Effect of allozyme heterozygosity on basal and induced levels of heat shock protein (Hsp70), in juvenile Concholepas concholepas (Mollusca)

Organisms cope physiologically with extreme temperature by producing heat shock proteins (HSPs). Expression of Hsp70 enhances thermal tolerance and represents a key strategy for ectotherms to tolerate elevated temperature in nature. Synthesis of these proteins, together with other physiological responses to elevated temperatures, increases energy demands. A positive association between multiple and single locus heterozygosity (MLH and SLH, respectively) and individual fitness has been widely demonstrated. In molluscs, MLH can decrease routine metabolic rates and improve energetic status. Juvenile Concholepas concholepas live in the intertidal zone and are constantly exposed to temperature fluctuations. Thus, these young individuals are exposed both to thermal risks and the large metabolic costs required to cope with thermal stress. We evaluated the effects of allozyme MLH and SLH on basal (control animals) and induced (stressed animals) levels of the Hsp70 in juveniles C. concholepas. Juveniles (n = 400) were acclimated at 16 °C for 2 weeks; then 100 animals were exposed to 24 °C (stress) and 100 were kept at 16 °C (control) for 2 and 7 days. The variability of 20 loci was analyzed by starch gel electrophoresis. For SLH effects we used 7 polymorphic loci. We quantified expression of Hsp70 by Western blot analyses. Hsp70 expression increased markedly (~ 90%) with temperature. We found a positive association between MLH and basal and induced levels of Hsp70 in the 2-day exposure experiment. Regardless of temperature, Hsp70 levels increased with MLH (r² = 0.7 and 0.9, for basal and induced levels, respectively) reaching maximal levels in juveniles with intermediate and high MLH levels (2 and 3 loci), and decreasing slightly (but not significantly) in juveniles with highest MLH (≥ 4 heterozygous loci). However, after 7 days of exposure to thermal stress, less heterozygous juveniles attained the same levels of Hsp70 than more heterozygous juveniles. Given the faster increment of Hsp70 in C. concholepas juveniles with intermediate-high levels of MLH, these individuals could be less affected by thermal stress in the intertidal zone. We found an association between specific loci genotype and higher Hsp70 levels (basal or induced). In comparison to homozygous juveniles, heterozygous juveniles for several loci showed higher Hsp70. However, these associations were not for the same loci in juveniles exposed to high temperature for 2 and 7 days. This suggests genotypic variation at some allozyme loci could be more important in the period of initial response to high temperature and others can be more important in the response to the chronic temperature stress.     

Coping strategies in farmed African catfish Clarias gariepinus. Does it affect their welfare?

The objective of this study was to assess whether and how coping strategies affect the welfare of African catfish Clarias gariepinus housed at low and high densities. Group composition influenced feed intake; re‐active groups (comprised of 100% re‐active fish) had a lower specific growth rate (G) and feed intake and a higher feed conversion ratio (R_FC) than pro‐active groups. Furthermore, re‐active groups had a lower energy retention than pro‐active groups. The latter was fully due to differences in feed intake, since energy partitioning (on % total gross energy intake basis) was similar among the group composition treatments. Fish held at high stocking density showed a higher R_FC and feeding speed and a lower energy retention and agonistic behaviour. None of the measured variables was influenced by the interaction effect. In mixed groups, G and number of skin lesions seemed to be affected by different behavioural phenotypes at low stocking density, but not at high density. These results indicate that both stocking density and group composition affect physical and behavioural responses of C. gariepinus. Furthermore, physical and behavioural data of individual fish housed in mixed groups suggest that coping strategy affects the fitness of different behavioural phenotypes at low, but not at high, stocking density.     

High stocking density during larviculture and effect of size and diet on production of juvenile Lophiosilurus alexandri Steindachner, 1876 (Siluriformes: Pseudopimelodidae)

Different stocking densities were investigated in larviculture and feeding of Lophiosilurus alexandri, as well as analyses of the effects on juveniles of two size‐classes and two different commercial formulated diets. The first experiment was two‐phased: (a) larvae stocked at densities of 60, 120, 180, 240, and 300 larvae L⁻¹ fed with Artemia nauplii and reared for 15 days; (b) in phase 2, densities of 5, 10, 15, 30, and 40 juveniles L⁻¹ were evaluated during feed training (20 days). Mean water temperature in both phases was 28°C. In the first phase of experiment 1, the different stocking densities did not affect fish growth or survival. In phase 2, growth was similar in all densities; however, survival was lower at higher densities. The increased density provided a rise in biomass and number of individuals produced in both phases. In the second experiment, two size‐classes of feed‐trained juveniles (30.22 ± 1.84 and 34.66 ± 2.41 mm) were given pellets of two different diameters (1.2 and 2.6 mm) for 20 days. The largest juveniles fed the 1.2 mm inert diet had higher final weights and lengths. Larviculture and feed training of L. alexandri can thus be performed successfully at high stocking densities of 300 larvae L⁻¹ during the first 15 days of feeding, and at densities of up to 40 juveniles L⁻¹ during the 20 days of feed training, respectively.     

Effects of stocking density on survival,growth and size variation of juvenile Brachymystax lenok (Pallas, 1773)

In this experiment the effects of stocking density on growth and survival of juvenile Brachymystax lenok were studied. Experimental fishes were reared at different stocking densities (5, 25, 50 and 75 fish L^?1) for 40 days at ambient temperatures (11.2–16.4°C). During the experiment, dissolved oxygen (DO) was above 5.4 mg L^?1 and other major environmental factors were controlled at the same levels in each aquarium (DO 5.4–7.2 mg L^?1, pH 6.6–7.4, and flow‐through rates 0.3–0.4 L s^?1). Mortality data in each group was recorded daily and random samples of 30 juveniles were measured and weighed every 10 days. All statistical analyses were performed by anova . The survival rate was found to be significantly affected by stocking density, but not the condition factor (CF), specific growth rate (SGR) or coefficients of variation (CV).The results demonstrate that lenok juveniles can be reared at higher stocking densities, which can increase survival under intensive conditions.     

Ocean Acidification and Increased Temperature Have Both Positive and Negative Effects on Early Ontogenetic Traits of a Rocky Shore Keystone Predator Species

The combined effect of ocean acidification and warming is expected to have significant effects on several traits of marine organisms. The gastropod Concholepas concholepas is a rocky shore keystone predator characteristic of the south-eastern Pacific coast of South America and an important natural resource exploited by small-scale artisanal fishermen along the coast of Chile and Peru. In this study, we used small juveniles of C. concholepas collected from the rocky intertidal habitats of southern Chile (39°S) to evaluate under laboratory conditions the potential consequences of projected near-future levels of ocean acidification and warming for important early ontogenetic traits. The individuals were exposed long-term (5.8 months) to contrasting pCO₂ (ca. 500 and 1400 μatm) and temperature (15 and 19°C) levels. After this period we compared body growth traits, dislodgement resistance, predator-escape response, self-righting and metabolic rates. With respect to these traits there was no evidence of a synergistic interaction between pCO₂ and temperature. Shell growth was negatively affected by high pCO₂ levels only at 15°C. High pCO₂ levels also had a negative effect on the predator-escape response. Conversely, dislodgement resistance and self-righting were positively affected by high pCO₂ levels at both temperatures. High tenacity and fast self-righting would reduce predation risk in nature and might compensate for the negative effects of high pCO₂ levels on other important defensive traits such as shell size and escape behaviour. We conclude that climate change might produce in C. concholepas positive and negative effects in physiology and behaviour. In fact, some of the behavioural responses might be a consequence of physiological effects, such as changes in chemosensory capacity (e.g. predator-escape response) or secretion of adhesive mucous (e.g. dislodgement resistance). Moreover, we conclude that positive behavioural responses may assist in the adaptation to negative physiological impacts, and that this may also be the case for other benthic organisms.     

Do stocked hatchery‐reared juveniles ecologically suppress wild juveniles in Salvelinus leucomaenis?

The dominancy of semi‐wild and hatchery‐reared white‐spotted charr Salvelinus leucomaenis juveniles was evaluated using pair‐wise enclosure tests and field stocking tests. The semi‐wild S. leucomaenis originated in a hatchery, being stocked into the test stream as eyed‐eggs. In the pair‐wise enclosure test, the semi‐wild S. leucomaenis dominated the hatchery S. leucomaenis that were of a similar standard length (L_S). The semi‐wild S. leucomaenis were subordinate to hatchery S. leucomaenis that were > 11% larger in L_S. In the field stocking test, the abundance and growth of semi‐wild S. leucomaenis was decreased in the presence of larger hatchery S. leucomaenis (14% larger L_S). Taken together, these results suggest that larger hatchery S. leucomaenis ecologically suppress the smaller semi‐wild S. leucomaenis. Salvelinus leucomaenis juveniles that are stocked with the intention of supplementing natural populations should be < 10% larger than their wild counterparts at the time of stocking to minimize their competitive advantage. The semi‐wild and hatchery S. leucomaenis used in both tests were genetically similar individuals, suggesting that the differences are due to the early rearing environment of either a natural stream or hatchery. The hatchery S. leucomaenis have lower levels of aggression as a result of selection in the hatchery rearing environment. Rearing in a natural stream from the eyed‐egg stage is likely to increase their lowered aggression.     

First evidence of natural reproduction of the Allis shad Alosa alosa in the River Rhine following re‐introduction measures

After stocking with larvae from the Gironde–Garonne–Dordogne population, in 2013, three young‐of‐the‐year Allis shad Alosa alosa, probably originating from natural reproduction, were documented for the first time in a period of nearly 100 years in the River Rhine. In 2014, a further increase was observed when 57 juveniles and eight adults were caught; seven of these eight adults were derived from stocking, indicating the success of stocking measures within the framework of the EU‐LIFE project.     

A phylogeographical analysis across three biogeographical provinces of the south-eastern Pacific: the case of the marine gastropod Concholepas concholepas

Aim The present‐day population structure of a species reflects the influence of population history as well as contemporary processes. Little is known about the mechanisms that have shaped the geographical distribution of genetic diversity in marine species present on the south‐eastern Pacific (SEP) coast. Here we provide the first comprehensive phylogeographical study of a species distributed along the SEP coast by analysing the endemic and emblematic muricid gastropod Concholepas concholepas. Location The study localities were distributed along the SEP coast ranging from Matarani (11° S) to Puerto Eden (49° S), crossing three major biogeographical provinces: Peruvian Province, Intermediate Area and Magellanic Province. Methods A total of 337 specimens of C. concholepas were collected from 14 localities in the three biogeographical provinces/areas. Mitochondrial cytochrome oxidase I (COI) gene partial sequences (658 bp) were obtained and analysed using coalescence‐based methods to infer molecular diversity and phylogeographical patterns. Results Across the 337 individuals, we found a large diversity, with a total of 179 haplotypes at the COI gene fragment. Although a slight decrease in gene diversity was observed from north to south, an analysis of molecular variance did not reveal any significant spatial population differentiation from Peru to the tip of Chile, not even across the recognized biogeographical boundaries at 30° S and 42° S. In addition, a star‐like haplotype network suggested the past occurrence of a rapid demographic and geographical expansion over the total range examined. Calculations of the onset of this expansion suggest that it might be due to climatic conditions during the period of the marine isotope stage 11 (MIS 11, 400,000 years ago), the longer and warmer interglacial episode during the Pleistocene epoch. Main conclusions Our phylogeographical analyses indicate that in the recent past C. concholepas mitochondrial DNA lineages underwent a sudden population expansion event. In addition, our data do not support the hypothesis of concordance between biogeographical barriers and phylogeographical breaks along the SEP coast. These two results are in accordance with the paradigm of high larval dispersal ability in marine species with an extended pelagic larval phase.     

Assessment of burbot Lota lota (L. 1758) population sustainability in central European reservoirs

A novel sampling scheme, using a combination of electrofishing, visual exploration by scuba divers, two types of fyke nets and longlines, was tested in four reservoirs (including their inlets and outlets) to monitor a population of burbot Lota lota. This was supplemented by fry trawling and vertical hydro‐acoustics, to detect L. lota larvae in two deep reservoirs that have had a long‐term stocking programme. The majority of the L. lota detected were juveniles, captured by electrofishing in the littoral zones of the reservoirs and in running waters. Older individuals were rarely captured with longlines or fyke nets in deeper zones or structured habitats within the reservoirs. A combination of multiple sampling methods provided an assessment of the whole population. Population establishment could not be demonstrated as the age structure of the sampled fish corresponded with that of the stocked fish. Low post‐stocking survival, migratory behaviour, interactions with other species and warmer water temperatures are considered the potential drivers for unsuccessful establishment of L. lota populations in these reservoirs.     

Estimating the stocking potential of fish in impoundments by modelling supply and steady‐state demand

1. Fish stocking is an increasingly common management tool for freshwater and marine environments and is often used to create and maintain fisheries in closed waters. The densities at which fish are stocked can have a large impact on a stocking programme’s success and sustainability. Stocking densities in impoundment sport‐fisheries, for example, are often based on social or practical factors, and ecologically based stocking models are needed to assist the selection of stocking densities that are appropriate for the environment. 2. In this study, stocking density is calculated with a numerical model that balances the supply of prey production with the energetic demand of stocked fish. The model aims to deliver outcomes over a range of potential management objectives, by providing specific consumption scenarios that represent the trade‐off between population abundance and individual body size in stocked fisheries. 3. The model uses a steady‐state population approach to calculate stocking density, which optimises population consumption by maintaining a consistent biomass distribution and encourages sustainable stocking by considering the energetic needs of all cohorts. Carrying capacity is represented by the steady‐state stocking density under a minimum consumption scenario (when fish meet only their minimum energetic needs). The comparison between a desired consumption rate and the existing level of production is used to assess the status or ‘health’ of the existing population and is used to determine whether stocking can occur and whether stocking densities can be sustainably increased. The probability of incorrectly assuming populations are achieving a given consumption level is also estimated, which is an ideal approach for interpreting multiple probability distributions. 4. A Monte‐Carlo analysis of uncertainty was used to provide a probability distribution of stocking density of Australian bass (Macquaria novemaculeata) in three Australian impoundments under various seasonal and consumption scenarios. The likely consumption rates of the existing populations were determined using historical stocking densities, which showed that the three populations were of reasonable health, although one impoundment may be overstocked. The steady‐state stocking densities depended on the desired consumption rate, and there was an eightfold difference in the stocking density aimed at providing large ‘trophy’ fish and the density required to reach carrying capacity. 5. Model outputs of existing abundance and biomass density agreed with empirical estimates of abundance and relative density in these impoundments, which provides support to the model’s accuracy. This supply–demand approach to estimating the range of appropriate stocking densities shows promise as a decision‐support tool for stocked impoundments and other closed fisheries.     

Cohort‐specific estimates of first‐year survival are positively associated with size at stocking for lake sturgeon Acipenser fulvescens (Rafinesque 1817) stocked in Black Lake,Michigan, USA

The authors conducted a gillnet survey in 2013 in Black Lake, Michigan, USA to evaluate the lake sturgeon (Acipenser fulvescens) stocking programme that began in 2001. Objectives were to (i) estimate year‐class specific abundance of juvenile lake sturgeon in Black Lake; and (ii) determine year‐class specific survival of stocked year classes and determine whether year‐class‐specific first‐year survival was related to average size at the time of stocking. Deployed were 15 and 20 cm stretch mesh gillnets at 72 randomly selected sites in Black Lake over a 3‐week survey using a Schnabel multiple‐mark, multiple‐recapture estimator to determine overall abundance of stocked fish. Ages for captured fish were determined from fin ray cross sections and the presence of coded wire tags, and apportioned the overall abundance estimate of juveniles to year class using an age‐length key. Overall survival estimates were calculated by dividing the year‐class specific abundance estimates by the number of fish stocked that year. Also evaluated was the relationship between first‐year survival and average total length (TL) at time of stocking using logistic regression. Overall survival from stocking to 2013 ranged from 0.03 to 0.53. First‐year survival was positively associated with average TL at stocking, and ranged from 0.05 for fish stocked at 9 cm TL to 0.84 for fish stocked at 22 cm TL. Estimation of future cohort‐specific abundance based on size‐based expected survival allows managers to establish annual stocking targets that should lead to the achievement of long‐term population goals for adult abundance.     

Biological control of streptococcal infection in Nile tilapia Oreochromis niloticus (Linnaeus, 1758) using filter‐feeding bivalve mussel Pilsbryoconcha exilis (Lea, 1838)

Since bivalve mussels are able to graze heavily on bacteria, in this paper it is hypothesized that when mussels are cultured with fish, the filtering efficiency of the mussels will keep the bacterial population below a certain threshold and thus assist in reducing the risk of bacterial disease outbreaks. The ability of the filter‐feeding bivalve mussel Pilsbryoconcha exilis to control Streptococcus agalactiae was tested in a laboratory‐scale tilapia culture system. Juvenile Nile tilapia (Oreochromis niloticus), the bivalve mussel as well as the bacteria were cultured at different combinations using four treatments: treatment‐1: mussel and bacteria but no fish, treatment‐2: tilapia and mussel but no bacteria, treatment‐3: tilapia and bacteria but no mussel, and treatment‐4: tilapia, mussels, and bacteria. All treatments were run in three replicates; stocking rates were 10 tilapia juveniles; five mussels; and about 3.5 × 10⁵ colony forming units (CFU) ml^?1 of bacteria in 50‐L aquaria with 40‐L volume. The mussel reduced the bacterial population by 83.6–87.1% in a 3‐week period whereas in the absence of the mussel, the bacterial counts increased by 31.5%. Oresence of the mussel also resulted in significantly higher growth and lower mortality of tilapia juveniles than when the mussel was absent. The results of this experiment suggest that the freshwater mussel P. exilis could control the population of S. agalactiae in a laboratory‐scale tilapia culture system. Future studies should focus on the dynamic interactions among fish, mussels, and bacteria as well as on how input such as feed and other organic materials affect these interactions.     

Evidence for male- and juvenile-specific contact pheromones of the common bed bug Cimex lectularius

Males and females of the common bed bug, Cimex lectularius L. (Heteroptera: Cimicidae), have been shown to produce and respond to an aggregation pheromone. We tested whether juvenile C. lectularius also produce and respond to aggregation pheromone, and whether the pheromone is perceived by contact chemoreception. In dual‐choice laboratory experiments, juveniles, but not males or females, preferred juvenile‐exposed paper discs to control discs. Unlike juveniles, males and females preferred male‐exposed paper discs to control discs. Neither juveniles, males, nor females preferred female‐exposed discs to control discs. When test stimuli were inaccessible, C. lectularius failed to show any preference. Male‐ and juvenile‐specific contact pheromones may have contrasting functions of marking shelters as safe refugia for development and growth (juveniles) or mate encounter (adults), but result in the same phenomenon, the aggregation of conspecifics.     

Recovery from a fish kill in a semi‐arid Australian river: Can stocking augment natural recruitment processes?

Localized catastrophic events can dramatically affect fish populations. Management interventions, such as stocking, are often undertaken to re‐establish populations that have experienced such events. Evaluations of the effectiveness of these interventions are required to inform future management actions. Multiple hypoxic blackwater events in 2010–2011 substantially reduced fish communities in the Edward‐Wakool river system in the southern Murray‐Darling Basin, New South Wales, Australia. These events led to extensive fish kills across large sections of the entire system following a period of prolonged drought. To expedite recovery efforts, 119 661 golden perch Macquaria ambigua and 59 088 Murray cod Maccullochella peelii fingerlings were stocked at five locations over 3 years. All fish stocked were chemically marked with calcein to enable retrospective evaluation of wild or hatchery origin. Targeted collections were undertaken 3 years post‐stocking to investigate the relative contribution of stocking efforts and recovery via natural recruitment in the system. Of the golden perch retained for annual ageing (n = 93) only nine were of an age that could have coincided with stocking activities. Of those, six were stocked. The dominant year‐class of golden perch were spawned in 2009; before the stocking programme began and prior to blackwater events. All Murray cod retained (n = 136) were of an age that coincided with stocking activities, although only eight were stocked. Among the Murray cod captured, the dominant year‐class was spawned in 2011, after the blackwater events occurred. The results from this study provide first evidence that natural spawning and recruitment, and possibly immigration, were the main drivers of golden perch and Murray cod recovery following catastrophic fish kills. Interpreted in the context of other recent examples, the collective results indicate limited benefit of stocking to existing connected populations already naturally recruiting in riverine systems.     

Effect of stocking density on growth and survival of Clarias batrachus (Linn.) larvae and fry during hatchery rearing

Experiments were conducted to determine optimum stocking density for Clarias batrachus larvae and fry during hatchery rearing. The increase in stocking density decreased the total weight, specific growth rate (SGR) and percent weight gain of Clarias larvae during a 13‐day experiment. Survival rate was highest at a stocking density of 1000 m^?2 and lowest at 5000 m^?2. Stocking density did not influence the total biomass production of larvae. Clarias batrachus fry performance was studied during a 28‐day hatchery rearing experiment whereby fry stocked at a density of 100 m^?2 attained the highest total body weight (P < 0.05). The survival rate greatly declined to 59–61% by a density increase to 300 m^?2 and above. Stocking density influenced growth and survival of C. batrachus larvae and fry during hatchery rearing. The best performance was obtained when larvae were stocked at 2000 m^?2; survival was highest with C. batrachus fry stocked at 200 m^?2.     

Lake‐specific variation in growth,migration timing and survival of juvenile sockeye salmon Oncorhynchus nerka: separating environmental from genetic influences

Time series on juvenile life‐history traits obtained from sockeye salmon Oncorhynchus nerka were analysed to assess lake‐specific environmental influences on juvenile migration timing, size and survival of fish from a common gene pool. Every year for the past two decades, O. nerka have been spawned at a hatchery facility, and the progeny released into two lakes that differ in average summer temperatures, limnological attributes and growth opportunities. Juveniles reared in the warmer, more productive Crosswind Lake were larger and heavier as smolts compared to those from the cooler, less productive Summit Lake and had higher in‐lake and subsequent marine survival. Crosswind Lake smolts migrated from the lake to sea slightly earlier in the season but the migration timing distributions overlapped considerably across years. Fry stocking density had a negative effect on smolt length for both lakes, and a negative effect on in‐lake survival in Summit Lake. Taken together, the results revealed a strong effect of lake‐rearing environment on the expression of life‐history variation in O. nerka. The stocking of these lakes each year with juveniles from a single mixed‐source population provided a large‐scale reverse common‐garden experiment, where the same gene pool was exposed to different environments, rather than the different gene pools in the same environment approach typical of evolutionary ecology studies. Other researchers are encouraged to seek and exploit similar serendipitous situations, which might allow environmental and genetic influences on ecologically important traits to be distinguished in natural or semi‐natural settings.     

A review of the world marine gastropod fishery: evolution of catches, management and the Chilean experience

Marine mollusks are among the most importantinvertebrate fisheries in the world. The mainclasses of mollusk fished are Cephalopoda,Bivalvia and Gastropoda. Marine gastropodsrepresent approximately 2% of the mollusksfished in the world. Several species ofgastropods, such as Haliotis spp., Strombus spp., Busycon spp. and Concholepas concholepas, have high economicvalue in international markets and playimportant social roles in small-scale artisanalfisheries. In the past 25 years wild-stockcatches of marine gastropods have increasedfrom 75,000 mt in 1979 to 103,000 mt in 1996.During the same period the countries involvedin gastropod landings rose from 23 to 47.Gastropods are fished mainly in: (1) theAmerican continent, dominated by the extractionof the muricid ``loco', C. concholepas, inChile and Peru; strombid conchs, Strombusspp., in the Caribbean, and abalone, Haliotis spp., in California and the west coastof the Baja California peninsula; (2) Asia andOceania, with the dominate abalone fishery,mainly in Australia and New Zealand, and thehorned turban snail, Turbo truncatus, inJapan and Korea; (3) in Africa and Europe, thedominate species extracted are Haliotismidae, heavily fished in South Africa, and thecommon periwinkle, Littorina littorea,and the whelk Buccinum undatum, which areextracted in Europe. This review summarizes the fishery of abalonespecies in California and the west coast of theBaja California peninsula. We highlightoverfishing situations and the utilization ofadaptive management tools, such as those inoperation in Baja California, where small-scalefisher associations (cooperatives) havereceived exclusive access rights to abaloneextraction within specific fishing zones, since1936. We also review the abalone fishery inAustralia, and the use of IndividualTransferable Quotas (ITQs) and Total AllowableCommercial Catches (TACC), which have been inuse since the mid-1980's. We describe thegastropod fisheries in Chile, mainly C. concholepas, highlighting their economic andsocial importance. We provide information onthe evolution of catches and exports anddiscuss the development of novel managementadaptive tools, such as the implementation ofthe Benthic Regime for Extraction andProcessing (BREP), the introduction ofNon-Transferable Individual Quotas (NTIQs) andterritorial users rights for benthic fisheries,such as the Management and Exploitation Areas(MEAS). Finally, we present and discuss thenecessary steps for the sustainable managementof marine gastropods and other benthic resources.     

The effect of stocking with 0+ year age‐class Atlantic salmon Salmo salar fry: a case study from the River Bush,Northern Ireland

An enhancement programme based on stocking 0+ year age‐class Atlantic salmon Salmo salar, conducted in the River Bush, Northern Ireland, U.K. over the period 1996–2005, was reviewed with reference to the performance and biological characteristics of wild fish. Wild ova to 0+ year fry (summer) survival was c. 8% with subsequent wild 0+ year fry‐to‐smolt survival c. 9%. Stocked unfed 0+ year juveniles gave c. 1% survival to smolt whilst fed 0+ year S. salar stocked in late summer exhibited survival at c. 5%. Stocking with unfed and fed fry contributed to increased smolt production and helped attain local management objectives between 2001 and 2005. Significant differences in biological characteristics were observed between wild and stocked‐origin fish. Wild‐smolt cohorts were dominated by 2+ year age‐class fish on the River Bush whilst smolts originating from fed fry mostly comprised younger 1+ year individuals. The mean mass of 1+ year smolts derived from stocked fed fry was significantly lower than that of wild 1+ year smolts, although these differences were not evident between older age classes. Differences in run timing between wild smolts and smolts derived from stocked fry were also apparent with the stocked‐origin fish tending to run earlier than wild fish. Although the stocking exercise was useful in terms of maximizing freshwater production, concerns over the quality of stocked‐origin recruits and the long term consequences for productivity are highlighted.     

Growth and contribution of stocked channel catfish,Ictalurus punctatus (Rafinesque, 1818): the importance of measuring post‐stocking performance

In this study it was sought to quantify post‐stocking growth, survival, and contribution of advanced size (178 mm total length [TL]) channel catfish Ictalurus punctatus fingerlings, something rarely done. Channel catfish populations were evaluated before (May 2010) and after (May to August 2011 and 2012) stocking. Relative abundance, stocking contribution, and growth were different (P < 0.05) in the two study impoundments (lakes Lone Chimney and Greenleaf, Oklahoma). For fish stocked in Lake Lone Chimney, stocking contribution was lower (3–35%), and average length and weight of stocked fish by age‐2 reached 230 mm TL and 85 g, whereas the stocking contribution (84–98%) and growth in length (340 mm TL) and weight (280 g) were higher by age‐2 in Lake Greenleaf. Given these unambiguous differences of post‐stocking performance, benchmark metrics that represent population‐level information such as relative abundance and average length and weight of the sample masked these significant differences, highlighting the importance of marking hatchery‐fish and then following them through time to determine the effectiveness of stocking. These results suggest that stock enhancement programmes would benefit from studies that quantify post‐stocking performance of hatchery fish.     

Responses of coral‐associated bacterial communities to heat stress differ with Symbiodinium type on the same coral host

This study compared the effect of heat stress on coral‐associated bacterial communities among juveniles of the coral, Acropora tenuis, hosting different Symbiodinium types. In comparison to a control temperature treatment (28 °C), we documented dramatic changes in bacterial associates on juvenile corals harbouring ITS 1 type D Symbiodinium when placed in a high (32 °C) temperature treatment. In particular, there was a marked increase in the number of retrieved Vibrio affiliated sequences, which coincided with a 44% decline in the photochemical efficiency of the D‐juveniles. Interestingly, these Vibrio sequences affiliated most closely with the coral pathogen, Vibrio coralliilyticus, which has been implicated in some coral disease outbreaks. In contrast, A. tenuis hosting ITS 1 type C1 Symbiodinium did not exhibit major bacterial shifts in the elevated temperature treatment, indicating a more stable bacterial community during thermal stress; concomitantly a decline (10%) in photochemical efficiency was minimal for this group. D juveniles that had been exposed to moderately elevated sea temperatures (30 °C) in the field before being placed in the control temperature treatment displayed a decrease in the number of Vibrio affiliated sequences and bacterial profiles shifted to become more similar to profiles of corals harbouring type C1 Symbiodinium. In combination, these results demonstrate that thermal stress can result in shifts in coral‐associated bacterial communities, which may lead to deteriorating coral health. The lower resilience of A. tenuis to thermal stress when harbouring Symbiodinium D highlights the importance of inter‐kingdom interactions among the coral host, dinoflagellate endosymbiont and bacterial associates for coral health and resilience.