C.W Thomas

Growth of juvenile southern rock lobsters, Jasus edwardsii, is influenced by diet and temperature, whilst survival is influenced by diet and tank environment

Abstract The growth and survival of juvenile (2–15 g) southern rock lobsters (Jasus edwardsii) were examined under various culture regimes. In Experiment 1, lobsters held at ambient (13–18°C) or 18°C were fed either fresh mussels, a commercial prawn diet or a moist diet. Growth (specific growth rate (SGR)=1.2–1.32% BW day−1), survival (98%) and food conversion ratios (FCR=1.26–1.29) were significantly better (P 0.05), when the lobsters were fed mussels. There was a significant interaction (P 0.05). The high acceptance and good consumption rate of formulated diets is a positive first step in the development of commercial diets for southern rock lobsters. In Experiment 2, lobsters held at ambient (13–18°C) or 18°C were maintained in tanks containing hides, substrates or neither. Hides increased survival (98%, cf. 60–75%) (P>0.05), although they did not increase growth (P>0.05) compared to tanks without hides. The provision of a substrate to aid the lobsters in the moulting process did not prevent cannibalism. Lobsters grew significantly faster (P

Feed availability and its relationship to survival, growth, dominance and the agonistic behaviour of the southern rock lobster, Jasus edwardsii in captivity.

Abstract The effect of feed availability (ration level and feeding frequency) on the culture performance of the juvenile (5–22 g) southern rock lobster Jasus edwardsii was examined to determine whether multiple daily feeding of a formulated feed would stimulate growth. Furthermore, the relationships between feed availability, agonistic behaviour, dominance, growth and survival were examined. A total of 252 lobsters (mean weight 5.26 g) were stocked into 28 black 52-l tanks at a density of nine lobsters per tank (42 m −2 ) and maintained at a temperature of 18.8 °C in a recirculating seawater system for 119 days. Lobsters were fed with high (4% BW day −1 ) or low (0.5% BW day −1 ) rations divided between one, two or four meals per day. These regimes were compared to a regime of fresh mussels ( Mytilus edulis ) fed to excess once per day. Feeding lobsters with a high-ration level, 4 day −1 , made no significant ( P >0.05) improvements in specific growth rate (SGR) (0.77–0.82% BW day −1 ), survival (75–84%) or biomass yields (96–102 g) compared to feeding 1 or 2 day −1 . Low-ration-fed lobsters had a higher final mean weight (17.5–20.9 g) compared to high-ration lobsters (13.4–14.3 g), however, survival of lobsters that were fed with low ration of 4 day −1 (41%) was significantly ( P P Lobsters were size-ranked (g) to determine the effects of feed competition on the growth and survival of individuals of different rank. The ability and/or motivation of the largest lobsters to maintain their size status increased as feed availability decreased, suggesting that feed restrictions increased the strength of dominance. Size-ranking also demonstrated that small lobsters were more vulnerable to being cannibalised, especially when the feed-ration level was low. Feed competition was consistent with the concept of economic defensibility, predicting that levels of agonistic behaviour are highest when a low ration was patterned into smaller, more easily defended meals (low-ration fed, 4 day −1 ). In contrast, feed competition and agonistic behaviour were rarely observed when feed was freely available (high-ration fed, 4 day −1 ). The high levels of cannibalism of small size-ranked lobsters meant that assessing growth depensation was not a useful approach to the evaluation of the relationships between competition and growth in groups. The implications for J. edwardsii culture are that feeding high-ration levels of formulated feeds, more than once daily, reduces feed competition and incidence of agonistic behaviour. However, there appear to have few benefits in terms of growth or survival. The recommendation from this study is to feed lobsters once daily to excess after dusk.

The effect of temperature on survival, growth, feeding and metabolic activity of the southern rock lobster, Jasus edwardsii.

This study investigated the effect of temperature (18, 20, 22 and 24°C) on growth, feeding and metabolism of post-puerulus lobsters as part of a larger study of the culture potential of farming the southern rock lobster, Jasus edwardsii. There was no significant difference (P>0.05) in the specific growth rates (SGR) at 18, 20 or 22°C; however, growth decreased significantly (P 0.05) in survival at 18, 20 or 22°C. The response of feed conversion ratio (FCR) to temperature was described by a quadratic regression (FCR=0.011T2−0.434T+5.231, r2=0.995), which suggested that the optimum temperature for feed conversion was 19.3°C. Oxygen consumption rates (MO2) increased with increasing temperatures between 18°C and 22°C and declined at 24°C; whilst total ammonia nitrogen (TAN) excretion increased with increasing temperature. The relationships were described by regression equations: MO2=−0.044T2+1.91T−18.553 (r2=1.0); TAN=0.127T−1.174 (r2=0.91). A temperature of 24°C appears to be above the upper thermal tolerance of juvenile J. edwardsii. Lobsters held at this temperature showed reduced survival (compared to those at 18°C), reduced growth (compared to those at 22°C) and appeared to be suffering from respiratory stress (moult-related mortalities, low Q10 between 22°C and 24°C). Overall, the results indicate that juvenile J. edwardsii can be cultured at 22°C without adversely affecting their growth, survival or feed efficiency with optimal temperature range between 19 and 21°C.

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.

Potential use of radiography for measuring feed intake of southern rock lobster (Jasus edwardsii)

The potential of using radiography for measuring feed intake in southern rock lobster Jasus edwardsii (Hutton) was evaluated. Lobsters (14–40 g) readily consumed feeds containing radio-opaque marker (400—450 μm). Marker particles were clearly identified in the stomach 90 min after feeding enabling feed intake to be estimated. Initially low estimates (15±17%; mean±S.D.) of feed intake (expressed as percentage of gravimetric estimates) were recorded due to loss of markers prior to ingestion. Radiographic estimates improved (100±23%; mean±S.D.) when changes to pellet diameter (1.5 mm), moisture content (11%) and binding agent (alginate) were made. Thus, estimates were dependent on pellet diameter and resistance to fragmentation prior to ingestion. To test for the presence of feeding hierarchies in groups of lobsters an experiment was conducted to examine the effect of ration level (high ration: 2.0% BW day−1 and low ration: 0.2% BW day−1) on intra-individual (measured as coefficient of variation for feed intake: CVC) and inter-individual variation (measured as mean share of the group meal: MSM%). There was a significant (P<0.05) negative correlation between CVC and MSM% for the low ration treatments which indicated that small lobsters (CVC=114±19% and MSM%=22±10%: mean±S.D.) were less successful than large lobsters (CVC 44±11% and MSM%=41±13%: mean±S.D.) at obtaining feed. This may be indicative of the formation of feeding hierarchies.

Agonistic behaviour in juvenile southern rock lobster, Jasus edwardsii (Decapoda, Palinuridae): implications for developing aquaculture

Abstract The Southern rock lobster, Jasus edwardsii, is a temperate species of spiny lobster with established well managed fisheries in Australia and New Zealand. It has also been under consideration as a species with aquaculture potential. Agonistic behaviour has important consequences under aquaculture conditions that encompass direct effects, such as damage or death of protagonists, and indirect effects on growth that relate to resource access, principally food and refuge. This study aimed to identify and characterize behaviours and to make a preliminary investigation of their occurrence under tank culture. Juvenile Jasus edwardsii were examined in a flow-through seawater system using a remote video camera system. Twenty-nine behaviours were divided into three sub-groups: aggressive (11), avoidance (6) and others (12). Aggressive behaviours included attacks, pushing, lifting, clasping and carrying an opponent. Avoidance behaviours included moving away in a backwards-, forwards- or side-stepping motion as well as with more vigorous tail flips. These behaviours were components of twelve behavioural groups that described contact, attack and displacement between individuals. Activity was crepuscular with two clear peaks, one in the morning and the other in the evening. The occurrence of behavioural groups was not different between the morning and evening. The frequency of aggressive behaviours was not affected by changes made to stocking density or access to food. The implications of agonistic behaviours are discussed further in relation to developing aquaculture.