Improvement on the Effectiveness of Marine Stock Enhancement in the Artificial Reef Area by a New Cage-Based Release Technique

The release technique,affecting the survival rate of fish species released for stock enhancement,plays a vital role in the effectiveness of the enhancement.In order to improve the probability of released fish settling down to bottom,a new cage-based release technique was designed and tested via a water tank with artificial reef models.Two coral reef fish species,Sebastes schlegelii and Paralichthys olivaceus were assessed using this technique.Fish behavior and distribution in water tank were recorded and compared with the traditional release release techniques.Results showed that in the case of cage-based release technique:1)when the release process is just finished,the distribution index(DI)of juveniles S.schlegelii and P.olivaceus were 97.8%and 98.9%at reef area,40%and 71.1%at release point,respectively,which was higher than those using two alternative techniques;2)its impact duration was less than that in the other two conditions,where the DI within 4 hours was higher after releasing,especially for S.schiegelii.These findings indicated that the new cage-based technique could release the fish into the specified location,and has a potential to mitigate the stress reaction of fish caused by releasing process.

Parentage determination of black sea bream(Acanthopagrus schlegelii)for stock enhancement:effectiveness and loss of genetic variation

The stock enhancement programs for black sea bream Acanthopagrus schlegelii have been conducted in China for a fewyears.However,little information has been reported concerning the effectiveness and genetic effect of black sea bream stock enhancement.In order to detect the contribution of released individuals in Zhujiang River Estuary(ZRE)and Daya Bay(DB),six microsatellite markers were used to identify the hatchery-released individuals.In addition,this pedigree of hatchery populations(broodfish and hatchery-released offspring)was traced to detect the number of effective parents(N_(e)),the inbreeding coefficient and the decrease of genetic variability in the reproduction.The pedigree reconstruction showed that at least 69(out of 93)broodfish had offspring.The estimated N_(e) was 54.8,consequently the inbreeding coefficient was 0.91%.The genetic diversity of hatchery-released offspring was lower than that in that of broodfish(heterozygosity alleles,0.727-0.774),some alleles(number of alleles,61-69)and genetic variance were lost during reproduction.It was observed that wild samples had higher levels of genetic diversity compared with hatchery populations as well as recaptured samples in releasing area.A total of 128 hatchery-released black sea bream were identified among 487 recaptured samples in ZRE,while a total of 15 samples were identified among 96 samples in DB.In summary,there was a high survival of released fish.N_(e)vertheless,the results provided evidence to consider a loss of genetic variation in hatcheryreleased stock and a negative genetic effect of the stock enhancement.

Recommendations for Development of Stock Enhancement Fishery in China

In 2011,China put the stock enhancement fishery in the same place as aquaculture,fishing,aquatic product processing and circulation industry,and recreational fishery,i. e. one of the five pillar industries of fishery economy. Developing the stock enhancement fishery is a strategic measure for restoring and protecting fishery resources,expanding fishery,replacement environment cost,and promoting sustainable development of fishery. At present,cultivation and development of the new rising industry,the stock enhancement fishery,has certain comparative edge,excellent economic foundation and broad development space in China.

Exposure of silver carp (Hypophthalmichthys molitrix) to environmentally relevant levels of cadmium:hematology,muscle physiology,and implications for stock enhancement in the Xiangjiang River (Hunan,China)

Cadmium is a non-essential metal with a wide distribution that has severe toxic effects on aquatic animals. Changes in hematology and muscle physiology were examined in silver carp (Hypophthalmichthys molitrix) exposed to environmentally relevant levels of cadmium (0.01 mg L-1 ) for 96 h. Cadmium exposure induced significant increases in the red blood cell count, and in the plasma concentrations of cortisol, glucose, and lactate. This suggests that the dose of cadmium was sufficient to cause stress, possibly associated with impaired gas exchange at the gills. There were no changes in hemoglobin concentration or plasma protein concentration. Significant decreases in muscle energy fuels (ATP and glycogen), and increases in muscle lactate persisted until the end of the exposure period, respectively. The changes in muscle lactate and protein in silver carp differed from those observed in response to exposure of fish to cadmium and heavy metals in other studies. The study highlights the importance of selecting unpolluted release sites with suitable water conditions for the survival of newly released individuals for stock enhancement of the Xiangjiang River.

Maximum sustainable yield estimation of enhancement species with the characteristics of movement inside and outside marine ranching

Marine ranching can be regarded as a type of artificial fishery,and its construction aims at the sustainable utilisation of fishery resources.Therefore,the sustainable yield level of target species in marine ranching has become one of the concerns of stakeholders.The enhancement surplus production model proposed by Wang(2021)based on the traditional surplus production model can be used to assess the sustainable utilisation of settled species in marine ranches.However,when the target species has the characteristics of migration inside and outside marine ranches,its sustainability assessment will be aff ected.Based on the movement range and resource density levels of enhancement species inside and outside marine ranches,we built a biomass change model that is suitable for enhancement species with migration characteristics inside and outside marine ranches(migration enhancement biomass model).Moreover,we simulated the effects of factors,such as the ratio of the movement range and the ratio of resource density within and outside marine ranches and the fishing strategy for the enhancement species in marine ranches,on the estimation of maximum sustainable yield(MSY).Results show that the large movement range of enhancement species outside marine ranches was associated with the obvious advantage of the proposed migration enhancement model over the traditional enhancement production model.A small difference in the densities of enhancement species inside and outside marine ranches was highly beneficial for improving the accuracy of MSY estimation.The migration enhancement biomass model proposed in this study provides an idea for estimating the MSY of an enhancement species that migrates inside and outside marine ranches.Researchers can adjust the parameters of the model in accordance with the actual situation of resource distribution and changes to improve the scientificity of fishery stock assessment.

Research in migration route of hatchery released Chinese shrimp(Fenneropenaeus chinensis) in the Bohai Bay using method of SSR marker

This study provides new insights for the hatchery released Chinese shrimp(Fenneropenaeus chinensis),including proportion,dynamic migration route,after they were released into nature for stock enhancement using a new strategy quite different than ever.Chinese shrimp were sampled at 22 survey stations during two investigation voyages acrossing 74 survey stations in the Bohai Sea from July 16 to August 9 in 2015.Among 289 sampled individuals during the second voyage,totally 155 shrimps were identified as hatchery shrimp released into the Laizhou Bay at mid-May in 2015 based on finger-print of eight SSR(simple sequence repeats)markers,and the proportion of hatchery released shrimp in recapture samples were from 41.30%–85.71%in each station with an average value 53.63%,which verified a previous view point that up to 90%of autumn season Chinese shrimp landing in the Bohai Sea were composed of hatchery released.Meanwhile,the dynamic migration route of hatchery released shrimp revealed that part of released shrimp migrated heading northwest along the west coast of the Bohai Sea up to the Bohai Bay but just remained at the Laizhou Bay until over-wintering migration at midOctober when they initiate over-wintering migration.Present unnatural spring season shrimp fishing model cut the throat of spawner shrimp chance to swim back to their respective spawning plants at each spring,it still no chance to clarify whether the hatchery released shrimp could replenish to the reproduce population and complete a whole life cycle as same as their natural relatives.

Progress on Research and Construction of Marine Ranching along the Coast of Shandong Province of China

As a new fishery mode of low-carbon economy, marine ranching has played an important role in promoting sustainable development of fishery and construction of ocean economic zone in China. Since the year of 2000, environment improvement, stock enhancement and mariculture development have been given very high degree of importance along the coast of Shandong Province of China. Studies and tests on artificial reefs and marine ranching, including effect investigation of artificial reefs set up in Jiaonan coastal areas in 1980s, hydrodynamic characteristics experiment of artificial reef, study on material and configuration of artificial reef models, algae transplantation and seaweed beds construction, stock enhancement and releasing etc., have been carried out in recent years. Furthermore, the Restoration Plan of Fishery Resources of Shandong Province has been implemented since the year of 2005, which greatly boosted the construction of artificial reefs and marine ranching along the coast of Shandong. By June of 2010, the total investment on the construction of artificial reefs and marine ranching is over $77 million USD. One hundred artificial reef districts, with total area about 33,350,000 m2 have been set up. The construction of marine ranching along the coast of Shandong Province has been in certain scale and the economic, social and ecological effects are obvious.

Survival of Red King Crab （Paralithodes Camtschaticus） Juveniles on Natural and Artificial Substrates

Understanding settlement tendencies and substrate preference is essential for king crab stock enhancement because structurally complex habitats provide red king crab juveniles with shelter and protect them from predation and cannibalism during critical stages of their lives. The growth and survival rates of juvenile red king crab （Paralithodes carntschaticus） from the first juvenile instar stage after settlement from the free-swimming glaucothoe （stage C 1）, to the third juvenile instar （stage C3）, that were reared in aquaria with natural rock, shell, and artificial substrate from June 8 to July 15, 2008 at the Alutiiq Pride Shellfish Hatchery in Seward Alaska were evaluated. The percent of crabs surviving to the C3 juvenile stage was the highest （34%） for the artificial substrate, the lowest （24%） for the shell substrate, and intermediate （27%） for the rock substrate. No significant differences were found in the wet weight and carapace width （P〉0.05） among these three treatments, although the crabs were reared in the natural shell substrate, were heavier, （4.1±0.3 mg） than those reared in the natural rock （3.9±0.1 mg）, and artificial substrates （3.8±0.7 mg） and crabs reared in the natural rock substrate were larger （1.8±0.2 mm） than those reared in the natural shell （1.7±0.2 mm）, and the same as those in the artificial substrates （1.8±0.2 mm）. These results may be due to the short length of the experiment relative to the life cycle of the species. Further research is needed to understand the optimal environmental conditions for juvenile crabs and determine how their crucial habitats, which may be easily disturbed by human activities, can be conserved.

Cryptic Behaviour of Juvenile Turbot Psetta maxima L.and European Flounder Platichthys flesus L.

The aim of this study was to examine the burying behaviour of hatchery-reared European flounder Platichthys flesus and turbot Psetta maxima, and whether conditioning on a sandy substrate would improve burying efficiency. Both species buried shortly after release on a sandy substrate. However, the study revealed interspecies differences;the flounder buried immediately after release, while the turbot buried gradually. No significant difference in burying efficiency was observed between na&iumlve and conditioned flounder and turbot. An effect of size on burial efficiency was observed for both flounder and turbot with a tendency for larger fish to bury more efficiently than smaller fish, despite previous conditioning. Size at settlement was found to be >2 cm for flounder and >3 cm for turbot.