Evaluation of Commercial‐scale Approaches for Cryopreservation of White Crappie,Pomoxis annularis,Sperm

Crappie, Pomoxis spp., are popular game fish throughout North America and are produced by public and private hatcheries. However, production is limited by a lack of information on tank culture and induced spawning methods. Development of techniques for storage of sperm and in vitro fertilization would increase flexibility in spawning. Therefore, techniques for sperm cryopreservation were examined in white crappie, Pomoxis annularis. Sperm from adult wild white crappie were used to evaluate sperm extender, cryoprotectant agent and concentration, and cooling technique based on post‐thaw sperm motility. Percent egg fertilization was also compared between sperm stored in the two best cryopreservation protocols and two different osmotic activator solutions. Sperm were cryopreserved using treatment combinations of two extenders (350 mOsmol/kg Hanks' balanced salt solution [HBSS] and 350 mOsmol/kg Ca²⁺free HBSS) and two cryoprotectants (dimethyl sulfoxide [DMSO] and methanol) at concentrations of 5, 10, and 15% that were cooled at four different rates: 5, 10, 20, and 40 C/min. Post‐thaw sperm motility and fertilization rates indicated white crappie sperm can be cryopreserved using either extender, cryoprotectants of either 5% DMSO or 10% methanol, and cooling at 40 C/min. A follow‐up experiment demonstrated sperm in suspensions on ice retained viability after overnight transport.     

Induced spawning, larval development and rearing of two indigenous Malaysian mahseer, Tor tambroides and T. douronensis

The Mahseers (Tor spp.) are highly valued freshwater fishes across the Himalayan and South‐east Asian regions. Over exploitation of natural stocks because of high demand and the deteriorating environmental conditions have resulted in marked decline of mahseers in the wild. Malaysian mahseers, T. tambroides (Bleeker) and T. douronensis (Valenciennes), locally known as empurau, kelah or belian and semah, respectively, have significant cultural and economic importance but both species are now threatened in the wild because of environmental degradation and over fishing. A captive breeding programme was instigated to attempt to propagate these two species artificially for conservation and aquaculture purposes. Both pond‐reared and tank‐held T. tambroides and T. douronensis reached sexual maturity in captivity and were successfully induced to spawn using hormone treatments. Ovaprim (0.5 mL kg^?1) was the most successful hormone treatment for both species. Pre‐treatment of fish with Ovaplant (28–68 μg kg^?1, 2–7 weeks before spawning induction) greatly improved the success rate of spawning induction. Repeat spawning (within 4 months of initial spawning) was induced in some captive fish. Use of formalin baths improved hatching by preventing fungal infections. Embryonic development and hatching are described. Juveniles were reared in static greenwater ponds. Tor tambroides reached 142–179 g (max 270 g) in 60 weeks. These results represent the first successful captive spawning and rearing of both species. Options for future research to improve production are discussed.     

Captive spawning and larval rearing of California yellowtail (Seriola lalandi)

A captive population of California yellowtail (Seriola lalandi) was used to document spawning patterns, including measures of egg production, population fecundity and egg and larval quality from 2007 to 2010. Spawned eggs were also used to document larval development and to develop rearing techniques for aquaculture in the region. Broodstock growth and condition factor were best when feeding rations were maintained at 10–15% body weight week^?1 during the warm summer months. A winter ration based on satiation feeding was typically 4% body weight week^?1. During the 4‐year study period, the only broodstock health issue was an infestation by the parasitic gill fluke Zeuxapta seriolae, which was readily treated. Spawning occurred naturally in the 140 m³ tank when the ambient water temperature reached 16°C and ended when the temperature exceeded 22°C. Egg production reached a maximum in 2010 when 43 spawn events were recorded from a pool of nine females yielding 36.8 million eggs in total. The average female size at this time was 20 kg, which equated to a total annual population fecundity of approximately 226 000 eggs kg^?1 female year^?1. Larval rearing trials yielded survival rates as high as 5.8% from egg to 50 days post‐hatch (dph). Successful larval culture methods included the addition of algae paste for green water culture, rotifers (20 rotifers mL^?1) at 2 dph and Artemia (5 Artemia mL^?1) at 6 dph. Larvae were transferred from the incubation tank at 10 dph to a shallower tank with 33% greater surface area to accommodate the larvae's strong orientation to surface waters. This research represents the first documentation of successful spawning and larval rearing for S. lalandi in the eastern Pacific.     

Fathead minnow reproduction: Implications for commercial culture

The fathead minnow, Pimephales promelas, is widely used as a bait, forage, and research fish in the United States. A hardy and fecund fish, this species has many attributes that are excellent for culture. Unfortunately, despite the widespread use of fathead minnows in toxicity testing and thousands of resulting publications, relatively little aquaculture‐related research has been conducted in support of commercial production. On the surface, current commercial fathead minnow production practices appear much the same as those of a decade ago. However, producers continue to refine culture methods, balancing broodfish stocking rates, spawning substrate quantity, and feeding rates in an attempt to meet both losses to predators and market demand. This review examines relevant reproduction‐related studies in the fields of ecology, behavior, toxicology, and aquaculture with the goal of advancing fathead minnow culture. In fathead minnow production, relative to the culture of food fish species, reproduction is vital, more so than rapid growth or a low feed conversion ratio. Fish numbers may exceed 1 million fish/ha, while feeding rates are relatively low and in feeder fish production, growth is deliberately restrained in order to maintain fish within market sizes year‐round. Underappreciated factors identified as affecting reproduction and with implications for commercial culture include: (a) poor egg adhesion to commonly used spawning substrates, (b) egg and fry cannibalism at high fish densities, and (c) the relatively short breeding period of individual males. Results highlight the importance of selecting an appropriate broodfish stocking rate based on fish size, anticipated pond fertility, and feeding program. New methods to improve reproductive performance will likely increase costs and will need to be accompanied by thorough economic analyses.     

Use of an acoustic telemetry array for fine scale fish behaviour assessment of captive Paiche,Arapaima gigas,breeders

As Arapaima gigas is one of the most valuable species for the growing production of Amazonian aquaculture, knowledge of its reproductive behaviour and its application to increase reproduction success in captivity is of great importance as no hormonal spawning induction technique exists for this species. An acoustic positioning system (LOTEK Inc.) was used to observe the interactions of adult fish to better understand the formation of mating pairs. Fish were placed in a 4,500 m² aquaculture pond over a 6‐month period in the IIAP field station of Pucallpa, Perú. This paper describes the methodological protocols used to set up and test the hydrophone array and presents the methodology used for the analysis of the huge amount of collected data. This methodology is illustrated by the analysis of a 6‐day period for a mating pair that showed a spawning event. The results indicated that male and female occupied mostly one preferential area in one pond edge where the nesting area is located. Different activity patterns were observed during the spawning event, with male and female being closer during the spawning day. The results also showed that male travelled less distance than female during the studied period. Finally these results demonstrated the suitability of such equipment to monitor fish interactions at fine spatial (sub meter) and temporal (5 s) scales in confined environments like aquaculture ponds.     

Environmentally conditioned,year‐round volitional spawning of cobia (Rachycentron canadum) in broodstock maturation systems

Year‐round control of the spawning cycle of cobia (Rachycentron canadum) has been established by using water temperature manipulation. To compare the effectiveness of using this method to induce volitional spawning in cobia, two 80 m³ recirculating aquaculture systems (RAS) were used. Temperatures in one of the maturation tanks (‘Mat 1’) were maintained between 27 and 29°C for 12 months of the 15.5‐month study period. Temperatures in the second maturation tank (‘Mat 2’) were allowed to fluctuate naturally throughout the year and ranged from 20 to 32°C. A total of 101 spawning events occurred in the tanks between the spring of 2008 and the summer of 2009 (3 April 2008 to 17 June 2009). Of the 38 total spawning events in Mat 1, 17 of them (44.7% of all Mat 1 spawning events) occurred during the off‐season (fall and winter). The egg viability rates did not differ significantly (P > 0.05) between on‐ and off‐season spawns in Mat 1. Conversely, cobia broodstock exposed to natural water temperatures (no environmental manipulation) in Mat 2 followed the natural pattern of warm water (>26°C) dependence, limiting egg production to spring and summer seasons. This method of water temperature manipulation allows for effective control of the cobia reproductive cycle without compromising egg viability.     

Pagellus erythrinus (Common Pandora): A Promising Candidate Species for Enlarging the Diversity of Aquaculture Production

The euryhaline species Pagellus erythrinus was investigated for potential use in aquaculture. The research focused on the biological aspects of the species examining its adaptability in captivity, examining reproduction, brood stock construction, larval rearing and on-growing of the fingerlings, produced in cage culture under different diets and feeding regimes. Natural spawning resulted in the production of 150,000 viable eggs/kg with an average hatching rate of 85%, whereas spawning induced with injection of HCG hormone (500 and 250 IU/kg) produced 16,140 and 29,940 viable eggs/kg for the high and low dosage, respectively, with an average hatching rate of 75%. The culture of the fingerlings in floating cages in the region of Galaxidi (east central Greece) is also described. The results are encouraging in terms of a possible intensive culture of the species, but nonetheless further research on the reproduction and the larval rearing of the species is imperative.     

Controlled reproduction in Anguilla anguilla (L.): comparison between spontaneous spawning and stripping‐insemination approaches

This study aimed to compare the fertility of eggs between artificially matured female silver eels that spawned spontaneously and those that were spawned by manual stripping. The effects of the two methods of spawning on ovulation and fertilization rate were also investigated. For this purpose, 18 wild female European eels captured in Bonello lagoon (North Adriatic Sea) were carp pituitary extract‐injected to undergo sexual maturation and ovulation; a final injection of 17,20β‐dihydroxy‐4‐pregnen‐3‐one (DHP) was administered when at least 30% of the oocytes were fully transparent. After the DHP‐injection, nine eels were transferred to a new closed recirculating aquaculture system, where they were housed with spermiating males (sex ratio 4/1) to allow spontaneous spawning (SPT‐group); the remaining nine eels were transferred to a 250 L tank and ovulation was checked at four‐hourly intervals by manual stripping (STR‐group). The number of eggs per female in the SPT‐group was significantly greater than that in the STR‐group. Furthermore, fertilization rates in the SPT‐group were notably higher than those observed in the STR‐group. Significantly, the best performances were obtained among eels in which at least 50% of oocytes were fully transparent at the time DHP was administered. We conclude that the fertility of eggs from spontaneously spawning eels is superior to that of eggs acquired by strip‐spawning and artificial fertilization.     

Review of Aquaculture Research and Development of the Australian Freshwater Fish Silver Perch,Bidyanus bidyanus

Silver perch, Bidyanus bidyanus (Mitchell), is a freshwater fish that is endemic to the Murray‐Darling River System, Australia. Over recent decades, its distribution and abundance in the wild have declined, and it is now a threatened species with the conservation status of “vulnerable.” Silver perch is a schooling, omnivorous fish, with white flesh, few bones, and high levels of omega fatty acids, and its aquaculture potential has long been recognized. Hatchery techniques, based on hormone‐induced spawning of captive broodfish in tanks and rearing of larvae in fertilized earthen ponds, were developed in the early 1980s. Fingerlings are currently used for stock enhancement and conservation or sold for commercial grow‐out or stocking farm dams. Research into the grow‐out of silver perch commenced in 1990 and demonstrated that it is an excellent fish for culture in static aerated earthen ponds with high survival rates (>90%), fast growth rates (2–5 g/fish/d) at high stocking densities (20,000/ha) leading to high production rates (10 tonnes/ha/yr). Since 1996, there has been research into nutrition, diet development, feeding strategies, broodfish domestication and management, culture in tanks and tank‐based recirculating aquaculture systems, diseases, health management, genetic improvement, and cage culture. Silver perch is a hardy species that performs well under different culture conditions and on diets with no or low levels of fish meal. Technology has been transferred to industry through major conferences in 1994 and 2003 as well as workshops, field days, extension, seminars, and numerous scientific and technical publications. The high quality of silver perch and its excellent culture attributes suggest that the species has the potential to form a large industry based on high‐volume, low‐cost production. However, despite these features and a strong technical base provided by research and development, industry growth has been limited and a relatively small industry currently produces only around 500 tonnes annually. Development has been restricted by a number of factors: poor site selection and design of some farms; use of inappropriate husbandry and/or production strategies; difficulties with pond production, including significant losses to bird predation and diseases; high costs of feeds; limited marketing and promotion; no processing component; no large‐scale investment; and the failure of many farms that were too small to be economically viable. Recent research has found that silver perch performs well in cages (high survival [>90%], good growth [1.7–3.5 g/fish/d], and high production rates [50–90 kg/m³]), and cage culture has advantages such as ease of management and prevention of bird predation that may help overcome some of the problems associated with pond production. Improved health management, new production strategies, cage culture, use of interstrain hybrids and other genetically improved fish, and integration with cotton and other irrigation industries offer opportunities for increased production and efficiencies, and further development of the silver perch industry. The potential of silver perch for commercial aquaculture remains very high.     

Age-specific patterns in density-dependent growth of white crappie, Pomoxis annularis

The relationship between growth in white crappie, Pomoxis annularis Rafinesque, and climate, lake morphometry and population density was studied in 103 Texas reservoirs. Growth of age‐0 through age‐3 white crappie was significantly (P≤0.05) related to latitude, growing season and surface area. Growth of age‐1 through age‐5 white crappie also was related to annual precipitation. Multiple linear regression models with precipitation and mean catch per unit effort (CPUE) of white crappie as independent variables explained 14–22% of the variation in growth of age‐0, ‐1 and ‐2 white crappie. By contrast, growth of age‐3, ‐4 and ‐5 white crappie was unrelated to CPUE. Apparently, between age 2 and 3, the density of white crappie in Texas reservoirs falls below a density‐dependent growth threshold beyond which growth is no longer related to density. This density‐dependent threshold was most likely related to angler harvest of larger, older white crappie.     

Broodstock spawning and larviculture of whiting (Merlangius merlangus L.) reared in captivity

In recent years, an increasing interest in the farming of marine ‘white’ fish, such as cod, has been observed in the aquaculture industry. One species being considered for aquaculture development is whiting (Merlangius merlangus L.). With little data being available on the domestication of this species, our study aimed to characterize spawning behaviour and rhythmicity in captive broodstock and provide original data on egg incubation, embryonic development and larval rearing. The results observed through video recording showed that spawning mainly occurred at night with active courtship behaviour. Daily egg batches were collected from two separate spawning seasons, with an average fertilization success declining from 77% to 53%. Time to hatch was inversely related to the incubation temperature and occurred after 78 degree‐days (9 days at 8 °C), with emerging larvae ranging in size from 3.3 to 3.46 mm total length and hatch success ranging from 48.3% to 99.9%. In comparison with a clear water environment, a green water regime during the first days of larval rearing significantly improved larval growth and survival. These results are the first to describe spawning activity, early development and larval performances in whiting and are promising for the potential future development of whiting aquaculture.     

Conditioning,maturation and year‐round natural spawning of orange‐spotted grouper,Epinephelus coioides (Hamilton, 1822), in recirculating aquaculture system

The present experiment was aimed at studying the conditioning, maturation and natural spawning of orange‐spotted grouper, Epinephelus coioides, in a recirculatory aquaculture system (RAS). Thirty fish (n = 30; 3.35 ± 0.05 kg) were stocked in a circular tank of 125 m³ capacity fitted with an RAS for conditioning and broodstock development. After 15 days, 15 fish were implanted with 17 α methyl testosterone and letrozole at the rate of 5 mg and 0.2 mg/kg body weight, respectively, for conversion from female to male. The gonadal development started after 1 month, and by 90th day, 63.53 ± 3.78% and 2.07 ± 0.84% of the oocytes attained a size of 400–500 μm and 500–600 μm respectively. Natural spawning commenced in the RAS from 4th month onward after stocking and spawning continued round the year. The spawning pair showed courtship behaviour with a typical vertical burst of swimming just before release of gametes. The total number of eggs spawned during 1 year was 47.23 million with spawning frequency varying form 5 to 13 times per month. The association of spawning events with new moon day (lunar cycle) weakened as time progressed. The mean monthly fertilization and hatching rates varied from 77.80 ± 3.34% to 83.70 ± 1.76% and 82.80 ± 4.21% to 88.33 ± 1.39% respectively. The study proved that RAS is an efficient system that provides a stable, controllable and conducive environment for year‐round natural breeding of orange‐spotted grouper.     

Completion of the Pacific bluefin tuna Thunnus orientalis (Temminck et Schlegel) life cycle

Tuna aquaculture is currently dependent on the wild capture of juveniles for production. The development of hatchery technology for bluefin and other tunas would be a major step forward in improving sustainability of their aquaculture. The present study overviews the technology in the life cycle completion of the Pacific bluefin tuna (PBT) Thunnus orientalis (Temminck et Schlegel) under aquaculture conditions in Kinki University, and the problems to be solved for the establishment of tuna hatchery technology. On 23 June 2002, broodstock of PBT that were artificially hatched and reared spontaneously spawned in captivity. The resulting eggs hatched and were subsequently reared to the juvenile stage. The spawning fish were the result of a research project started in 1987 to rear wild‐caught juvenile PBT that were several months old. Fertilized eggs were obtained from these fish in 1995 and 1996. Resulting juveniles (the artificially hatched first generation) were reared to maturity and spawned in 2002. Over the summer of 2002, 1.63 million eggs from these fish were used for a mass rearing experiment, and 17 307 juveniles were produced and transferred to an open sea net cage. Of these artificially hatched second‐generation PBT, 1100 grew to approximately 95 cm total length and 14 kg body weight in 22 months. This procedure means the completion of PBT life cycle under aquaculture conditions, which was first attained among large tuna species. The problems awaiting solution in PBT hatchery production are their unpredictable spawning in captivity, to improve survival during the first 10 days post hatch, to reduce cannibalism in larval and juvenile stages, and to solve collision problem causing high mortality during the juvenile stage.     

Design and performance of a recirculating aquaculture system for oyster larval culture

The major objective of this study was to introduce a newly designed recirculating aquaculture system (RAS) for oyster (Crassostrea angulata) larval culture. The system includes a culture tank, a suspended circular inlet‐pipe, an upwelling aeration pipe, combined “banjo” sieves and a bioreactor chamber containing microalgae life keeping installation. The system was designed to resolve three problems: (i) stranding of larvae caused by water level changes and aeration, (ii) physical clogging of the screens and also (iii) deterioration of diet microalgae. The culture tank, “banjo” sieve size, water flow rate and light intensity for maintaining microalgae activity were all designed according to the pattern of larval movement and feeding behaviour. Results of this study showed the best average SGR for larval length was 6.36%/d (9.5 μm/d) and survival rate was 80%, with initial rearing density of 50 larvae/ml, indicating the problems above were fully resolved. Consequently, the system is fit for larval culture in mass production of oysters.     

Evaluating spawning performance among captive Florida pompano Trachinotus carolinus broodstock using microsatellite‐based parentage assignment

Florida pompano has been identified as a promising candidate for commercial‐scale aquaculture production, but to date, little information is available regarding captive broodstock spawning characteristics. Genetic markers were tested for their power in monitoring mating outcomes and potential in analysing heritability of rapid growth trait in Trachinotus carolinus. A total of 20 unrelated adults (10 females and 10 males) were chosen for a hormone‐induced mass spawning event. The 515 fastest growing and 485 slowest growing fish of the total 4852 offspring were considered a selected progeny stock, and fish were collected at 45 days post hatch based on their growth traits. Parentage analyses based on the 20 breeders and 1,000 selected progeny were performed using a total of nine microsatellite markers, a 100% assignment rate was achieved, and a four‐marker set was the minimum number for the parentage assignment. The effective breeding number for the selected progeny was 11 (six females and five males), among which three females and two males were predominant contributors with the total contribution of 95.8% and 94.7% respectively. The proportion of fast‐growing offspring from broodfish and each mating cross (sire/dam) was used for detecting whether variation in growth of the offspring was related to parental stocks. Results showed that three adults and their mated combination exhibited the greatest fast‐growing offspring proportion (69.73% and 55.95%). This research provided new information regarding spawning performance and parental contribution during mass spawning events; both important first steps towards developing improved management strategies for captive Florida pompano broodstock.     

Dietary fatty acid enrichment during the spawning season increases egg viability and quality in Hippocampus hippocampus

Control of the reproductive cycle is essential to achieve a successful aquaculture industry. Seahorse reared in captivity often shows eggs of poor quality and low offspring survival due to unsuitable rearing and nutritional protocols. This study aimed to evaluate the effect of dietary enrichment, added exclusively during the spawning season, on the egg quality of Hippocampus hippocampus. The effect of enriching mysis throughout the spawning season was analysed in terms of female fecundity, egg viability, egg size and fatty acid profile. The results showed that fecundity was not affected by the enrichment of the diet, but egg viability was increased when females were fed the enriched mysis (84.9 ± 4.1% compared to 62.2 ± 9.4%). Moreover, the content of several PUFA (20:4n‐6, 18:2n‐6, 22:5n‐3, 22:5n‐6, sum of n‐6) decreased throughout the spawning season, especially in the last clutch, in eggs originated from females fed non‐enriched mysis. Eggs from females fed the enriched diet maintained the fatty acid profile throughout the spawning season. In conclusion, enrichment of the diet of H. hippocampus improved egg viability and avoided a decrease in the quality of eggs by maintaining PUFA content in the last clutches of the spawning season.     

Toxicity of Peracetic Acid to Fish: Variation among Species and Impact of Water Chemistry

There has been strong interest in the use of peracetic acid (PAA) in aquaculture as it can be used to disinfect water and hard surfaces and thereby eliminate or lower the burden of fish pathogens. Unfortunately, there has been little research on the toxicity of PAA to fish. Twelve species of fingerling fish that are important to aquaculture were exposed to PAA for 24 h in static toxicity bioassays in well water. These fish were: fathead minnow, Pimephales promelas; black‐nose crappie, Pomoxis nigromaculatus; bluegill, Lepomis macrochirus; blue tilapia, Oreochromis aureus; channel catfish, Ictalurus punctatus; golden shiner, Notemigonus crysoleucas; goldfish, Carassius auratus; grass carp, Ctenopharyngodon idella; largemouth bass, Micropterus salmoides; rainbow trout, Oncorhynchus mykiss; sunshine bass, Morone chrysops × M. saxatilis; and walleye, Sander vitreus. Median lethal concentration (LC₅₀) values were estimated with the trimmed Spearman–Karber method using nominal PAA concentrations. The mean 24‐h LC₅₀ values ranged from 2.8 to 9.3 mg/L PAA. Fathead minnow were very sensitive and blue tilapia were very tolerant to PAA exposure; LC₅₀ values of other species tested were within the range of 4.1–6.2 mg/L PAA. More importantly, the 24‐h no‐observed‐effect concentration (NOEC) ranged from 1.9 to 5.8 mg/L PAA; the NOEC would be considered as the safe range for culturists to investigate the use of PAA. Decreased alkalinity/hardness increased the toxicity of PAA, while a small increase of dissolved organic content had no effect on PAA toxicity. Results of the present study are important information on the safe application of PAA for the aquaculture industry.     

Spawning induction and seed production of Eastern little tuna,Euthynnus affinis (Cantor, 1849), in the post‐ and pre‐spawning seasons by hormonal treatment in a semi‐closed recirculation system with elevated temperature

We previously established a method for spawning induction in Eastern little tuna (ELT) Euthynnus affinis (Cantor, 1849) by administering a gonadotropin‐releasing hormone analog (GnRHa) during the natural spawning season in Japan (August–October). In order to establish seed production of ELT in the off‐spawning season, we first conducted three spawning induction trials by GnRHa administration from October 2011 to January 2012 using ELT broodstock (2 years old; three females and four males) maintained in a 10‐m³ tank with a semi‐closed recirculation system and static elevated temperature. Average water temperature and daily egg production in three trials lasting 11–15 days were 27.0 ± 0.09°C and 268 173 eggs (Trial 1), 27.0 ± 0.11°C and 277 9098 eggs (Trial 2), and 25.5 ± 0.39°C and 291 113 eggs (Trial 3) respectively. Mean fertilization rate and mean hatching rate were 70.4% and 60.5% (Trial 1), 83.9% and 79.6% (Trial 2), and 62.5% and 57.4% (Trial 3) respectively. We also succeeded in producing ELT larvae in the pre‐spawning season (April–July), although the quantity and quality of larvae produced were inferior to those produced in other calendar months. In trials involving periodic GnRHa administration during the off‐spawning seasons, hatched larvae were obtained in the 10‐m³ tank after six of nine administrations in the 2011–2012 off‐spawning season and in 16 of 19 administrations in the 2012–2013 off‐spawning season. The findings of this study demonstrated that hormonal treatment and thermal control could be used to extend the spawning period in ELT, potentially allowing larval production in the post‐ and pre‐spawning seasons.