Grow‐out culture of abalone Haliotis tuberculata coccinea Reeve,fed land‐based IMTA produced macroalgae,in a combined fish/abalone offshore mariculture system: effect of stocking density

Haliotis tuberculata coccinea has been identified as a target species for European aquaculture development, in order to fulfil the rising demand for abalone. The effects of different stocking densities on the growth performance, feed utilization and survival of two different initial size groups (30 and 40 mm) of abalones, during the final grow‐out to cocktail/market size (45–60 mm), were determined over a 6‐month period. Trials were performed in abalone cages installed in a commercial open‐sea cages fish farm. Animals were fed the red algae Gracilaria cornea and the green one Ulva rigida, both obtained from a land‐based integrated multi‐trophic aquaculture system. Survival rates were very high (94–98%) regardless the density employed. Sustained high linear growth was recorded both in shell and weight. However, a 17–19% reduction in weight gain was obtained by doubling the initial stocking density, suggesting a higher competition for space or food. Nevertheless, the high growth performance (70–94   μm day^?1; 250–372% weight gain) and survival attained, even at high densities, denoted the suitability of the offshore mariculture system as well as the biofilter produced macroalgae for grow‐out culture of H. tuberculata coccinea that overall could reach cocktail/commercial size in only 18–22 months.     

Production and sinking rates for bio‐deposits of abalone (Haliotis discus hannai Ino)

Particle size distribution, organic content and the sinking velocity of bio‐deposits of abalone Haliotis discus hannai Ino were evaluated. The abalone was divided into three size classes according to shell length: Group B: 68.8 ± 2.8 mm, group M: 56.1 ± 2.3 mm and group S: 42.4 ± 2.8 mm. The faecal pellets had an amorphous shape, with a cross‐sectional area ranging from 0.01 to 2.64 mm². The mean cross‐sectional area varied among the size classes: 0.59 (B), 0.21 (M) and 0.12 (S) mm². The bio‐deposit organic content was similar among the groups (B: 18.3 ± 1.1%; M: 19.9 ± 0.9%; S: 19.3 ± 1.0%). Sinking velocity ranged from 0.5 to 2.3 cm s^?1. Larger abalone tended to have larger and thus faster‐sinking faecal pellets. The median sinking velocity for groups B, M and S was 0.9, 0.5 and 0.7 cm s^?1 respectively. The mean daily production rates for groups S, M and B were 2.8 ± 1.2, 3.4 ± 1.3 and 4.3 ± 1.8 g ind.^?1 respectively. Bio‐deposit production rate estimated to be between 134.4 and 206.4 mg m^?2 day^?1 in the bay. Our results suggest that the pellet size was within the appropriate size range for filter‐feeding bivalves.     

Nutritional value of Pavlova spp. (Prymnesiophyceae) for spat of the Cortez oyster Crassostrea corteziensis during late-nursery culturing at the hatchery

Three Pavlova species were evaluated for their nutritional value as diets for growth and survival of the Cortez oyster Crassostrea corteziensis spat during late‐nursery cultivation at a hatchery. Microalgae were provided as monospecific diets (Pavlova salina, P. sp. C50 and P. sp. C53) and in binary combinations of diets 1+2, 1+3 and 2+3 at 80–90 × 10³ cells mL^?1 for 21 days. Juveniles experienced high survival rates and grew well with all dietary treatments, but binary diets yielded greater survival and growth of spat. From the three binary treatments, Diet 6 (P. sp. C50 and P. sp. C53) promoted significantly (P<0.001) fastest growth of juveniles in shell height (0.19 mm day^?1), shell length (0.14 mm day^?1), total wet weight (0.04 g day^?1) and dry weight of meat biomass (0.024 g day^?1). For all shell dimensions, the lowest growth rates occurred with Diets 2 (P. sp. C56 alone) and 3 (P. sp. C50 alone). These results highlight the importance of testing microalgal diets for bivalve spat rather than just relying on published nutritional values.     

Use of thraustochytrid <Emphasis Type="Italic">Schizochytrium</Emphasis> sp. as source of lipid and fatty acid in a formulated diet for abalone <Emphasis Type="Italic">Haliotis asinina</Emphasis> (Linnaeus) juveniles

The effects of using thraustochytrid Schizochytrium sp. as source of lipid and fatty acids in a formulated diet on growth, survival, body composition, and salinity tolerance of juvenile donkey’s ear abalone, Haliotis asinina, were investigated. Treatments consisted of diets either containing a 1:1 ratio of cod liver oil (CLO) and soybean oil (SBO) (Diet 1) or thraustochytrid (Diet 2) as source of lipid and fatty acids at 2 % level. Natural diet Gracilariopsis heteroclada (Diet 3) served as the control. No significant difference in growth was observed in abalone fed Diet 3 (SGR: 5.3 % BW day^?1; DISL: 265 μm day^?1) and Diet 2 (SGR: 5.2 % BW day^?1; DISL: 255 μm day^?1). Survival ranged from 78 to 85 % for all treatments and was not significantly different from each other. A 96-h salinity stress test showed highest survival of 84 % in abalone fed Diet 2 compared with those fed diets 1 and 3 (42 %). The high growth rate of abalone fed Diet 2 and high tolerance to low salinity could be attributed to its high DHA content (8.9 %), which resulted to its high DHA/EPA ratio of 10.5 %. These fatty acids play a significant role in abalone nutrition. The fatty acid profile of abalone meat is a reflective of the fatty acid profile of the oil sources in the diet. The present study suggests that the use of Schizochytrium oil in lieu of CLO and SBO can support good growth of abalone which is comparable with abalone fed the natural seaweeds diet.     

Effects of alternate starvation and refeeding cycles on food consumption and compensatory growth of abalone, Haliotis asinina (Linnaeus)

The effects of alternate starvation and refeeding on food consumption and compensatory growth of hatchery‐bred abalone, Haliotis asinina (Linnaeus), were determined. Two groups of abalone juveniles (mean shell length = 29 mm, body weight = 5 g) were alternately starved and refed a macro‐alga, Gracilariopsis bailinae at equal duration (5/5 or 10/10) over 140 days. A control group (FR) was fed the seaweed ad libitum throughout a 200‐day experimental period. Starved and refed abalone showed slower growth rates (DGR, 63 and 70 mg/day in the 5/5 and 10/10 groups respectively), as a result of reduced food intake (DFI 15% and 16% day^?1 respectively), after repeated starvation and refeeding cycles. Percentage weight gains (5/5 = 196%, 10/10 = 177%) were significantly lower than that of the control (397%). When refed continuously over 60 days, the starved groups exhibited increased DFI and fed at the rate of 24% and 25% day^?1, which were not significantly different from that of the control at 26% day^?1. At the end of the experiment, no significant differences were observed among three treatments in terms of shell length (range: 46–48 mm), body weight (range 25–28 g), % weight gain (392–465%) and per cent survival (range 87–98%). The results indicated that H. asinina had a complete compensatory growth following a return to full rations after a series of intermittent starvation and refeeding cycles.     

A Growth Assessment of Juvenile Abalone Haliotis laevigata Fed Enriched Macroalgae Ulva rigida

The experiment was conducted to assess the growth of juvenile greenlip abalone Haliotis laevigata fed a range of Ulva rigida diets with different nitrogen contents and an artificial pelleted diet. The minimal nutrient concentration resulting in significant enrichment of U. rigida was 2.25 mg N l^?1. The maximum nitrogen content obtained by U. rigida in this study was 6.099%, which resulted from an inorganic nutrient concentration of 7 mg N l^?1. However, no further significant increase in enrichment occurred from nutrient concentrations of 10 and 15 mg N l^?1. Abalone specific growth rate in shell length (SGR_L) and wet weight (SGR_W) and foot muscle yield were significantly higher for abalone fed the artificial diet compared to those fed any U. rigida diet. Abalone fed U. rigida enriched in less than 15 mg N l^?1 had similar growth rates compared to abalone fed unenriched U. rigida. Abalone fed the artificial diet contributed a higher percentage of weight gain into the valuable foot muscle. The foot muscle moisture content of abalone fed the artificial diet was significantly lower than that of abalone fed any U. rigida diet. The conclusions reached by this study should assist Australian abalone producers in assessing the potential benefits of using U. rigida as an effluent biofilter and subsequent food source for the commercially important juvenile greenlip abalone.     

Growth of the abalone Haliotis diversicolor (Reeve) fed with macroalgae in floating net cage and plastic tank

The abalone Haliotis diversicolor (Reeve) or ‘tokobushi’ is being cultured in Kagoshima, southern Japan for stock enhancement of fishing grounds. However, with decreasing catches from the wild some fishermen's group may eventually resort to rearing tokobushi until of marketable size. Growth experiments of tokobushi fed macroalgae in floating net cage and plastic tanks were conducted to evaluate the influence of culture system, macroalgal food, age and water temperature on their culture. In floating net cage, marketable sizes were obtained at the age of 457–822‐day old (15–27‐month old) with highest growth rate of 2.36% g day^?1 and 0.21 mm day^?1. One advantage of the plastic tank culture system was that the tokobushi shell remained clean throughout the culture period. Macroalgal food affected the growth rate; Sargassum fusiforme (Setchell)‐ and Ulva pertusa (Kjellman)‐fed tokobushi were better than Meristotheca papulosa (Montagne)‐fed. Further, 1‐year‐old tokobushi had better growth performance and condition index than the 2‐year‐old cohort, and growth rates were higher at 17°C than at 12°C. These findings should help tokobushi farmers design their mariculture scheme considering both economic and environmental aspects.     

Effects of temperature and salinity on survival and growth of juvenile ark shell <Emphasis Type="Italic">Anadara broughtonii</Emphasis>

We investigated the combined effects of temperature (23, 26, 29 and 32 °C) and salinity [15, 18, 21, 24, 27 and 30 practical salinity units (PSU)] on the growth and survival of juvenile ark shell Anadara broughtonii under hatchery conditions. Mortality, shell length and shell height were monitored for a period of 25 days in all exposure groups. Survival greater than 98% was observed in all treatment groups with no significant difference among treatment combinations. Absolute growth and specific shell length and height growth rate were significantly influenced by temperature and salinity. Growth of juvenile A. broughtonii increased with higher salinity and peaked at an intermediate temperature (26 °C). Optimal specific growth rates of 4.64 ± 0.04% day^?1 by shell length and 4.76 ± 0.11% day^?1 by shell height were observed at a combination of 26 °C and 30 PSU. This study enhances our understanding of the biology of A. broughtonii and determines ideal environmental conditions for pre-planting culture operations.     

The protein and energy requirements of farmed South African abalone Haliotis midae L. cultured at optimal and elevated water temperatures

Formulated abalone feeds used by the culture industry are believed to be unsuitable for use at elevated water temperatures (>20 °C). The aim of this study was to develop a feed that could safely be fed to abalone cultured at elevated water temperatures by optimizing dietary protein/energy levels. Abalone (54.90 ± 0.08 mm; 28.99 ± 0.16 g) were cultured at either 18, 22 or 24 °C, and fed diets containing graded levels of protein (18–26%) and energy (11.6–16.2 MJ kg^?1). Abalone growth was temperature dependent, declining from 4.33 g month^?1 at 18 °C to 0.77 g month^?1 at 24 °C. Shell length and weight gain were independent of dietary protein, provided that the digestible energy content of the diet was not lower than 13.5 MJ kg^?1. Dietary energy levels below 13.5MJ kg^‐1 resulted in significant reductions in shell growth, weight gain and increased mortality from 5% to 27%. Feed consumption of the 22% and 26% protein diets with 11.6 MJ kg^?1 was significantly higher (0.53 ± 0.04 and 0.55 ± 0.04% bd. wt. day^?1 respectively) compared with abalone fed the 16.2 MJ kg^?1 diets at the same protein levels (combined mean of 0.45 ± 0.04% bd. wt. day^?1) indicating that consumption was linked to energy requirement. The growth and mortality results suggest that abalone cultured at these temperatures have a dietary digestible energy requirement of at least 13.5 MJ kg^?1.     

The effect of light intensity on growth of juvenile dusky kob Argyrosomus japonicus (Temminck & Schlegel 1843)

South African juvenile dusky kob Argyrosomus japonicus are more abundant in turbid estuaries than in clear marine‐dominated estuaries. Turbidity can reduce light penetration into the water and create an environment different from that experienced by fish under culture conditions in mechanically filtered clear water. In order to optimize rearing conditions of this species, the effects of light intensity (23–315 lx) and feeding method (restricted ration vs. feeding to apparent satiation) on growth and food conversion ratio (FCR) of juvenile A. japonicus were assessed in a 56‐day growth trial. Fish weight increased from 7.2±1.6 to 41.9±10.2 g fish^?1 at a growth rate of 3.25% body weight day^?1. Light intensity did not significantly affect growth or FCR. Feeding method did not significantly affect growth rate, but average FCR was significantly better in treatments fed a ration of 3.6% body weight day^?1 than in treatments fed to apparent satiation. Therefore, a light intensity range of 23–315 lx can be used to culture dusky kob juveniles. The better FCR in fish fed a restricted ration suggests that a ration of 3.6% body mass day^?1 allowed good growth of juvenile dusky kob.     

Growth,partial energy balance,mantle and digestive gland lipid composition of Octopus vulgaris (Cuvier, 1797) fed with two artificial diets

Effects of two binders (gelatine and alginate) were tested on growth, survival, partial energy balance and lipid composition of mantle and digestive gland (DG) of Octopus vulgaris. The three diets tested were given as follows: CON, (Loligo gahi) as control, GEL, composed of squid paste (L. gahi) (300 g kg^?1), fish hydrolyse CPSP^® (100 g kg^?1) and fish meal (500 g kg^?1), agglutinated with 100 g kg^?1 of gelatine and ALG, composed of squid paste (L. gahi) (300 g kg^?1), fish hydrolyse CPSP^® (100 g kg^?1) and fish meal (500 g kg^?1), all agglutinated with 100 g kg^?1 of alginate. Growth rates were 13.7 ± 2.1, 2.1 ± 2.8 and ?2.4 ± 2.9 g kg^?1 bw day^?1, for octopuses fed CON, GEL and ALG diets, respectively. DGs of octopuses had higher concentrations of fatty acids (FA) than the mantle. DG of animals fed CON had higher concentrations of FAs than those fed the artificial diets. Energetic balance demonstrated that physiologically useful energy for maintenance E(B) was affected by type of diet, with negative values of E(B) in animals fed ALG and positive (85 and 154 kJ kg^?1 day^?1) in octopuses fed GEL and CON, respectively. The ALG diet did not cope with the physiological requirements for octopus growth.     

Temperature and size range for the transport of juvenile donkey's ear abalone Haliotis asinina Linne

Live transport of hatchery‐produced juvenile donkey's ear abalone Haliotis asinina Linne was examined to evaluate the effect of transportation on the survival of juvenile abalone. Simulated transport experiments were conducted to determine the appropriate temperature using 5, 10 and 20 g L^?1 of ice to air volume for 8 h and the appropriate size using two size groups (Size A, 15–20 mm, 0.5–1.3 g, and Size B, 30–35 mm, 5.3–8.5 g) up to 24‐h out‐of‐water live transport. Survival was significantly higher (P<0.001) when 10 g L^?1 of ice was used to decrease the temperature to the range of 17–23 °C. At this temperature, both size groups subjected to simulated transport for 8 and 10 h had 100% survival after 48 h, while mortality occurred in abalones subjected to 16 and 24 h of simulated transport. The Size B abalone subjected to 24 h of transport had significantly higher survival (64.4 ± 2.9%) (P<0.001) than the Size A abalone (5.5 ± 1.6%) after 48 h. Live juvenile abalone were successfully transported to the field applying the protocols developed in the lab experiment. This study serves as a guide for handling and shipping live juvenile abalone.     

Growth performance of disk abalone Haliotis discus hannai in pilot- and commercial-scale recirculating aquaculture systems

The study investigated the growth performance of abalone from juvenile to marketable size in a commercial-scale recirculating aquaculture system. The rearing system consisted of 12 raceways (4.0 × 0.8 × 0.6 m) with a protein skimmer and a submerged biofilter for juveniles and 10 raceways (6.6 × 1.3 × 0.6 m) with a protein skimmer and a trickling biofilter for on-growing. Sea mustard (Undaria pinnatifida) and kelp (Laminaria japonica) were fed to the abalone. The total weight of abalone in the recirculating aquaculture system at the juvenile stage increased from 22.0 kg (average shell length 24.5 mm) to 75.5 kg (average shell length 42.5 mm) after 180 days. Feed conversion ratios increased slightly from 13.7 for the first 90 days to 16.3 thereafter. The shell growth rate of juvenile abalone between 24.5 mm and 34.8 mm was 3.4 mm month⁻¹, while for juveniles between 34.8 mm and 42.5 mm it was 2.6 mm month⁻¹. The total weight of abalone in the recirculating aquaculture system for the on-growing stage increased from 100.0 kg (average shell length 44.0 mm) to 433.3 kg (average shell length 72.7 mm) after 570 days. The feed conversion ratios for the first 173 days, the next 320 days, and the last 570 days were 19.6, 22.1, and 24.8, respectively. The growth rate of the average shell length during the on-growing period was 1.5 mm month⁻¹. Total ammonia nitrogen (TAN) concentrations were stabilized below 0.12 mg l⁻¹ in the juvenile recirculating system and 0.14 mg l⁻¹ in the on-growing recirculating system after conditioning of the biofilters.     

Combined effects of photoperiod and temperature on growth and survival of African catfish (Clarias gariepinus,Burchell 1822) larvae under laboratory conditions

ABSTRACT

The effect of photoperiod (24L:00D, 12L:12D, and 00L:24D) and temperature (22 ± 1°C and 28 ± 1°C) on performance of Clarias gariepinus larvae was tested. Larvae weighing 3.2 ± 0.24 mg were cultured in aquaria at a stocking density of 20 fish L^?1 and fed twice a day on catfish starter diet (40% CP) at 10 % BW day^?1. Highest mean weight gain (31.00 mg), SGR (7.56% day^?1), and survival (83%) were achieved at photoperiod and temperature combination of 00L:24D and 28 ± 1°C. Percent survival of larvae differed significantly (p < .05) among treatments with optimal survival of (83%) in treatment combination of 28 ± 1°C and 00L:24D, while lowest survival (40%) in treatment combination of 22 ± 1°C and 24L:00D.     

Effects of feeding rate and frequency on growth performance,digestion and nutrients balances of Atlantic salmon (Salmo salar) in recirculating aquaculture systems (RAS)

A 10‐week study was conducted to investigate the effects of feeding rate and frequency on growth performance, digestion and nutrients balances of Atlantic salmon (Salmo salar) in replicated recirculating aquaculture systems (RAS). Replicated groups of juvenile salmon weighing 90 ± 2.5 g (mean ± SD) were fed a commercial feed (21.63 MJ kg^?1 gross energy) to designed feeding rate (1.4%, 1.6% and 1.8% body weight day^?1, BW day^?1) and feeding frequency (2 and 4 meals day^?1) combinations. Specific growth ratio varied between 1.15 ± 0.02 and 1.37 ± 0.16% day^?1, and feed conversion ratio ranged from 0.96 ± 0.03 to 1.16 ± 0.02. The nitrogen and phosphorus retention rates were from 36.50 ± 1.94 to 47.08 ± 5.23% and from 20.42 ± 1.05 to 38.59 ± 2.80%. Apparent digestibility coefficients (ADC) in dry matter, protein, lipid and energy showed no significant differences for all groups. However, fish fed at 1.6% BW day^?1 and 4 meal day^?1 groups had relatively better growth and nutrient retention efficiency compared to other groups. In addition, concentrations of nitrogenous and phosphorous compounds were also detected in this study. These results suggested that salmon of 100–200 g in RAS could in practice be fed at 1.6% BW day^?1 and 4 meals day^?1, taking environmental impacts into account.     

Grow-out culture of tropical abalone, Haliotis asinina (Linnaeus) in suspended mesh cages with different shelter surface areas

Thisstudy investigated the effects of shelter surface area (SSA) on the feeding,growth and survival of the donkey-ear abalone, Haliotisasinina reared in mesh cages (0.38×0.38×0.28m) suspended in flow-through tanks (water volume = 6m³). Cages had sections of polyvinylchloride (PVC) thatprovided shelters with surface area of 0.22 m², 0.44m² and 0.66 m².Hatchery-produced abalone with initial shell length of 32 ± 1mm and wet weight of 7.5 g were stocked at 50individuals cage^?1 that corresponded to stocking densities ofca. 227, 113 and 75 abalone m^?2 of SSA. The ratios of sheltersurface area to cage volume (SSA:CV) were 5.5, 11 and 16.5. Abalones wereprovided an excess red seaweed Gracilariopsis bailinae(= Gracilaria heteroclada) at weekly intervals overa 270-day culture period. Feeding rates (18–20% of wet weight), foodconversion ratio (26–27) and percent survival (88–92%) did notdiffer significantly among treatments (p > 0.05). Body size at harvest rangedfrom 56 to 59 mm SL and 52 to 57 g wet body weightwith significant differences between abalone reared at SSA 0.22m² and 0.66 m² (p < 0.05).Abalone reared in cages with 0.66 m² SSA grewsignificantly faster at average daily growth rates of 132 μm and188 mg day^?1. Stocking densities of 75–113m^?2 SSA in mesh cages suspended in flow-throughtanks resulted in better growth of abalone fed red seaweed.     

Optimum feeding rates in juvenile olive flounder,Paralichthys olivaceus,at the optimum rearing temperature

Two feeding trials were carried out to determine the optimum feeding rates in juvenile olive flounder, Paralichthys olivaceus, at the optimum rearing temperature. Fish averaging 5.0 ± 0.11 g (mean ± SD) in experiment 1 and 20.2 ± 0.54 g (mean ± SD) in experiment 2 were fed a commercial diet at the feeding rates of 0%, 3.0%, 4.0%, 4.25%, 4.5% and 4.75% body weight (BW) day^?1 and satiation (5.52% BW day^?1) in experiment 1 and 0%, 1.0%, 2.0%, 3.0% and 3.5% BW day^?1 and satiation (4.12% BW day^?1) in experiment 2 at 20 ± 1 °C. Both feeding trials lasted for 2 weeks. Results from experiment 1 indicated that weight gain (WG) and specific growth rate (SGR) of fish fed to satiation were significantly higher than those of fish fed at other feeding rates while feed efficiency (FE) and protein efficiency ratio (PER) of fish fed at 4.25% BW day^?1 were significantly higher than those of fish fed to satiation and fish fed at 3.0% BW day^?1 (P < 0.05). In experiment 2 WG, SGR and PER leveled out after the feeding rate of 3.5% BW day^?1 whereas FE reached a plateau at 3.0% BW day^?1. anova of FE indicated that the optimum feeding rates in 5.0 and 20 g juvenile olive flounder could be 4.25% and 3.0% BW day^?1, respectively. Broken line analysis of WG suggested the optimum feeding rates of 5.17% and 3.47% BW day^?1 in 5.0 and 20 g fish, respectively. Therefore, these results indicated that the optimum feeding rates could be >4.25 but <5.17% BW day^?1 for 5.0 g, and it could be >3.0 but <3.47% BW day^?1 for 20 g size of juvenile olive flounder at the optimum rearing temperature.     

The effects of feeding frequency on growth of juvenile Atlantic halibut, Hippoglossus hippoglossus L.

Four experiments were conducted to investigate the effects of feeding frequency on growth of juvenile Atlantic halibut, Hippoglossus hippoglossus L. Fish (22–75 g) fed three (3 ×) or five times per day (5 × day^?1) under constant light and temperature (13±1°C) consumed significantly more feed than fish fed 1 × day^?1 but by the end of the experiment only fish fed 5 × day^?1 were heavier and had greater specific growth rates (SGR). Under simulated winter conditions (9L:15D, 5±1°C), halibut (～300 g) fed every other day consumed more feed, had a greater SGR and final weight compared with fish fed every third day. Feed conversion ratios were not different among treatment groups in any of the experiments. These results suggest that growth rates may be improved by feeding juvenile halibut more than 1 × day^?1.     

The proteolytic digestive activity and growth during ontogeny of Parachromis dovii larvae (Pisces: Cichlidae) using two feeding protocols

The proteolytic digestive activity and growth of Parachromis dovii larvae during the ontogeny were evaluated in a recirculation system using two feeding strategies during a 28-day period. Larvae were reared using two feeding protocols (three replicates each): (A) Artemia nauplii (at satiation), fed from exogenous feeding [8 days after hatching (DAH)] until 15 DAH followed by nauplii substitution by formulated feed (20 % day^?1) until 20 DAH and then formulated feed until 28 DAH; (B) formulated feed (100 % BW daily) from exogenous feeding until 28 DAH. Levels of acid (pepsin type) and alkaline digestive proteases as well as growth and survival of larvae were measured along the feeding period. Survival was high and similar between treatments: 98.9 ± 0.0 for Artemia, 97.3 ± 0.0 % for formulated feed. The specific growth rate for length and weight was higher in larvae fed with Artemia nauplii than in larvae reared with formulated feed: 3.4 ± 0.1 versus 1.8 ± 0.1 % day^?1 for body length (P = 0.009) and 12.2 ± 0.1 versus 6.5 ± 0.3 % day^?1 for body weight (P = 0.002). The acid and alkaline proteolytic activity was detected, in both treatments, from the beginning of the experiment, at 8 DAH. The total enzymatic activity (U larva^?1) for acid and alkaline proteases was higher in larvae reared with Artemia after 12 DAH, whereas the specific enzymatic activity was similar for both enzyme types in the two treatments. The results suggest that P. dovii larvae were capable to digest formulated diets from the beginning of exogenous feeding and that they could be reared with formulated feeds. However, the formulated feed used should be nutritionally improved because of the poor growth obtained in this research.     

Aspects of the growth of cultured cuttlefish Sepia officinalis (Linnaeus 1758)

Feeding rates, growth rates and feed efficiency ratios were studied in experimentally reared juvenile cuttlefish Sepia officinalis which had been hatched from eggs collected from three different locations, Plymouth, North Wales and Southampton. Groups of newly hatched cuttlefish were either maintained at 19°C and well fed (experiment 1) or were maintained at ambient seawater temperature (7–16°C) with little food for 6 months so that their development was delayed and then transferred to optimum conditions (experiment 2). In the first investigation (expt 1), no significant differences in growth rates (3.72±0.08%, 3.75±0.04% and 3.55±0.04% body weight (BW) day^?1 respectively), feeding rates (9.53±0.36%, 9.28±0.36% and 8.95±0.37% BW day^?1 respectively) and feed efficiency ratios (38.11±1.67%, 40.52±1.78% and 39.96±1.78% respectively) were observed between cuttlefish from the 3 locations. During the second investigation (expt 2), cuttlefish, whose development was initially delayed after hatching and then were stimulated to grow under optimum conditions (19°C and fed), showed growth rates (3.46±0.08% BW day^?1) similar to those held under optimum conditions of seawater temperature (19°C) and food supply shortly after hatching. Feeding rates and feed efficiency ratios were however significantly higher in cuttlefish maintained at 19°C compared to 11°C (8.27±0.14% BW day^?1, 41.25±0.52% and 2.75±0.09% BW day^?1, 24.87±1.87% respectively).