Natural Spawning Research Articles

The genetic approach for assessing sea trout stock enhancement efficiency – An example from the Vistula River

Abstract Many countries in the Baltic Sea basin have initiated enhancement programs for Baltic migratory sea trout, Salmo trutta L., to compensate for losses stemming from anthropogenic pressure that has resulted in the declining population abundance of this species. Regular stock enhancement has been conducted in Poland since the 1960s. Currently, over one million sea trout smolts are released into Polish rivers annually. In most Baltic countries, including Poland, stock enhancement depends on hatcheries producing material using spawners caught in native rivers. However, increasing difficulty obtaining spawners in recent years in Poland has meant that stock enhancement performed in the Vistula has been done largely with material obtained from broodstocks. Simultaneously, there is a lack of information regarding the proportion of wild and cultured sea trout in this river basin. This paper is a review of methods applied to identify individuals from natural and artificial sea trout spawning in rivers, and it proposes using genetic techniques as an alternative to traditional marking methods. A set of 13 microsatellite loci are proposed that are characterized by high selectivity. Using negative controls while simulating the assignment of parental pairs revealed that the number of loci in the set was highly significant and should not be reduced. This method could be useful in the proposed assessment of the proportions of wild and cultured fish in Polish rivers.

Constant Temperature Artificial Incubation of Spawned Eggs in Natural Nests from the Chinese Freshwater Soft-Shelled Turtle, Tryonyx sinensis Strauch(1862).

ABSTRACTOn June 14, 2008 (the first experiment) and July 24, 2008 (the second experiment), the shores of the Boseong River and the sandy beaches, Seokgok-myun, Moksadong-myun, Gokseong-gun in Jeollanam Province were investigated and a total of 29 soft-shelled turtle (Tryonyx sinensis) eggs in the natural spawning nest eggs were collected (13 eggs were collected in the first experiment and 16 eggs in the second experiment). The temperatures in the natural spawning nests were 25.9-36.9±0.5℃, the depth of the eggs was 5.2-7.5±0.5 cm as the distance of the average 6.4±0.5 cm. 29 eggs were scattered at least 0.2 cm interval. Artificial incubation of 29 eggs was conducted in artificial nest boxes in thermo-plastic composition of the incubator, and then incubated at 26.5-35.5±0.5℃, and an average constant temperature was 31.2-32.1±1.0℃. The incubation days ranged from 53 to 55. In case of most turtles, incubation at 31℃ (higher temperatures) generally produces all or mostly females, while incubation at 25℃(cooler temperatures) produces all or mostly males. Exceptionally, in case of genus Trionyx, the sex ratio of female : male of T. sinensis of a freshwater soft-shelled turtle was approximately 1:1, which differs from other genera of turtles and makes T. sinensis Strauch only turtles presently known to lack temperature-dependent sex determination.

Snakehead Fish (Channa Striata) : Semi-Induced Breeding and Larval Growth

Objectives:The purposes of the present study are to produce technology of the snakehead fish breeding in Central Kalimantan region of Indonesia and to analyze the growth of larvae produced. Methods/Statistical Analysis:The experiments are conducted using twenty four of the broodstock and a pairof the fish isplaced to the hapa.The ovaprim doses injected on dorsal of the fish in this experiment are A: 0 ml/kg (control), B: 0.3 ml/kg, C: 0.5 ml/kg and D: 0.7 ml/ kg body weight of fish. The parameters are observed that the natural spawning of the fish and total larval body length of larvae. Findings:Spawning is observed 30-37 hours after application of ovaprim with dose 0.5 ml/kg, followed by application of 0.3 ml /kg ovaprim dose with spawning latency time of 4-5 days.During the early stages total length growth is increasedgradually and sharply. It is increased further and after 20 daysfrom hatching until the end of experiment as well as digestive tract development. Improvement/Applications: At day 25 after hatching coinciding to presence of pyloric caeca the fish may be introduced artificial feeds.

Bringing back the giants: juvenile Tridacna gigas from natural spawning of restocked giant clams

Bringing back the giants: juvenile Tridacna gigas from natural spawning of restocked giant clams

ПРОХОДНЫЕ ОСЕТРОВЫЕ (ACIPENSERIDAE, ACTINOPTERYGII) р. ДОН ВЫШЕ ЦИМЛЯНСКОГО ГИДРОУЗЛА

Based on the literature, non-published and survey data, information on the occurrence of anadromous sturgeons after the regulation of the Don River downstream and upstream of the Tsimlyansk Dam is given. There were two peaks of mature adults approaching the dam, namely, in the 1950s and 1980s. The first mass peak was associated with the wild population existed then; the second one was a result of mass artificial breeding. At the first stage, the sturgeon (Acipenser gueldenstaedtii Brandt et Ratzeburg, 1833) and beluga (Huso huso (Linnaeus, 1758)) prevailed below the dam; at the second one, just the sturgeon did. Since 1955, only 21 individuals of anadromous sturgeons were transported through the dam by a fish ladder. During 1952-1961, 1,145 individuals were transported into the reservoir, including 218 belugas. Separate beluga individuals were transported later on as well. There is evidence of the presence of young beluga individuals from natural spawning in the reservoir before the 1970s. The latest known adult sturgeon and stellate sturgeon (Acipenser stellatus Pallas, 1771) in the reservoir were noted in the 1980-90s. Separate beluga individuals have been met until now. The youngest of the noted individuals belong roughly to the generations of the early 1990s. It is concluded on the existence of an extremely low-abundant landlocked form of the Azov beluga in the reservoir.

The effectiveness of hanging culture bloody clams, Scapharca kagoshimensis, as a parental stock for natural spawning induction and the potential for artificial regulation of spawning in Lake Nakaumi, Japan

The effectiveness of hanging culture bloody clams, <I>Scapharca kagoshimensis</I>, as a parental stock for natural spawning induction and the potential for artificial regulation of spawning in Lake Nakaumi, Japan

Channel catfish Ictalurus punctatus strain comparison for induced ovulation in the early spawning season to produce channel catfish ♀ × blue catfish I. furcatus ♂ hybrid catfish embryos

The channel catfish (Ictalurus punctatus) ♀×blue catfish (Ictalurus furcatus) ♂ hybrid catfish has superior performance in respect to survival, growth rate, feed conversion, low dissolved oxygen, and fillet yields compared to its parent species. Currently the demand for hybrid fingerlings is greater than available supply. Selective breeding for early spawning could extend the spawning season to partially address this problem. Under commercial conditions and using natural open pond spawning, the Thompson line of channel catfish spawns earlier at its location than other strains at their home farms. Over a 4-year period the Thompson line was compared to the Kansas strain and AR line for fry production in the early spawning season using induced spawning with luteinizing hormone-releasing hormone analogue implants to induce ovulation, followed by hand stripping, and in vitro fertilization techniques. Relative reproductive performance was variable among years, but in general, fry output of the three strains was similar and relatively high, with the 3-year average of both Thompson and Kansas strains being approximately 2500fry/kg. The observed fry output of Thompson was about 15% higher than that for Kansas, which was not significantly different because of the high variation among years. The early spawning of the Thompson line appears to be due to an environmental effect, related to genotype-environment interactions or natural spawning and response to induced spawning are actually two different traits. Strains of more northerly origin might be evaluated to achieve the goal of better response to early induced spawning.

Broodstock History Strongly Influences Natural Spawning Success in Hatchery Steelhead (Oncorhynchus mykiss).

We used genetic parentage analysis of 6200 potential parents and 5497 juvenile offspring to evaluate the relative reproductive success of hatchery and natural steelhead (Onchorhynchus mykiss) when spawning in the wild between 2008 and 2011 in the Wenatchee River, Washington. Hatchery fish originating from two prior generation hatchery parents had <20% of the reproductive success of natural origin spawners. In contrast, hatchery females originating from a cross between two natural origin parents of the prior generation had equivalent or better reproductive success than natural origin females. Males originating from such a cross had reproductive success of 26–93% that of natural males. The reproductive success of hatchery females and males from crosses consisting of one natural origin fish and one hatchery origin fish was 24–54% that of natural fish. The strong influence of hatchery broodstock origin on reproductive success confirms similar results from a previous study of a different population of the same species and suggests a genetic basis for the low reproductive success of hatchery steelhead, although environmental factors cannot be entirely ruled out. In addition to broodstock origin, fish size, return time, age, and spawning location were significant predictors of reproductive success. Our results indicate that incorporating natural fish into hatchery broodstock is clearly beneficial for improving subsequent natural spawning success, even in a population that has a decades-long history of hatchery releases, as is the case in the Wenatchee River.

Reproduction of cod, Gadus morhua (Actinopterygii: Gadiformes: Gadidae), from the Gdańsk Deep (Baltic Sea) under controlled conditions

Background. The stocks of cod, Gadus morhua Linnaeus, 1758, have been declining within recent decades and the Baltic Sea is one of the most affected areas. The latter body of water with its low salinity, pollution, and vast areas of demersal hypoxia is particularly vulnerable. Areas of natural spawning are scarce and the reproductive output of cod has been irregular and more and more limited. One of the proposed solutions for this problem might be an artificial reproduction.  One of such areas has been the Gdańsk Deep, but the number of potential brood fish is relatively low, which makes the eggs and sperm poorly accessible. The aim of the presently reported study was to conduct spawning and egg incubation under controlled conditions to obtain viable hatchlings and to monitor the embryonic development of cod originating from the area of the Gdańsk Deep. Materials and methods. The parental fish specimens were obtained during commercial trawl catches. The eggs were fertilized artificially at the field laboratory using filtered brackish sea water with salinity of 15‰, and then were incubated at a constant temperature of 8 ± 0.5°C. Eggs and larvae development, and larvae beginning exogenous feeding were observed under a stereo microscope, and photographed regularly to determine the sizes of the eggs and larvae and to document the results of the experiment. Results. The mean percentage of fertilization of eggs was 70%. Hatching began 236 h after fertilization, and the newly hatched larvae comprised 30% of the initial stocking density. The mean length of the larvae was 3.95 mm. The cod larvae began exogenous feeding before the yolk sac was fully absorbed. Conclusion. Artificial reproduction with gametes obtained from cod spawning in the Gdańsk Deep is possible, and the fertilization rates obtained were similar to those achieved with cod from the Bornholm and Gotland basins. Therefore, our results also show that cod spawning in the Gdańsk Deep can be suggested as a model species for further research.

Natural and artificial spawning strategies with fresh and cryopreserved semen in Rhamdia quelen: Reproductive parameters and genetic variability of offspring

This study evaluated the reproductive parameters and genetic variability of offspring of Rhamdia quelen from mating by natural spawning and by controlled fertilization with fresh and cryopreserved semen. After hormonal manipulation, three R quelen pairs were used for natural spawning in high-flow tanks, three pairs were used for mating with fresh semen, and another three pairs were used with cryopreserved semen. Matings were performed in triplicate. For matings with fresh and cryopreserved semen, semen from each male was used to individually fertilize oocytes from each female. Pools of semen and oocytes were made, and aliquots of these gametes were taken for fertilization. No differences (P > 0.05) were detected for absolute or relative fecundity, fertilization rate, or egg hatching rate. The use of fresh semen led to a higher (P < 0.01) percentage of normal larvae. The use of fresh semen in pooled mating resulted in a greater effective number of alleles and a higher expected heterozygosity. Offspring from natural spawning presented higher observed heterozygosity and a lower inbreeding coefficient. The highest inbreeding coefficient was found in offspring from individual matings using fresh semen. Regarding paternal contributions, a single male dominated in matings with fresh semen, whereas two males dominated in natural spawning and matings using cryopreserved semen. The use of gamete pools for mating and natural spawning resulted in higher genetic variability of offspring, and mating using cryopreserved semen found no effects on genetic variability of offspring but did reduce the percentage of normal larvae. Other reproductive parameters were not influenced by spawning strategies.

White Crappie Tank Culture and Out‐of‐Season Spawning

AbstractWhile extensive crappie culture has been practiced for decades, limited knowledge of crappie aquaculture methods has hampered the production potential of White Crappie Pomoxis annularis to a small time frame during the natural spawning season, which occurs only once annually. Out‐of‐season spawning of White Crappie could greatly enhance annual production potential. Therefore, White Crappie out‐of‐season spawning experiments were conducted from November to February in recirculating tank systems. After 2 weeks of simulated winter (10°C, 8 h light), photoperiod and temperature were increased to spring (22°C, 16 h light) conditions over 3 weeks (1°C and 30 min increase every 2 d) and 6 weeks (1°C and 30 min increase every 4 d). Fish were injected with gonadotropin‐releasing hormone analog (GnRHa; 100% priming dose and 100% resolving dose, 24 and 48 h later) and strip‐spawned upon ovulation. The 3‐week treatment (11 females : 10 males) induced 1 female to spawn with 11% fertilization rate. The 6‐week treatment (12 females : 10 males) induced 2 females to spawn with fertilization rates of 31.5% and 79.2%. Gonads of unspawned females were sampled at 96 h after the resolving dose to assess reproductive maturity. Gonadosomatic index (GSI) and egg diameter (ED) from unspawned females (3‐week GSI [mean ± SE] = 0.02 ± 0.01, ED = 0.71 ± 0.22; 6‐week GSI = 0.03 ± 0.02, ED = 0.72 ± 0.10) were compared with wild females sampled during December (winter; GSI = 0.02 ± 0.01; ED = 0.53 ± 0.07) and April (spring; GSI = 0.04 ± 0.01; ED = 0.90 ± 0.12). No difference between 6‐week GSI and spring GSI was detected; however, ED was smaller for 3‐ and 6‐week treatments when compared with spring ED. Therefore, out‐of‐season spawning of White Crappies, using recirculating tank systems and hormone‐induced spawning, is possible, but a longer seasonal shift regime is needed to enhance spawning success.

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

AbstractLocalized 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.

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.

Review: A River Between Us

A River Between Us (DVD, 90 minutes; Green Planet Films, 2015; http://www.greenplanetfilms.org) The struggle in the West over water has been long and bitter, pitting family farmers against Native Americans, fishers, and environmentalists. No case has brought more attention to these multiuser conflicts than the fight over habitat restoration for the five species of Pacific salmon – most notably the favored commercial and sport fishing species, Chinook (or king) and coho salmon. Over the past hundred years, salmon populations have declined precipitously on the Pacific coast, and many stocks of Chinook and coho are now threatened or endangered due to declines in habitat quality and dams that block upstream passage of adults to their natal spawning grounds. A River Between Us highlights these conflicts in one of the formerly most productive and most politically sensitive river basins, the Klamath in California and Oregon. Historical records indicate that the Klamath River supported immense runs of salmon, including both Chinook and coho that sometimes numbered …

Culture, reproduction and embryogenesis of wild zebrafish (Danio rerio) in laboratory condition

Zebrafish (Danio rerio: Hamilton, 1822) is a well-known model organism of biological research. Generally it is found in the fresh water ponds. However, the culture, breeding and embryonic development of wild D. rerio of Bangladesh is scarcely represented in the literature. Therefore, a laboratory experiment was conducted to study these aspects of local zebrafish. Water quality parameters for adult fish husbandry system were recorded. These were temperature (°C) 29.18 ± 1.53, pH 7.55 ± 0.144, TDS (ppm) 225 ± 11.136, (ORP) 48.93 ± 26.04, DO (ppm) 1.24 ± 0.591, conductivity (mS/cm) 0.450 ± 0.022, are resistivity (Mῼcm) 0.0026 ± 0.00049 for adult fish tanks. The parameters obtained from larvae rearing ranks were temperature (°C) 29.56 ± 0.777, pH 7.73 ± 0.421, TDS (ppm) 198.33 ± 39.627, (ORP) 51.37 ± 17.387, DO (ppm) 2.02 ± 0.694, conductivity (mS/cm) 0.397 ± 0.079, resistivity (MΩcm) 0.0026 ± 0.00044. After one month of rearing, adult male and female fishes were selected for natural breeding and spawning and obtained 87.5 ± 7.72% spawning success, 96.83±0.81% fertilization rate and 94.89 ± 0.27% hatching rate. The embryonic development for zygote, cleavage, blastula, gastrula, segmentation and pharyngula periods were observed and obtained proper development for each state at 28.5ºC. The survival rate of hatchlings was 10 - 20% up to 20 days post fertilization. The higher spawning success, fertilization rate, hatching rate and survival rate indicate the possibility and potentiality of culturing zebrafish in laboratory conditions and could be established as a model animal for Bangladeshi researchers.&#x0D; Dhaka Univ. J. Biol. Sci. 25(2): 139-148, 2016 (July)

Enhancement of oogenesis/spermatogenesis in meagre Argyrosomus regius using a combination of temperature control and GnRHa treatments

A multiple GnRHa injection method for inducing spawning of high fecundity and quality in meagre was optimized. Specifically, the study (a) examined how long females would continue spawning in response to consecutive, weekly GnRHa injections, if maintained at the natural spawning temperature, and (b) evaluated whether males can produce adequate amounts of good quality sperm for the same period, with the assistance of a GnRHa therapy. Combined with stable temperatures (19–20°C) that are prevalent during the early spawning season (April–May) in the Mediterranean Sea, each weekly GnRHa injection induced ~2 consecutive spawns per week for a period of 17weeks. Fish spawned consistently 2days after treatment and produced high fecundity and egg quality (i.e. fertilization, hatching and early larval development). Maximum mean total fecundity (±S.D.) obtained was 1,415,000±149,000eggskg−1 in 32 spawns, being the highest total season fecundity reported for meagre, and significantly higher than the estimated maximum potential fecundity for the species. At the same time, sperm of consistently high quality (i.e. initial motility, duration of motility and storage survival) was produced in response to treatment with multiple GnRHa implants, though towards the end of the experiment a significant reduction (ANOVA, P≤0.05) in spermatozoa density was observed. This protocol is expected to enhance greatly commercial production of meagre. Statement of relevanceThe present study reports on an optimized protocol for the induction of consistent and repeated spawning in meagre, based on the use of weekly GnRHa injections combined with stable temperatures that are prevalent at the early spawning season in the Mediterranean Sea. This protocol produced eggs of high fecundity and quality (i.e. fertilization, hatching and early larval development) for a period of >4months, and it is expected to enhance greatly commercial production of meagre.

Variability in larval period, post-setting growth and survival of the oyster Crassostrea belcheri produced by gamete stripping method

Gamete stripping is the most practical method in oyster production because the time of fertilization can be precisely controlled. However, it was found that there was much greater variability in the speed of egg development compared with natural spawning. In this study, three groups of larvae (aged 21, 27 and 29 d) were successively separated from fertilization to the pediveliger stage among all the larvae produced by the stripping method. No differences in the spat growth rate were found among the larval periods at 15 d of the experiment (p ≥ 0.05), but spat growth and survival rates of juvenile oysters in the larval periods of 21 and 27 d were significantly higher than those for 29 d at the end of the experiment (30 d). The positive correlation between larval growth rates and the spat daily yield at 30 d was significant. These results indicated that the gamete stripping method produced high variations in the larval period and post-setting growth and survival in the oyster, Crassostrea belcheri.

Five-year evaluation of habitat remediation in Thunder Bay, Lake Huron: Comparison of constructed reef characteristics that attract spawning lake trout

Degradation of aquatic habitats has motivated construction and research on the use of artificial reefs to enhance production of fish populations. However, reefs are often poorly planned, reef design characteristics are not evaluated, and reef assessments are short-term. We constructed 29 reefs in Thunder Bay, Lake Huron, in 2010 and 2011 to mitigate for degradation of a putative lake trout spawning reef. Reefs were designed to evaluate lake trout preferences for height, orientation, and size, and were compared with two degraded natural reefs and a high-quality natural reef (East Reef). Eggs and fry were sampled on each reef for five years post-construction, and movements of 40 tagged lake trout were tracked during three spawning seasons using acoustic telemetry. Numbers of adults and spawning on the constructed reefs were initially low, but increased significantly over the five years, while remaining consistent on East Reef. Adult density, egg deposition, and fry catch were not related to reef height or orientation of the constructed reefs, but were related to reef size and adjacency to East Reef. Adult lake trout visited and spawned on all except the smallest constructed reefs. Of the metrics used to evaluate the reefs, acoustic telemetry produced the most valuable and consistent data, including fine-scale examination of lake trout movements relative to individual reefs. Telemetry data, supplemented with diver observations, identified several previously unknown natural spawning sites, including the high-use portions of East Reef. Reef construction has increased the capacity for fry production in Thunder Bay without apparently decreasing the use of the natural reef. Results of this project emphasize the importance of multi-year reef assessment, use of multiple assessment methods, and comparison of reef characteristics when developing artificial reef projects. Specific guidelines for construction of reefs focused on enhancing lake trout spawning are suggested.

Morphological Development of Embryo, Larvae and Juvenile in Yellowtail Kingfish, Seriola lalandi.

This study monitored the morphological development of embryo, larvae and juvenile yellowtail kingfish, Seriola lalandi, for their aquaculture. The fertilized eggs obtained by natural spawning were spherical shape and buoyant. Fertilized eggs were transparent and had one oil globule in the yolk, with an egg diameter of 1.35 ± 0.04 mm and an oil globule diameter of 0.32 ± 0.02 mm. The fertilized eggs hatched 67–75 h after fertilization in water at 20 ± 0.5°C. The total length (TL) of the hatched larvae was 3.62 ± 0.16 mm. During hatching, the larvae, with their mouth and anus not yet opened. The yolk was completely absorbed 3 days after hatching (DAH), while the TL of post-larvae was 4.72 ± 0.07 mm. At 40 DAH, the juveniles had grown to 30.44 ± 4.07 mm in TL, body depth increased, the body color changed to a black, yellow, and light gray-blue color, and 3–4 vertical stripes appeared. At 45 DAH, the juveniles were 38.67 ± 5.65 mm in TL and 10.10 ± 0.94 mm in body depth. The fish were green with a light orange color, with 7 faint green-brown stripes on the sides of their body. At 87 DAH, the juveniles had grown to 236.11 mm in TL, 217.68 mm in fork length, and 136.5 g in weight. The fish resembled their adult form, with a light yellow-green body color, loss of the pattern on the sides of their body, and a yellow coloration at the tip of the caudal fin.

Management of Sexual Maturation and Natural Spawning of Captive- Reared Yellowtail Kingfish, Seriola lalandi, in an Indoor Rearing Tank.

This study describes results on sexual maturation and characteristics of natural spawned eggs to develop a method for the production of stable, healthy fertilized eggs from captive-reared yellowtail kingfish, Seriola lalandi. A total of 59 yellowtail kingfish were captured off the coast of Jeju Island, after which the broodstock was cultured in indoor culture tank (100 m3) until they were 6.1–14.9 kg in body weight. As part of the rearing management for induced sex maturation, the intensity of illumination was maintained at 130 lux. The photoperiod (light/dark; L/D) was set to a 12 L/12 D from October 2013 to January 2014, and 15 L/9 D from February 2014 to June 2014. Feeds comprised mainly EP (Extruded Pellets), with squid cuttlefish added for improvement of egg quality, and was given from April to June 2014. The first spawning of yellowtail kingfish occurred in May 3, 2014, at a water temperature of 17.0°C. Spawning continued until June 12, 2014, with the water temperature set at 20.5°C. Time of spawning was 26 times at this period. The total number of eggs that spawned during the spawning period was 4,449×103. The buoyant rate of spawning eggs and fertilization rate of buoyant eggs during the spawned period were 76.1% and 100%, respectively. The diameters of the egg and oil globule were 1.388 ± 0.041 mm and 0.378 ± 0.029 mm, respectively, which was higher in early eggs than in those from late during the spawned period.