Hormonally Induced Spawning, Embryonic Development and Larval Rearing of the Southern Temperate Banded Morwong Cheilodactylus spectabilis

Banded morwong (Cheilodactylus spectabilis) are of interest for marine finfish aquaculture in temperate southern Australia. To improve their ovulatory response, adult females were implanted during the autumn spawning season with slow-release pellets containing 0-400 ug luteinizing hormone releasing hormone analogue (LHRHa)/kg body weight within 24 h of capture from the wild. Compared to the sham control group, animals treated with LHRHa produced significantly more eggs on each day after implantation for the following 7 days (91 +/- 39 ml and 290 +/- 38 ml) and a higher proportion ovulated (8/12 and 27/27). Of fish treated with LHRHa, 93% ovulated two days after implantation and 79% ovulated three times at two-day intervals, whereas control animals showed no cyclicity of ovulation and few ovulated more than once. Egg production was highest at the first ovulation after LHRHa treatment and declined at subsequent ovulations. In a second experiment investigating the range 100-400 ug LHRHa, there was no effect of dose rate on ovulation parameters which additionally examined implantation either immediately after capture or after a 5-day delay. Compared to immediate implantation, a delay resulted in a lower proportion of animals which could be stripped after implantation (100% and 50%, respectively) and the volume of eggs was lower (135 +/- 15 ml and 107 +/- 10 ml). The egg quality was poor following delayed implantation, resulting in no fertilisation after artificial insemination compared with immediate implantation in which fertilisation and hatch rates were higher for eggs collected on Day 2 after implantation (79 +/- 8% and 58 +/- 9%) than on Day 4 (23 +/- 7% and 15 +/- 6%). Thus, it is important to implant animals as soon as possible after capture to ensure optimum egg quality. Good quality eggs were buoyant, spherical and had a diameter of 1050 +/- 25 um with a single pigmented oil droplet of 190 +/- 9 um. When a separate large batch of eggs collected two days after implantation with 100 ug LHRHa was inseminated and cultured at 18 C, larvae hatched after 63 +/- 2 h at a standard length of 2.6 +/- 0.4 mm. Newly-hatched larvae were buoyant and transparent with only a few melanophores, eyes were non-pigmented and jaws were non-funtional. By the fourth day, jaws were functional and eyes were fully pigmented. Utilisation of the endogenous yolk and oil was completed by Day 6 and swimming commenced with exogenous feeding. Larvae, initially fed lipid-enriched rotifers followed by Artemia, reached 8.9 +/- 0.7 mm length on Day 55, after which they metamorphosed to the post-larval paperfish stage of development, 22 +/- 0.9 mm on Day 100, and 43 +/- 1.0 mm at six months old. The results show that treatment of wild-caught females with slow-release pellets containing LHRHa is effective for the production of eggs for hatchery rearing

Temperature effects on the dynamics of gonad and oocyte development in captive wild-caught blacklip (Haliotis rubra) and greenlip (H. laevigata) abalone

Wild-caught blacklip (Haliotis rubra) and greenlip (H. laevigata) abalone were held from spent condition at 12 degrees C, 14 degrees C, 16 degrees C or 18 degrees C and routinely sampled to examine gonad development. Descriptors of gross structure included the Visual Gonad Index (VGI) and the Modified Gonad Bulk Index (MGBI). Oocyte Diameter Ratio (ODR) and oocyte volume (based on an ellipsoid) were used as descriptors of ovarian microstructure. For each species, the rate of increase in the VGI, MGBI and oocyte volume of animals held at different temperatures were used to estimate the Biological Zero Point (BZP), the critical temperature below which no development occurs. BZP estimates derived from the daily increase in VGI and oocyte volume were similar (7.8 degrees C and 7.6 degrees C for blacklip abalone; 6.9 degrees C and 6.8 degrees C for greenlip abalone, respectively), but those based on the increase in MGBI were up to 1.8 degrees C lower (6.0 degrees C and 5.7 degrees C, for blacklip and greenlip abalone, respectively). The mean MGBI, in terms of gonad volume per gram of shucked animal weight, ranged from 5-68 mm3g-1 and 5-58 mm3g-1 for blacklip and greenlip abalone, respectively. The ODR indicated that oocyte shape was highly variable in oocytes < 90 um diameter in both species. Above 90 um, ODR values increased proportionally with oocyte size, indicating a transition in shape from elliptical to round. Ranges for mean oocyte volume for blacklip and greenlip abalone were 0.15-1.4 x 106 um3 and 0.02-1.83 x 106 um3, respectively. The pattern of oocyte growth relative to temperature for both species is illustrated using tables of standardized residuals. Determination of the BZP for blacklip and greenlip abalone enables the calculation of the Effective Accumulative Temperature EAT; the cumulative difference between the water temperature and the BZP, calculated daily) for gamete maturation of these species. This in turn facilitates predictive and deductive estimates of the completion of this process (when water temperature is known) in either natural or artificial (i.e. culture) environments

Sexual maturation in captive spiny lobsters, Jasus edwardsii, and the relationship of fecundity and larval quality with maternal size

Reproductive and somatic parameters of southern rock lobsters, Jasus edwardsii, held captive since puerulus and wild-caught adults were examined in terms of size at onset of maturity (SOM) and fecundity, culminating in an examination of how adult size may relate to larval competency. The SOM was much smaller in captive animals (62.5 mm carapace length, CL) compared to historical fishery data and indicated that precocious maturation may be induced in captivity. During this study, the fecundity was assessed as the number of viable phyllosoma at hatch, which was ~ 45% of egg estimates from the historical fishery data, suggesting either declining egg numbers in wild stocks over time or that major egg loss occurs during embryonic development. The association between SOM and sexual dimorphism was examined for several morphometric parameters. In females, the SOM was concomitant with increases to the width of the 1st and 2nd abdominal segments above 62.5 mm CL, while 2nd and 3rd leg length increased disproportionately in males compared to females above 77.5 mm CL. There were significant correlations between viable fecundity and female size (r = 0.92), phyllosoma size (r = 0.74) and larval viability as quantified by stress indices (r = -0.56) and LD-50 (r = 0.56), indicating that larger females produce larger, more viable larvae. These physiological traits in larval, juvenile and adult animals may have an impact on fishery and aquaculture production

Ozonation of seawater improves the survival of larval southern rock lobster, Jasus edwardsii, in culture from egg to juvenile

Phyllosoma larvae of the southern rock lobster, Jasus edwardsii, were cultured from egg to juvenile. For larvae reared from hatch to Stage III, survival was highest and bacterial contamination was lowest in seawater ozonated at low and moderate levels (400 and 500 mV oxidation-reduction potential, ORP). By contrast, at high ozonation (600 mV), all larvae suffered deformities at the moult to Stage II and terminally starved, while in unozonated water (about 300 mV), all larvae died at Stage III probably as a consequence of Vibrio bacteria profileration. In a second experiment between Stages VI to VIII, larval survival was highest in ozonated water that had been filtered through activated charcoal and coral sand, compared to ozonated water with no filtration or filtered only through activated charcoal. Ozonated water with the combined filtration was used subsequently but there were ongoing deformities, so the level was progressively reduced from 400 mV at Stage VIII to 330 mV at Stage X, at which time ozonation was discontinued. Larvae were then cultured in unozonated water to metamorphosis of eight pueruli at 377 to 437 days after hatch, of which two survived to juvenile. Ozonation was thus effective up to Stage IX in improving culture water to minimise bacterial disease without problems of larval deformities

The effect of predator/prey density and water dynamics on feed intake and growth in spiny lobster larvae (Jasus edwardsii)

Consumption of Artemia by phyllosoma of the spiny lobster Jasus edwardsii was examined under static and turbulent conditions. Phyllosoma larvae were stocked at two densities (2 or 4 phyllosoma container -1; 2P or 4P) and fed juvenile Artemia (1.6mm total length) at two feed rates (1.5 or 0.75 Artemia ml-1; 1.5A or 0.75A) in 50 ml of seawater. This provided a combination of 4 treatments (2P/1.5A, 2P/0.75A, 4P/1.5A, 4P/0.75A). Daily intake of Artemia by phyllosoma was monitored and assessed relative to moult size and intermoult duration at differing predator-prey densities. Phyllosoma numbers were held constant; in the event of mortality, animals were replaced with others from the same cohort cultured under similar conditions. Phyllosoma endogenous reserves at hatch combined with the lowest ration of 0.75 A was sufficient to ensure normal growth and intermoult duration until Stage II. When phyllosoma were fed for an extended period (several moults), low ration and high phyllosoma density resulted in smaller size and extended intermoult duration. Fluctuations in the feeding pattern of phyllosoma were evident between treatments during the experiment. Phyllosoma with access to more Artemia consumed more, and consumption was reduced prior to a moult, even during early stages of development. The second phase of the study examined the intake of 1.7 mm juvenile Artemia by phyllosoma and their response to flow-induced turbulence with a combination of two water exchange rates (2.5 or 5 times h-1) and two inlet positions (2 cm above the water surface or 0.5 cm above the culture vessel bottom and parallel to it). Larvae exposed to slow flow were larger and had a shorter intermoult duration associated with an increased ability to capture and consume more Artemia. Similar numbers of Artemia were consumed during the intermoult in high flow treatments compared to the low flow, albeit over a longer duration. Phyllosoma development between moults required less Artemia to be consumed under static conditions

Feeding Artemia and shellfish to phyllosoma larvae of southern rock lobster (Jasus edwardsii)

Newly-hatched phyllosoma larvae from southern rock lobster (Jasus edwardsii) were grown in culture vessels containing 10 l sea water in a flow-through system at 18 degrees C and fed diets of Artemia sp. and shellfish. The survival and growth of larvae to Stage II was higher when fed ongrown (1.5 mm long) Artemia enriched with Isochrysis galbana (Tahitian strain) at 3 ml-1 compared to those fed pieces (0.5-1 mm) of blue mussel (Mytilus edulis planulatus), clam (Katelesia scalarina) or Pacific oyster (Crassostrea gigas) at 0.08 pieces ml-1. There were no differences in survival, size or intermoult interval for newly-hatched larvae grown to Stage III when fed ongrown Artemia only at densities of 1.5, 3 or 6 ml-1 or for Stage III larvae grown to Stage VI when fed ongrown Artemia at densities of 1.5, 3 or 6 ml-1 plus mussel (0.04 pieces ml-1). Stage VI larvae fed ongrown Artemia plus mussel (0.08 pieces ml-1) were larger by instar 10 than larvae fed mussel only (0.08 or 0.16 pieces ml-1). Lower survival became apparent for the mussel-only treatments 205 days after hatch (at Stages IX or X). The pattern of moulting became progressively less synchronised with each successive stage and instar, so that after instar 11 (about Stage IX), it was difficult to discern discrete peaks in the moulting pattern. The first larva reached Stage XI 288 days after hatch. The size of larvae and duration to successive moults, but not survival, were influenced by parent of origin indicating the importance of selection of broodstock in hatchery rearing

The experimental culture of phyllosoma larvae of southern rock lobster (Jasus edwardsii) in a flow-through system

A system for the experimental larval rearing of phyllosoma of southern rock lobster (Jasus edwardsii) is described. Sea water filtered to 1 um, heated to 18 degrees C and disinfected with ultraviolet light, passes into circular 35 l vessels via a series of jets to achieve constant circular flow. Water exits through a screened drain fitted to the wall of the vessel and positioned to maintain a volume of 10 l with a turnover of 3-4 times per hour. Phyllosoma were cultured in this system from hatch to Stage XI when fed ongrown Artemia and pieces of mussel (Mytilus edulis). The system may readily and cheaply be replicated for experimental comparisons of several treatments

Biochemical composition during growth and starvation of early larval stages of cultured spiny lobster (Jasus edwardsii) phyllosoma

We examined biochemical changes accompanying feeding and starvation from hatch to Stage VI (day 74 after hatch) in spiny lobster, Jasus edwardsii, phyllosoma larvae. Larval dry weights (dw) increased 17-fold from hatch (80 +/- 1 ug) to Stage VI (1415 +/- 44 ug). Larvae starved for 6-11 days at Stages II, IV and VI were 14-40% lighter than their fed counterparts fed enriched Artemia. The increases and losses in total dw during feeding and starvation were associated with changes in the content of protein (constituting 31.4-41.7% of dw) and carbohydrate (constituting 2.6-5.3% of dw), while larger changes in lipid content indicated its greater importance as an energy substrate. Lipid content increased from 7.9% of dw at hatch to its highest of 12.5% at Stage IV, but declined by 50% or more during starvation. This suggests that protein, carbohydrate and lipid are all important energy stores, although lipids are catabolised at a greater rate during food deprivation. The principal lipid class was polar lipid (79-92% of total lipid), followed by sterol (6-20%), with triacylglycerol and other lipid classes at <2%. Polar lipids were catabolized and sterols were conserved during starvation. Changes in the fatty acid profile had mostly occurred before the first moult at day 8 after hatch, with gradual changes thereafter to Stage VI, reflecting their abundance in the Artemia diet. There was some conservation of the major essential fatty acids (EFA), 20:4n-6, 20:5n-3, 22:6n-3, and the fatty acid profile showed large gains in the C18 PUFA, 18:1n-9, 18:2n-6. Ascorbic acid content increased 10-fold from hatch to the end of Stage I (36 and 333 ug g-1 dw, respectively), while the content at the end of Stage II was higher in fed than starved larvae (439 and 174 ug g-1 dw, respectively). Our study will assist in the development of alternatives to nutritionally incomplete diets, such as live ongrown Artemia, to meet the requirements of phyllosoma in culture

Effect of consecutive 9- or 12-month photothermal cycles and handling on sex steroid levels, oocyte development, and reproductive performance in female striped trumpeter Latris lineata (Latrididae)

Duplicate groups of sexually mature striped trumpeter Latris lineata were maintained for two seasons on either a 12-month cycle of ambient temperature (9-18 degrees C) and photoperiod, or a 9-month compressed temperature and photoperiod cycle. One of the duplicates from each cycle was handled frequently (handled) and blood and ovarian samples taken monthly from females until the start of gonadal recrudescence, and then fortnightly until ovulations had ceased. Fish from the other group were not handled (non-handled), except near the end of their spawning seasons to determine which fish had ovulated. Naturally spawned eggs were collected daily from the tanks and hand-stripping was conducted fortnightly in the handled fish during the respective spawning seasons. The 12-month group started spawning in September in both years, whereas the compressed cycle advanced spawning by 1 and 4 months during consecutive seasons, i.e. August 1995 and May 1996. For all handled fish, oocytes developed to late cortical alveoli/early vitellogenic stage, but on average, only 64% of fish continued development through to ovulation. The duration of spawning averaged 45 days for the 9-month and 64 days for the 12-month cycle. The mean volume of eggs produced for each day of production was higher for the handled than the non-handled fish, but there was no difference between cycles (9- and 12-month). Eggs from fish on the 9-month cycle were significantly smaller than from fish on the 12-month cycle. Plasma levels of testosterone (T) and 17beta-oestradiol (E2) in fish from both the 9- and 12-month cycles were at or near their lowest levels at first sampling (<0.3 and 0.5 ng ml -1, respectively) and remained low except for elevations during the 3-4 month period of oocyte maturation and ovulation, when levels peaked at 1.3 and 6.3 ng ml -1, respectively

Tissue content, fecundity and quality of eggs and phyllosoma larvae after supplementing the diet of spiny lobster, Jasus edwardsii, broodstock with ascorbic acid-enriched Artemia biomass

Ascorbic acid (AA)-enriched Artemia in alginate pellets and unenriched pellets were fed to Jasus edwardsii broodstock to supplement AA intake of the basal diet (mussels, squid and compound prawn pellets) during ovarian development before egg extrusion. Pellet AA content ranged from 150 (unenriched) to 9,153 (enriched) g g-1. The basal diet (150 g AA g-1) was compared to low (150), medium (450) and high (1,350 AA g g-1) AA supplementation. Dietary AA content was obtained using combinations of unenriched and AA-enriched Artemia in combination with the basal diet. Supplementation resulted in ovarian AA saturation at ~240 g g-1, increasing ovarian content by 160%. Digestive gland concentrations were 76-92 g AA g-1 for diets containing 450 g AA g-1, but reached 270 g AA g-1 for the high supplement. The considerable AA store in tail muscle appeared to be translocated to the ovary during maturation. There was no significant AA depletion in eggs during embryogenesis suggesting minimal AA utilization during this phase. J. edwardsii spawns once annually, unlike other multiple spawning crustaceans. Therefore, AA supplementation did not alter fecundity or phyllosoma quality but resulted in a dose-dependent increase (up to 33%) in AA content of eggs and phyllosoma