 10 waterproof cameras were deployed for 1-hour intervals on each carcass twice daily for a period of 5 days. We observed that 75.3% of recorded video contained river chub, Nocomis micropogon, with only 24.7% visited by crayfish, with a maximum of 9 and a mean of 1.93 for N. micropogon. Half of the carcasses were removed within 2 days. Based on natural history evidence and some trail cameras, we believe that otters were removing carcasses. Otters showed no preference for either trout species. Underwater video allowed us to characterize initial decomposition within stream diurnal scavengers in a short period using a visual, non-destructive low-cost method. Future studies should monitor large mammalian scavengers to further elucidate the role of fish stocking on aquatic communities.

Copyright of Revista Brasileira de Engenharia Agricola e Ambiental - Agriambi is the property of Revista Brasileira de Engenharia Agricola e Ambiental and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The effectiveness of fishing regulations that result in the release of some angler-caught fish depends on accurate knowledge of the postrelease mortality of those individuals. In the Laurentian Great Lakes, Lake TroutSalvelinus namaycushare a major component of recreational fisheries; across large regions of the lakes, they are managed with length limit and daily quota regulations assuming a 15% postrelease mortality rate. Due to concerns regarding the accuracy of that rate, we conducted a tagging study to estimate Lake Trout postrelease mortality in Lakes Superior and Huron, and we examined environmental and fishing factors that influenced the return rates of tagged fish. The basic study design was to compare tag return rates between two groups: (1) a treatment group comprising fish that were caught and released by anglers; and (2) a control group comprising fish that were caught via trap net and released. Tag return rates for the angler-caught group were evaluated in relation to depth of capture, surface temperature at release (ST), fishing method, anatomical hook site, play time, handling time, and barotrauma. Tag return rates for angler-caught fish declined significantly with increasing ST; the other factors’ effects on tag return rates were generally small. For Lake Superior, model-averaged (Akaike’s information criterion) postrelease mortality estimates incorporating ST were 15.0% (SE = 5.6%) at STs less than 10°C, 42.6% (SE = 3.0%) at STs of 10–16°C, and 43.3% (SE = 3.6%) at STs greater than 16°C. Model-averaged estimates for Lake Huron were 52.5% (SE = 26.8%) at STs less than 10°C, 45.2% (SE = 14.0%) at STs of 10–16°C, and 76.4% (SE = 5.4%) at STs greater than 16°C. Based on these findings, alternative fishery management regulations that limit recreational catch-and-release angling of Lake Trout in the Great Lakes may be prudent. Current management policies based on an assumed 15% postrelease mortality are likely underestimating the total numbers of Lake Trout that are removed by recreational anglers. Received January 26, 2017; accepted April 29, 2017 Published online June 26, 2017 [ABSTRACT FROM PUBLISHER]

Hatchery programs that are designed to aid recovery of natural populations of anadromous salmonids, including steelheadOncorhynchus mykiss, require locally derived, natural-origin broodstock. In such programs, achieving smoltification size thresholds may require extending hatchery rearing beyond age 1. We compared out-migration survival and travel rates of 142,990 PIT-tagged steelhead smolts released at age 1 (S1 rearing strategy) or age 2 (S2 rearing strategy) over five release years at Winthrop National Fish Hatchery (WNFH, Okanogan County, Washington). An S2 rearing cycle produced larger smolts with more uniform size distributions, resulting in higher survival during the first portion of their out-migration than for S1 smolts in three of the five release years. The S2 smolts migrated more rapidly to the ocean than S1 smolts in all years except 2011 and arrived in the Columbia River estuary 5.4 d earlier on average than the S1 smolts. The S1 steelhead that did not leave during the volitional release were subsequently forced from the hatchery to measure their survival. Nonvolitional S1 migrants were smaller and had survival rates that were 2.3–66.3 times lower than those of S1 steelhead that left WNFH on their own. The same was true for S2 steelhead, but the magnitude of the survival difference between volitional migrants and fish forced from the raceways was less variable and ranged from 2.5- to 4.6-fold. We conclude that S2 rearing can be a successful strategy for producing smolts from local natural-origin broodstock, with out-migration survival and travel times that are equivalent to or better than those of S1 smolts produced from nonlocal broodstock. Received July 25, 2016; accepted March 31, 2017 Published online May 31, 2017 [ABSTRACT FROM PUBLISHER]

Survival rates among European eels, Anguilla anguilla (Linnaeus, 1758), on-grown using a formulated diet in a commercial aquaculture facility, were compared with glass eels from the same cohort following their transition to a natural prey diet in the laboratory. Treatments included zero, 42-day, and 196-day periods of grow-out prior to 30-day experimental periods when eels were fed Chironomus spp. larvae (10 tanks, each containing 240-L water and 40 glass or 10 on-growing eels; 12:12 hr photoperiod; water temperature 18°C). All glass eels survived, compared to 87% (42-day) and 99% (196-day) for on-grown eels. Although the eels on-grown for 196 days had a high survival rate, they did lose weight. Farm-reared eels may have accumulated sufficient resources over the 196-days to survive the first 30 days after weaning from a formulated diet, but not for an additional 30 days (84% survival). Lack of superior survival rates among on-grown eels challenges the presumed benefits of releasing on-grown eels for population restoration. [ABSTRACT FROM AUTHOR]

Many ecosystems continue to experience rapid transformations due to processes like land use change and resource extraction. A systems approach to maintaining natural resources focuses on how interactions and feedbacks among components of complex social-ecological systems generate social and ecological outcomes. In recreational fisheries, residential shoreline development and fish stocking are two widespread human behaviors that influence fisheries, yet emergent social-ecological outcomes from these potentially interacting behaviors remain under explored. We applied a social-ecological systems framework using a simulation model and empirical data to determine whether lakeshore development is likely to promote stocking through its adverse effects on coarse woody habitat and thereby also on survival of juvenile and adult fish. We demonstrate that high lakeshore development is likely to generate dependency of the ecosystem on the social system, in the form of stocking. Further, lakeshore development can interact with social-ecological processes to create deficits for state-level governments, which threatens the ability to fund further ecosystem subsidies. Our results highlight the value of a social-ecological framework for maintaining ecosystem services like recreational fisheries. [ABSTRACT FROM AUTHOR]

Stocking density causes changes in behaviour and physiology of aquatic animals and high density can cause oxidative damage in living cells. Therefore, experiments were designed to investigate the effects of stocking density on the oxidant-antioxidant response (glutathione (GSH), glutathione peroxidase (GSH-Px), catalase (CAT), and malondialdehyde (MDA)), digestive enzyme activity trypsin), and heat shock protein 70 (HSP70) of narrow clawed crayfish (Astacus leptodactylus). The experiment was conducted to assess effects by stocking 3, 6, 9 and 12 crayfish/m2. Crayfish were stocked into 12 fiberglass tanks, three replicates per treatment and fed for 45 days. Our results indicated that activity of GSH-Px, MDA, and GSH levels increased in hepatopancreas (p<0.05) and muscle tissues (p<0.05) with increasing stock concentration while CAT activity decreased p<0.05). Trypsin and HSP70 insignificantly increased in haemolymph. In conclusion, oxidative stress biomarkers were negatively influenced by increased quantitative changes in stocking density. [ABSTRACT FROM AUTHOR]

Hatchery 'recycling' programs have been used to increase angling opportunities by re-releasing fish into a river after they returned to a hatchery or fish trap. Recycling is intended to increase opportunities for fishermen, but this strategy could affect wild fish populations if some recycled fish remain in the river and interact with wild fish populations. To quantify hatchery return and angler harvest rates of recycled steelhead, we conducted a 2-year study on the Cowlitz River, Washington. A total of 1051 steelhead were recycled, including 218 fish that were radio-tagged. Fates of recycled steelhead were similar between years: 48.4% returned to the hatchery, 19.2% were reported captured by anglers, and 32.4% remained in the river. A multistate model quantified the effects of covariates on hatchery return and angler harvest rates, which were positively affected by river discharge and negatively affected by time since release. However, hatchery return rates increased and angler harvest rates decreased during periods of increasing discharge. A total of 21.1% (46 fish) of the radio-tagged steelhead failed to return to the hatchery or be reported by anglers, but nearly half of those fish (20 fish) appeared to be harvested and not reported. The remaining tagged fish (11.9% of the radio-tagged population) were monitored into the spawning period, but only five fish (2.3% of the radio-tagged population) entered tributaries where wild steelhead spawning occurs. Future research focused on straying behaviour, and spawning success of recycled steelhead may further advance the understanding of the effects of recycling as a management strategy. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Many salmonid fish populations are threatened by genetic homogenization, primarily due to introgressive hybridization with hatchery-reared conspecifics. By applying genomewide analysis using two molecular marker types (1986 SNPs and 17 microsatellites), we assessed the genetic impacts of inadvertent gene flow via straying from hatchery releases on wild populations of Atlantic salmon in the Gulf of Finland, Baltic Sea, over 16 years (1996-2012). Both microsatellites and SNPs revealed congruent population genetic structuring, indicating that introgression changed the genetic make-up of wild populations by increasing genetic diversity and reducing genetic divergence. However, the degree of genetic introgression varied among studied populations, being higher in the eastern part and lower in the western part of Estonia, which most likely reflects the history of past stocking activities. Using kernel smoothing and permutation testing, we detected considerable heterogeneity in introgression patterns across the genome, with a large number of regions exhibiting nonrandom introgression widely dispersed across the genome. We also observed substantial variation in nonrandom introgression patterns within populations, as the majority of genomic regions showing elevated or reduced introgression were not consistently detected among temporal samples. This suggests that recombination, selection and stochastic processes may contribute to complex nonrandom introgression patterns. Our results suggest that (i) some genomic regions in Atlantic salmon are more vulnerable to introgressive hybridization, while others show greater resistance to unidirectional gene flow; and (ii) the hybridization of previously separated populations leads to complex and dynamic nonrandom introgression patterns that most likely have functional consequences for indigenous populations. [ABSTRACT FROM AUTHOR]

Naturally reproduced Chinook SalmonOncorhynchus tshawytschacontribute substantially to the fishery in Lake Ontario. The Salmon River, a Lake Ontario tributary in New York, produces the largest numbers of naturally spawned Chinook Salmon, with parr abundance in the river often exceeding 10 million. In the spring of each year, large numbers of hatchery salmonid yearlings—potential predators of Chinook Salmon parr—are released into the Salmon River by the New York State Department of Environmental Conservation. We sought to examine predation on Chinook Salmon parr in the Salmon River during May and June prior to out-migration. Over the 4 years examined (2009–2012), annual consumption of Chinook Salmon parr by hatchery-released yearling steelheadO. mykissand Coho SalmonO. kisutchranged from 1.5 to 3.3 million and from 0.4 to 2.1 million, respectively. In 2009, FallfishSemotilus corporaliswere estimated to consume 2.9 million Chinook Salmon parr. Predation was higher in May, when the average TL of Chinook Salmon parr was 44.5 mm, than in June. Fallfish were also important predators of naturally reproduced steelhead subyearlings, consuming an estimated 800,000 steelhead in 2009. Hatchery-released yearling salmonids consumed 13.8–15.3% of the Chinook Salmon parr that were estimated to be present in the Salmon River during 2010–2012. Earlier releases of hatchery salmonid yearlings could reduce the riverine consumption of Chinook Salmon parr by facilitating the out-migration of yearlings prior to Chinook Salmon emergence. Received February 23, 2015; September 29, 2015 [ABSTRACT FROM PUBLISHER]

This paper reports on successful hatchery production of the winged pearl oyster, Pteria penguin , without the use of live micro-algae. Larval nutrition was provided by commercially available micro-algae concentrates, Instant Algae® (“Isochrysis 1800®” and “Pavlova 1800®”, Reed Mariculture Inc., San Jose, CA, USA). Larvae were first transferred to settlement tanks on day 17 when their mean antero-posterior measurement (APM) was 240.2 ± 8.6 μm. Approximately 6.4% of larvae survived to day 17 and more than 700,000 eyed pediveligers were transferred to settlement tanks between day 17 and day 25. Approximately 33,000 spat were harvested from spat collectors on day 105, representing a survival rate of 4.7% from the eyed pediveliger stage. Growth and development of larvae in this study were superior to those reported in a prior study that used a ternary live micro-algae diet to feed P. penguin larvae. Our results indicate that the products used in this study proved nutritious for P. penguin larvae and supported normal growth and development through settlement. The use of commercially available micro-algae concentrates as a replacement for live micro-algae in pearl oyster hatcheries supports development of simplified larval rearing protocols, without live micro-algae culture, that are more appropriate to Pacific island nations. Statement of relevance This paper reports for the first time on successful hatchery production of pearl oysters without the use of live micro-algae. Successful replacement of live micro-algae with commercially available micro-algae concentrates as a larval food source supports development of simpler, cheaper hatchery facilities, and larval rearing protocols that are more appropriate to Pacific island nations. [ABSTRACT FROM AUTHOR]

Subyearling (age‐0) hatchery summer‐run Chinook Salmon Oncorhynchus tshawytscha have been released into the Columbia River in mid‐June from Wells Fish Hatchery, Washington, since 1993, but release‐to‐adult survival (SAR) under this strategy has been low. I used paired releases of four broods of coded‐wire‐tagged age‐0 Chinook Salmon released in mid‐May (early release [ER] group) and mid‐June (late release [LR] group) to evaluate whether advancing the release date could improve SAR. Additionally, passive integrated transponder tags implanted in a subsample of each release group were used to estimate emigration rate and release‐to‐McNary Dam survival of juvenile fish. Mean migration rate from release to McNary Dam was significantly faster for LR fish than for ER fish. No among‐year difference in mean survival from release to McNary Dam was observed between ER and LR groups, although differences were observed within years. Mean overall SAR was significantly greater for ER fish than for LR fish. These results suggest that altering the release date of age‐0 Chinook Salmon at Wells Hatchery would enhance return survival. [ABSTRACT FROM AUTHOR]

Throughout the world, several efforts currently exist for restocking clawed lobster ( Homarus sp.) by releasing mass amounts of postlarvae in the wild. Therefore, optimization of hatchery techniques and evaluation of their influence on lobster postlarvae behavior at release time are of interest. This study looked at the effects of light regime (photoperiod and light intensity) on growth, survival, and behavior of American lobster postlarvae (stage IV) at release time. Results showed that photophase length did not induce any significant differences in growth and survival at 100 lx. Light intensity did not affect larval development at 16 h photophase. Results showed a significant interaction between the two factors (photoperiod and light intensity) on larval survival, but not on growth. When compared to other studies, our results indicate that the feeding time (night vs. day) may be of importance for optimizing growth and survival of early larvae. Behavior results clearly demonstrated that the age of the lobster at postlarvae stage IV had more influence than the day length or light intensity, and that the light intensity induced more variability than the day length. The results suggest that a light regime of 16 h photophase at 1000 lx light intensity, both survival and settling behavior at release time. [ABSTRACT FROM AUTHOR]

An outbreak of the sessile peritrich Zoothamnium duplicatum in a pilot, commercial-scale Limulus polyphemus hatchery resulted in the loss of ∼96% (40,000) second/third instar larvae over a 61 day period. peritrich growth was heavy, leading to mechanical obstruction of the gills and physical damage. The peritrichs were controlled without resultant loss of juvenile crabs by administering 10 ppm chlorine in freshwater for 1 h and the addition of aquarium grade sand; a medium into which the crabs could burrow and facilitate cleaning of the carapace. Peritrich identity was confirmed from a partial SSU rDNA contiguous sequence of 1343 bp (99.7% similarity to Z. duplicatum ). [ABSTRACT FROM AUTHOR]

To better understand the influence of hatchery practices on wild populations of Lake TroutSalvelinus namaycush, we used a landscape genetic approach to tease apart the population genetic patterns expected due to natural processes versus hatchery stocking, i.e., human-mediated gene flow. In several lakes across our study area in Vermont, the presence of exogenous mitochondrial DNA haplotypes supported our human-mediated gene flow hypothesis. Microsatellite DNA analyses showed introgression of hatchery genotypes into the wild populations. Nonetheless, clustering patterns within river drainages and signatures of isolation by distance were consistent with natural postglacial colonization. We conclude that though the genetic makeup of Vermont Lake Trout populations has been influenced by stocking, a lack of genetic bottlenecks and concordance with landscape processes suggests that much of the indigenous genetic diversity remains intact. We were able to attribute departures from expectations based on natural genetic patterns to hatchery introgression in specific lakes. To preserve the adaptive potential of local populations that have persisted since the last ice age, we suggest areas for which hatchery supplementation could be minimized. Received June 16, 2014; accepted September 12, 2014 [ABSTRACT FROM AUTHOR]

Captive propagation of Pacific salmon is routine, but few captive breeding programs have been conducted to successfully re-establish extirpated wild populations. A captive breeding program for endangered Sakinaw Lake sockeye salmon was established from 84 adults between 2002 and 2005, just prior to extirpation of the wild population. After several years of absence, sockeye salmon released from captivity returned to spawn in Sakinaw Lake in 2010 and in all years thereafter. Freshwater survival rates of released hatchery fry and naturally produced progeny of reintroduced sockeye salmon have not limited abundance of the reintroduced population. In contrast, marine survival rates for Sakinaw sockeye salmon have been <1%, a level that precludes population restoration in the absence of supplementation. Genetic diversity commensurate with the number of parental founders has been maintained in captivity. The 517 adult second-generation captive fish that spawned in Sakinaw Lake in 2011 produced a smolt emigration of almost 28,000 juvenile fish with an effective population size of 132. Allelic richness and gene diversity levels in the smolts were similar to those observed in captivity. This indicates genetic contributions from all or most founding parents have been retained both in captivity and in the nascent reintroduced natural population. [ABSTRACT FROM AUTHOR]

The lucrative returns brought by abalone fisheries have caused overexploitation and decline of the wild population. In the Philippines, the Aquaculture Department of the Southeast Asian Fisheries Development Center has successfully producedHaliotis asininaseeds in the hatchery. Aside from utilizing these seeds in aquaculture, they are also being considered for future stock enhancement endeavors of the department. This study aimed to evaluate post release behavior, recapture and growth rates of hatchery-reared abalone juveniles released in the Sagay Marine Reserve. From the two release trials conducted, results showed that abalone of shell length >3.0 cm had lower mortality during onsite acclimation and utilized transport modules as temporary shelter for a shorter period after release. Both wild and hatchery-reared abalone preferred dead branching corals with encrusting algae as their habitat. Recapture rates were comparable between the wild (7.97%) and hatchery-reared (HR2) abalone (6.47%). Monthly growth rates were almost the same between wild (0.25 cm, 4.0 g), hatchery-reared (HR1: 0.27 cm, 4.6 g; HR2: 0.35 cm, 3.8 g) abalone. Moreover, hatchery-reared abalone were recaptured up to 513 days post-release, indicating viability of released stocks in the wild. Results of releases revealed that hatchery-reared abalone can grow and survive with their wild conspecifics. [ABSTRACT FROM PUBLISHER]

The potential for restocking with hatchery organisms as a tool to rebuild depleted populations of blacklip abalone(Haliotis rubra)was investigated through replicated, control-impact studies in New South Wales, Australia. Long-term survival (>2 years) of hatchery-reared and released abalone, their impact on wild abalone abundance, and the effect of diffuse versus concentrated release was investigated on natural reefs. Long-term survival of released hatchery abalone varied between releases but averaged about that expected for wild abalone. There was no significant effect of released juveniles on the persistence or recruitment of wild abalone. Significantly greater numbers of all (released and wild) abalone persisted at release locations through time, while the total number of wild abalone increased significantly through time at release and control locations. There was no significant difference in long-term survival of abalone released in clusters of high density (2–4%) or in a diffuse or concentrated array (0–9%). These results show that restocking can supplement natural rebuilding processes of depleted wild abalone populations in New South Wales, Australia. [ABSTRACT FROM PUBLISHER]

Rigorous assessment of species and ecosystem biology underpins responsible marine stock enhancement. Estimation of limits to stocking density, based on ecosystem productivity and energetic requirements of stocked species, can be used to gauge the appropriate magnitude of release densities, minimizing waste of resources, and the possibility for adverse stocking effects. A generalized mass-balance model (generalized predatory impact model) for stocking density estimation has been developed. The approach is based around the principles of ECOPATH and accounts for dynamic estimation of stocking-related ecosystem relationships at fine temporal (days) and spatial scales. The main parameter inputs include probability distributions for key biological and life-history traits of stocked species and estimates of primary productivity for the target ecosystem. The energetic requirements of stocked fish are evaluated in terms of growth and mortality as well as ontogenetic transitions in diet, habitat use, morphology, and migration. The theoretical carrying capacity for a stocked species within a given arena is assessed from primary productivity, levels of predation by stocked fish on different trophic groups, and a specified level of acceptable trophic impact. A Monte Carlo analysis of uncertainty is used to provide a probability distribution of stocking densities for a given trophic impact. The model is applied for stocking juveniles of snook(Centropomus undecimalis)in Sarasota, FL, USA, and mulloway (Argyrosomus japonicus) in Georges River, NSW, Australia. The model is useful for estimating an appropriate stocking density when planning pilot-scale fish releases. Such releases should be carefully monitored to validate model assumptions and determine density-dependent and other environmental effects. [ABSTRACT FROM PUBLISHER]

Many declining and commercially important populations are supplemented with captive-born individuals that are intentionally released into the wild. These supplementation programs often create large numbers of offspring from relatively few breeding adults, which can have substantial population-level effects. We examined the genetic effects of supplementation on a wild population of steelhead (Oncorhynchus mykiss) from the Hood River, Oregon, by matching 12 run-years of hatchery steelhead back to their broodstock parents. We show that the effective number of breeders producing the hatchery fish (broodstock parents; Nb) was quite small (harmonic mean Nb=25 fish per brood-year vs 373 for wild fish), and was exacerbated by a high variance in broodstock reproductive success among individuals within years. The low Nb caused hatchery fish to have decreased allelic richness, increased average relatedness, more loci in linkage disequilibrium and substantial levels of genetic drift in comparison with their wild-born counterparts. We also documented a substantial Ryman-Laikre effect whereby the additional hatchery fish doubled the total number of adult fish on the spawning grounds each year, but cut the effective population size of the total population (wild and hatchery fish combined) by nearly two-thirds. We further demonstrate that the Ryman-Laikre effect is most severe in this population when (1) >10% of fish allowed onto spawning grounds are from hatcheries and (2) the hatchery fish have high reproductive success in the wild. These results emphasize the trade-offs that arise when supplementation programs attempt to balance disparate goals (increasing production while maintaining genetic diversity and fitness). [ABSTRACT FROM AUTHOR]

Aggregate hatchery production of Pacific salmon in the Kamchatka region of the Russian Federation is very low (< 0.5% of total harvest, with five hatcheries releasing approximately 41 M juvenile salmon annually), but contributions in certain rivers can be substantial. Enhancement programs in these rivers may strongly influence fitness and production of wild salmon. In this paper we document significant divergence in demographic traits in hatchery salmon populations in the Bolshaya River and we estimate the proportion of hatchery chum salmon in the total run in the Paratunka River to demonstrate the magnitude of enhancement in this system. We observed a reduction in the expression of life history types in hatchery populations (ranging from 1 to 9 types) compared to wild populations (17 types) of sockeye salmon in the Bolshaya River. We found similar trends in Chinook salmon in the same river system. This reduced life history diversity may make these fish less resilient to changes in habitat and climate. We estimate hatchery chum salmon currently contribute 17-45% to the natural spawning population in the Paratunka River. As hatchery fish increase in numbers at natural spawning sites, this hatchery production may affect wild salmon production. It is important to investigate the risk of introgression between hatchery and wild salmon that can lead to reduction in salmon fitness in Kamchatka rivers, as well as the potential of ecological interactions that can have consequences on status of wild salmon and overall salmon production in this region. [ABSTRACT FROM AUTHOR]

PCD RISK 1 is a flexible computer model designed to assist in assessment and reduction of ecological risks to natural origin fish from hatchery fish releases. PCD RISK 1 simulates predation, competition, and disease impacts on naturally produced salmonids caused by hatchery smolts in fresh water as they move downstream or residualize after release. Individual- based, the model relies upon user specified inputs of up to 45 variables, such as number and size of hatchery and wild fish, and water temperature. The model generates hatchery and natural fish of specified size distributions, then randomly pairs them for interactions for a specified number of days and encounters. Wild fish are subjected to predation if they are less than 50% the length of hatchery fish, otherwise they are subjected to competition. After all of the allowable competition and predation occurs, survivors are subjected to disease risk. The model can provide either deterministic or probabilistic output. Deterministic output includes the number and proportion of wild fish that die from predation, competition, disease, and from all interactions combined. Probabilistic output includes probability distributions of the number and proportion of mortalities, based on user-specified uncertainty input either as uniform or triangular distributions for any of several variables. If desired, the model can also quantify impacts for multiple age or size classes. Simulations of a variety of hatchery programs reveal that risks are highly diverse and that a variety of options are available to reduce risks. [ABSTRACT FROM AUTHOR]

The First Session of the Central Asian and Caucasus Regional Fisheries and Aquaculture Commission was held in Istanbul, Turkey, in the period 19-21 December 2011. The following countries attended the Meeting as members of the Commission: Armenia, Kyrgyzstan, Tajikistan and Turkey. Countries that attended the meeting as observers include: Afghanistan, Azerbaijan, Georgia, Mongolia, Ukraine and Uzbekistan. The General Fisheries Commission for the Mediterranean (GFCM) attended the meeting as observer. The Meeting, which was the Inaugural session of the Commission, adopted the Rules of Procedure of the Commission, the Financial Regulations of the Commission, the administrative budget for the first financial period, the scheme and scale of contributions to the administrative budget, a Five-year Regional Work Programme (2011 - 2015) and the acronym and logo of the Commission. The Meeting elected the chairpersons of the Commission as well as the chairperson for its Technical Advisory Committee (TAC). The Meeting also adopted the following interim scientific and technical advice: 1) Guidelines for Sturgeon Hatchery Practices and Hatchery Management for Release; 2) Recommendations of the Regional Study on the "Feasibility of Restocking and Culture-based Fisheries in Central Asia"; 3) Better Management Practices for Carp Production in Central and Eastern Europe, Caucasus and Central Asia; and 4) Conclusions and Recommendations of the Regional Workshop on Fishery and Aquaculture Statistics, Information, and Trends: Improving Data Collection, Analyses and Dissemination. [ABSTRACT FROM AUTHOR]

Rock carp Procypris rabaudi is a vulnerable endemic fish in the upper Yangtze River. Hatchery release has been carried out as a major stock enhancement strategy for this species. Ten microsatellite loci were chosen to compare genetic variation between one wild population and two hatchery groups to evaluate the potential impacts of hatchery release on the genetic structure of the wild population. Two different models indicated strong evidence of recent bottlenecks in all groups. The hatchery groups were lower in the mean number of alleles per locus, allelic richness, and allelic diversity compared with the wild population. The 80% membership coefficient indicated that 14% of the wild fish could be assigned as hybrids of wild and hatchery fish. Our results suggested that hatchery release will further reduce the natural genetic diversity in the wild population, change the genetic structure of the rock carp population, and may not benefit restoration of this vulnerable fish species. [ABSTRACT FROM AUTHOR]

surface trawl survey (2001-2005) in Penobscot Bay, Maine, U.S.A., and the nearshore Gulf of Maine waters was conducted to investigate early marine dynamics of a hatchery-dependent Atlantic salmon Salmo salar population from a severely modified river system. Data generated were used to evaluate the effect of stocking location and time on migration success and to describe the migratory pathways and environments that post-smolts traverse. Significant differences in early migration success were detected among different stocking groups, but subsequent marine survival was independent of stocking group. While the post-smolt population was primarily composed of hatchery origin smolt-stocked fish, other life-stage stocking strategies ( i.e. parr stocking) represented a higher proportion of the population than previously assumed. Catch distribution suggests evidence of an initial marine migratory pathway out of the dynamic Penobscot Bay environment. The hypothesized benefits of a predator refuge based on the co-occurring species complex is considered minimal for emigrating post-smolts given a mismatch in the size overlap among species and low abundance of other co-occurring diadromous populations. These data can be used to modify current management actions to optimize S. salar recovery and inform future research agendas. [ABSTRACT FROM AUTHOR]

The periodicity of otolith growth increments (opaque and translucent zones) from adult red snapper ( Lutjanus campechanus) was examined through a mark and recapture study (2005-2010), and laboratory holding of hatchery reared red snapper over a 2 year period (2002-2004). Wild red snapper ( n = 295) were caught hook-and-line, marked with anchor tags, injected with oxytetracycline dihydrate (OTC), and released in the Gulf of Mexico 15-40 km south of Dauphin Island, Alabama. Marked fish were recaptured up to 2.8 years after release ( n = 35) and sagittal otoliths were dissected, sectioned and examined under white and blue-violet light. The number of opaque growth zones past the OTC mark was compared to time at liberty for each fish and supported an annual periodicity of growth increment formation. Also, most (87%) of the hatchery reared fish showed two opaque zones that supported an annual increment formation rate. However, an unusual timing of opaque zone formation was shown for mark-recaptured fish. Based on known timing of OTC marking, otoliths from mark-recapture fish showed opaque zone formation from late summer (August) to early winter (December). This fall formation of opaque zones is in contrast to previous studies and its timing may relate to the end of spawning for this species. [ABSTRACT FROM AUTHOR]

The feeding and growth of hatchery-reared (HR) Japanese flounder Paralichthys olivaceus of c. 100 mm total length ( L) released off the coast of Fukushima, Japan, were investigated. From 2 to 15 days after release, the HR P. olivaceus frequently exhibited high empty-stomach frequency (>40%), low stomach-content mass (<1% of body mass), reduced somatic condition from release ( c.−10%) and negligible growth. Thereafter, empty-stomach frequency decreased, the stomach-content mass of HR fish increased to 2-8% of body mass, the somatic condition recovered and growth rate increased to 0·5-1·5 mm day. Prey items were initially mysids, shifting thereafter to fishes such as the Japanese anchovy Engraulis japonica, as observed similarly in wild counterparts. The proportion of mysids decreased with time after release irrespective of size at release, indicating the importance of mysids for adaptation to natural food. Recapture rates at age 1 year, derived from fish market surveys, varied greatly among release years (4-11%). The variation in the recapture rates was largely accounted for by the post-release growth rates ( r = 0·5), suggesting a relationship between the post-release growth of HR fish and their survival and subsequent stocking effectiveness. [ABSTRACT FROM AUTHOR]

Atlantic salmon Salmo salar in the USA have declined dramatically and their persistence is heavily dependent on stocking juvenile fish, predominantly fry. The success of stocking hatchery fry is evaluated annually throughout New England by electrofishing surveys targeting age-1 parr. The objective of this study was to examine temporal trends in Atlantic salmon parr densities throughout New England and determine how trends vary among river basins. We fit generalized additive mixed models to investigate potential linear and nonlinear temporal trends in parr density. Akaike's information criterion was used to evaluate competing hypotheses about how temporal trends vary regionally. The top-ranked model suggested two types of trends. The first type (the Penobscot River) showed a nonlinear trend in which parr densities increased until the 1990s and then rapidly decreased through 2008. The second type (all other rivers) showed a linear decrease throughout the time series. Parr density trends reflected trends in spawning escapement for each river group. We conclude that fry stocking has not been able to overcome the decrease in spawning escapement in altered stream ecosystems in New England and that additional management strategies should be considered. [ABSTRACT FROM AUTHOR]

Early marine migratory behaviour and apparent survival of hatchery-reared Seymour River steelhead (Oncorhynchus mykiss) smolts was examined over a four year period (2006-2009) to assess the impact of various management strategies on improving early marine survival. Acoustically tagged smolts were released to measure their survival using estuary and coastal marine receivers forming components of the Pacific Ocean Shelf Tracking (POST) array. Early marine survival was statistically indistinguishable between releases of summer run and winter run steelhead races, night and day releases, and groups released 10 days apart. In 2009, the survival of summer run steelhead released into the river was again trialed against groups released directly into the ocean at a distance from the river mouth. Apparent survival was improved significantly for the ocean released groups. The health and physiological status of the various release groups were monitored in years 2007-2009, and results indicate that the fish were in good health, with no clinical signs of disease at the time of release. The possibility of a disease event contributing to early marine mortality was further examined in 2009 by vaccinating half of the released fish against common fish diseases (vibriosis, furunculosis). The results suggest that marine survival may be enhanced using this approach, although not to the extent observed when the smolts were transported away from the river mouth before release. In summary, direct experimental testing of different release strategies using the POST array to measure ocean survival accelerated the scientific process by allowing rapid collection of data which enabled the rejection of several existing theories and allowed tentative identification of several new alternative approaches that might improve early marine survival of Seymour River steelhead. [ABSTRACT FROM AUTHOR]

We examined the effect of early marine entry timing and body size on the marine (smolt-to-adult) survival of Puget Sound Chinook salmon (Oncorhynchus tshawytscha). We used data from coded wire tag release groups of hatchery Chinook salmon to test whether hatchery release date, release size, and size in offshore waters in July and September influenced marine survival. Marine survival was most strongly related to the average body size in July, with larger sizes associated with higher survivals. This relationship was consistent over multiple years (1997-2002), suggesting that mortality after July is strongly size-dependent. Release size and date only slightly improved this relationship, whereas size in September showed little relationship to marine survival. Specifically, fish that experienced the highest marine survivals were released before 25 May and were larger than 17 g (or 120 mm fork length) by July. Our findings highlight the importance of local conditions in Puget Sound (Washington, USA) during the spring and summer, and suggest that declines in marine survival since the 1980s may have been caused by reductions in the quality of feeding and growing conditions during early marine life. Nous examinons les effets d'une entrée en mer hâtive et de la taille corporelle sur la survie en mer (saumoneau à adulte) chez les saumons chinook (Oncorhynchus tshawytscha) de Puget Sound. Nous avons utilisé des données provenant de groupes de saumons chinook libérés de pisciculture et marqués de fils de fer codés afin de tester si la date de libération de la pisciculture, la taille à la libération et la taille dans les eaux du large en juillet et en septembre influencent la survie en mer. La survie en mer est reliée le plus fortement à la taille corporelle moyenne en juillet et les tailles plus fortes sont associées à une survie plus grande. Cette relation s'est maintenue au cours de plusieurs années (1997-2002), ce qui laisse croire que la mortalité après le mois de juillet est fortement dépendante de la taille. L'addition de la taille à la libération et de la date de la libération n'améliore que peu la relation, alors que la taille en septembre est peu reliée à la survie en mer. Plus précisément, les poissons qui connaissent la survie en mer la meilleure sont ceux qui sont libérés avant le 25 mai et qui ont atteint une taille supérieure à 17 g (ou 120 mm de longueur à la fourche) au mois de juillet. Nos résultats soulignent l'importance des conditions locales dans Puget Sound durant le printemps et l'été et laissent croire que les déclins de la survie en mer depuis les années 1980 peuvent être dus à une réduction dans la qualité des conditions d'alimentation et de croissance durant le début de la vie en mer. [ABSTRACT FROM AUTHOR]

We recovered coded wire tags (CWTs) from a colony of Caspian terns Hydroprogne caspia on Brooks Island in San Francisco Bay, California, to evaluate predation on juvenile salmonids originating from the Sacramento and San Joaquin rivers. Subsamples of colony substrate representing 11.7% of the nesting habitat used by the terns yielded 2,079 salmonid CWTs from fish released and subsequently consumed by terns in 2008. The estimated number of CWTs deposited on the entire tern colony was 40,143 (ranging from 26,763 to 80,288), once adjustments were made to account for tag loss and the total amount of nesting habitat used by terns. Tags ingested by terns and then egested on the colony were undamaged, and the tags' complete numeric codes were still identifiable. The CWTs found on the tern colony indicated that hatchery Chinook salmon Oncorhynchus tshawytscha trucked to and released in San Pablo Bay were significantly more likely to be consumed by Caspian terns than Chinook salmon that migrated in-river to the bay; 99.7% of all tags recovered were from bay-released Chinook salmon. Of the CWTs recovered on the tern colony, 98.0% were from fall-run Chinook salmon, indicating a higher susceptibility to tern predation than for the spring run type. None of the approximately 518,000 wild Chinook salmon that were coded-wire-tagged and released in the basin were recovered on the tern colony, suggesting that the impacts on wild, U.S. Endangered Species Act-listed Chinook salmon populations were minimal in 2008. Overall, we estimate that 0.3% of the approximately 12.3 million coded-wire-tagged Chinook salmon released in the basin in 2008 were subsequently consumed by Caspian terns from the Brooks Island colony. These results indicate that CWTs implanted in juvenile salmon can be recovered from a piscivorous waterbird colony and used to evaluate smolt losses for runs that are tagged. [ABSTRACT FROM AUTHOR]

In this study, conducted over four release years, we compare the performance of hatchery steelhead Oncorhynchus mykiss that were force-released (FR) from acclimation ponds with that of fish given a 2-week volitional release (VR). After fish were released into streams, we monitored smolt out-migration travel times and survival to Lower Granite Dam on the Snake River using passive integrated transponder (PIT) tags in a subsample of each release group. To better understand the out-migration characteristics of volitionally departing fish, we also captured and PIT-tagged fish as they exited ponds in the first and last 24 h of VR. Across all release groups, travel time was 3% faster for fish that were forced from acclimation ponds than for VR groups; however, the average survival of VR groups (65.0%) was significantly higher than that of FR groups (58.6%). On average, fish that departed acclimation ponds in the first 24 h of VR took 6 d longer to reach Lower Granite Dam and had lower survival (50.3%) than those departing in the last 24 h (56.9%), though these differences were not statistically significant. We estimated smolt-to-adult survival and a stray rate index for the FR and VR groups based on recoveries of coded-wire-tagged adults. Across all releases, smolt-to-adult survival was not significantly different between groups (FR = 0.63%, VR = 0.59%), and the same was true for the stray rate index (FR = 10.9%, VR = 10.6%). Our finding that VR provided no postrelease survival benefit is consistent with the results of other published studies, but this is the first study to quantify the stray rate in relation to VR. [ABSTRACT FROM AUTHOR]

Identifying and understanding temporal genetic changes within fish populations is important for the management of these populations, especially those of conservation concern. Such changes are often the result of genetic drift, which can be exacerbated when the size of a population decreases. Using molecular-genetics techniques, we monitored nine populations of Chinook salmon Oncorhynchus tshawytscha in the Salmon River, Idaho, to determine how the genetic characteristics within and among these populations have changed over time. We found no evidence of change in the level of heterozygosity or allelic richness over three to four generations in eight of the populations. This is probably due to the fact that the populations all maintained a sufficiently large effective size, even though a few of the populations did show a decline in effective size. Also, the genetic structure among the populations did not change appreciably over time. Populations that had been supplemented with hatchery-reared fish showed genetic similarity to the within-basin hatchery source population, presumably because of the extensive use of native fish for hatchery brood stocks and minimal out-of-basin stock transfers. The lack of a detectable decline in these populations' levels of genetic diversity is encouraging, given the species' threatened status under the U.S. Endangered Species Act. [ABSTRACT FROM AUTHOR]

Burbot Lota lota in Kootenay Lake and the Kootenay River of British Columbia, Idaho, and Montana (U.S. spelling: 'Kootenai River') are at risk of demographic extinction. We conducted a pilot study to evaluate poststocking dispersal and movement of hatchery-reared, lake-strain burbot (Moyie Lake, British Columbia) in a riverine environment to determine the potential utility of this hatchery strain for future burbot rehabilitation efforts in this system. We implanted ultrasonic tags into 30 hatchery-reared burbot (ages 2 and 3) and released them into the Goat River, a tributary to the Kootenay River, in October 2009. Dispersal over a distance of 2 km from the Goat River release site to the Kootenay River occurred within 1-9 d after release (mean = 3.1 d; n = 28 active tags). Thereafter, 14 burbot remained in the Kootenay River for the rest of the 144-d study period; nine of these fish were observed moving upstream from the Goat River confluence, and five were observed both upstream and downstream from the confluence. The other 14 burbot were observed in Kootenay Lake; of these fish, eight were detected in the lake for the duration of the study, and six were observed to move regularly between the lake and the river. Dispersal distances (distance between the upstream-most and downstream-most detections per individual) within the Kootenay River ranged from 10 to 138 km (mean = 80 km), and tagged fish were detected over a 236-km reach (from 135 km downstream to 101 km upstream of the Goat River confluence). We also observed burbot in the vicinity of known spawning locations during the February spawning season. The observed dispersal suggests that a limited number of stocking locations may be sufficient to allow burbot to access available habitats within a few months postrelease. Our observations therefore suggest that lake-origin, hatchery-reared burbot may be suitable for stocking in a riverine environment. [ABSTRACT FROM AUTHOR]

Variation in the mitochondrial DNA transcriptional control region sequence was investigated in wild and hatchery-released red sea bream Pagrus major from Kagoshima Bay, where an extensive hatchery-release programme has been conducted for >30 years. The programme has successfully augmented commercial catches in the bay (released juveniles have been produced from the captive broodstock, repeatedly used over multiple generations). Samples were also obtained from outside the bay, where limited stocking has occurred. Genetic diversity indices measured as number of haplotypes, haplotype richness, haplotype diversity and nucleotide diversity were lower in hatchery-released fish than in wild fish. Genetic differences in wild fish from the bay, especially in the inner bay, compared with fish from outside the bay were detected in terms of decreased genetic diversity indices and changed haplotype frequencies. Unbiased population pair-wise F estimates based on an empirical Bayesian method, however, revealed low genetic differentiation between samples from the bay and its vicinity. Mixed stock identification analyses estimated the proportion of hatchery-released fish in wild populations in the inner and central bays at 39·0 and 8·7%, respectively, although the precision of the estimates was very low because of the small genetic differentiation between populations and relatively small sample sizes. Hence, the long-term extensive hatchery release programme has affected the genetic diversity of wild populations in the bay; however, the genetic effects were low and appeared to remain within the bay. [ABSTRACT FROM AUTHOR]

Abstract: Catch-and-release (CAR) fishing of deep-water physoclistous species can lead to increased stress and impairment often resulting in immediate release mortality. We made use of a condition index (BtR score) to evaluate the relationship between CAR-related impairment and immediate release mortality in the recreational red snapper (Lutjanus campechanus) fishery. Symptoms of barotrauma and impairment showed positive relationships with capture depth and occurred more frequently during the summer sampling than the fall. Impairment, as measured by BtR score, showed significant logistic relationships with immediate release mortality proxies such as floating and erratic swimming at release. Logistic curves had inflection points at BtR scores of 0.3–0.4 (on a scale of 0–1), above which fish experienced high immediate release mortality regardless of season (60–100%). Mean BtR scores were lower than the inflection point of the logistic curve, resulting in immediate release mortality estimates ranging from 20% to 28%. Recaptured fish showed significantly lower impairment than non-recaptured fish. The BtR score is a proficient method to estimate both impairment and immediate release mortality of red snapper in field settings. [Copyright &y& Elsevier]