Opto-electronic counters for juveniles of macrobrachium rosenbergii (de Man): Supporting equipment and use of counter B under commercial hatchery conditions

To count postlarvae or juveniles of M. rosenbergii with the high speed opto-electronic Counter B, a clean water supply, a system for delivery of juveniles into the counting device, the collection of counted juveniles and partition of these into containers for delivery to ponds, are required. Juveniles are collected from rearing tanks without contamination by particles of detritus, which would otherwise be counted. The infrastructure, counter performance, juvenile handling procedures and survival tests done on machine-counted juveniles are described. Counting speed (juveniles per hour), counting errors and labour needs (men) are: 200 000, <1% and two for machine counting; 10 000, >2% and six for hand counting; a supervisor is required in both cases. Survival of machine-counted juveniles is the same as that of hand counted ones, indicating that the electronic counter and methods of using it have no adverse effects on juvenile prawns of this species. It is believed that this counter is unique, and that it has wide applicability to counting various aquatic organisms.     

Opto-electronic counters for postlarvae and juveniles of Macrobrachium rosenbergii (de Man); design and tests of Type B counter

The disadvantages of hand counting hatchery produced juveniles of Macrobrachium rosenbergii have been overcome by development of a high speed opto-electronic counter. The hydraulic, mechanical and electronic designs of the Type B counter are described. The counter, extremely fast in principle, is being used and tested under commercial hatchery conditions. Its practical speed of operation and accuracy are expected to exceed 100 000 juveniles per hour and 95%, respectively.About 80% of juveniles show some morphological damage but most of this probably originates in the hatchery rearing tanks. Tests show that slight additional damage is caused only to the antennules of juveniles passing through the counter but this does not affect their subsequent growth rate and survival. It is suggested that density dependent aggression in hatchery tanks is the principal cause of damage. Counter B is shown to be suitable and safe for counting freshwater prawn juveniles. This counter could be adapted to count other macroscopic aquatic organisms via suitable dimensional scaling. No other counters of this type and purpose appear to exist.     

Effect of antibiotic treatment on the growth and survival of juvenile northern Chilean scallop, Argopecten purpuratus Lamarck (1819), and associated microflora in experimental cultures

Juvenile northern Chilean scallops of 937±55 μm shell height were exposed to five different concentrations of chloramphenicol (CHL) (5, 10, 25, 50 and 100 μg mL⁻¹), plus a control without antibiotics. To determine the effect of CHL on the accompanying microflora, the number of colony-forming units (CFU) that grew on TGE culture medium was counted in the seawater of containers with juveniles, and in containers with microalgae used as food. Both were exposed to the same concentrations of CHL. The growth rates of juveniles treated with CHL and the control without antibiotic showed highly significant differences ( P =0.0001). The growth rate was inversely proportional to the CHL concentration. The control sample presented the highest growth rate (84.4±14.3 μm day⁻¹), followed by the sample treated with 5 μg mL⁻¹ (64.2±14.3 μm day⁻¹). The survival in the control and in the treated samples with 5–50 μg mL⁻¹ was rather high, with a mean value of 95%. Only the sample treated with 100 μg mL⁻¹ had a low survival (36.7%). The CFU count was larger in the containers with juveniles, when compared with the ones with food. The CFU count tended to decrease with increasing CHL concentration in the juveniles.     

Evaluation of a Mechanical Grader to Separate Fingerling Channel Catfish,Ictalurus punctatus,into Length Groups

A Fischtechnik fingerling grader and bioscanner counter were evaluated for speed and accuracy in grading and counting channel catfish, "Ictalurus punctatus," fingerlings. Channel catfish fingerlings ranging in total length from 90 to 280 mm were graded into 110- to 140-mm, 140- to 170-mm, 170- to 200-mm and >200-mm length groups and counted. A sample of the fingerlings was manually separated through grader boxes with 109 mm (7/16 inch), 141 mm (9/16 inch) and 172 mm (11/16 inch) bar spaces to compare length variation within size groups with the mechanical grader. The accuracy of the bioscanner counter was tested by comparison with hand countintg. Fingerlings weighing 679 kg were mechanically graded and counted in 56 minutes, a rate of 12.1 kg/minute. Standard deviation for length within size groups was 10.9, 13.5, and 24.0 mm for the 109-mm, 141-mm, and 172-mm grader boxes, respectively; and 13.4, 12.6, 13.0, and 16.4 mm for the 110- to 140-mm, 140- to 170-mm, 170- to 200-mm and >200-mm mechanical grader length categories, respectively. Length variance within size groups was statistically lower for the mechanical grader compared with the box graders (P < 0.05). The bioscanner counter averaged a 5% overcount of channel catfish fingerlings compared with the manual count (P < 0.05).     

The effect of shade on water quality parameters and survival and growth of juvenile fluted giant clams, Tridacna squamosa, cultured in a land-based growth trial

Juvenile fluted giant clams, Tridacna squamosa (mean shell length (SL) 15.7 ± 1.9 mm, mean total wet weight (TWW) 0.3 ± 0.1 g), were cultured for 4 months in land-based nursery tanks under four shade regimes (0, 10, 55 and 80 % shade). After 4 months, there were no significant differences in survival which ranged from 98.8 ± 0.1 % in juveniles cultured under 55 % shade to 100.0 ± 0.0 % in the other treatments. The SL of unshaded juveniles was only significantly greater than that of juveniles shaded 55 and 80 %. However, the TWW of juveniles cultured with no shade was significantly greater than that of the juveniles from all other treatments. The mean growth rate of juveniles varied from 5.0 mm month^?1 for juveniles shaded 80 % to 6.9 mm month^?1 for juveniles not shaded. There was no significant difference in mean growth rate of unshaded juveniles and juveniles shaded 10 %, but only the growth rate of juveniles cultured unshaded was significantly greater than that of juveniles shaded 55 and 80 %. The organic tissue content of juveniles cultured either unshaded or shaded 55 % was significantly higher than that of juveniles shaded 80 %. In contrast, the condition index (CI) of juveniles shaded 80 % was significantly higher than the CI of juveniles cultured either unshaded or shaded 55 %. However, there was no significant difference between the CI of juveniles shaded 80 and 10 %. Growth rate of juveniles was significantly correlated with temperature, dissolved oxygen content and flow rate of seawater. While low degrees of shade increase the growth rate of juvenile T. squamosa, they also negatively affect tissue condition. A shade level of 10 % appears to be optimal as it maximises growth and maintains a high CI.     

Individual food intake measurement of freshwater crayfish (Pacifastacus leniusculus Dana) juveniles

The inert marker method for individual food intake measurement of signal crayfish (Pacifastacus leniusculus Dana) juveniles (carapace length (CL) ranged from 16.5 to 25.6 mm and wet weight (WW) from 0.88 to 4.47 g) was evaluated in a series of experiments. The measurement technique was tested with two types of diet: a gelatin‐based semi‐moist diet and an agar‐based dry diet. Diets were labelled with X‐ray dense ballotini glass beads. After feeding, juveniles were X‐rayed, and the amount of ingested glass beads in the digestive track was counted from the X‐ray images. The method proved reliable only with the gelatin diet. In the ingested gelatin food, 92.80±8.55% of the glass beads originally in the food were found in comparison with 40.99±24.72% for the agar diet. Subsequently, the growth efficiency of the gelatin diet was compared with typically used raw fish diet (roach, Rutilus rutilus L.), and possible harmful effects of X‐raying on the growth and survival of the juveniles were tested on 2‐year‐old crayfish (CL 22.90±1.66 mm and WW 3.15±0.71 g). Roach‐fed juveniles grew significantly faster than the gelatin‐fed counterparts. However, the growth performance and survival of the juveniles on gelatin diet was considered good enough to allow long‐term growth experiments with individual feed intake monitoring, e.g. for studies on social behaviour of the crayfish. The results of this study confirmed that the X‐radiography technique together with a semi‐moist gelatin‐based diet makes it possible to measure individual food consumption of freshwater crayfish juveniles reared communally.     

温度对云南盘鮈仔稚鱼生长及存活率的影响

为探究不同温度对云南盘鮈(Discogobio yunnanensis)仔稚鱼生长及存活率的影响,实验设置14、17、20、23和26℃五个温度梯度,以刚出膜且发育正常的云南盘仔鱼为实验对象,定期观察仔稚鱼的生长发育情况并统计死亡数量,测定全长、体长、体重等生长参数。结果显示:温度显著影响云南盘鮈仔稚鱼的生长发育及存活。随着温度的升高,发育进程加快;实验结束时,23℃组云南盘鮈口吸盘最早发育完整,20℃组云南盘鮈存活率最高。在整个实验过程中,20、23和26℃组间全长和体重无显著性差异,说明这几个温度对云南盘的全长、体重生长产生的效应大致相同。综合多种因素考虑,建议在实际生产中,以20~26℃作为云南盘的养殖温度。     

FOOD AND FEEDING STRATEGIES IN CULTURE OF LARVAL AND EARLY JUVENILE PURPLE-HINGE ROCK SCALLOPS,Hinnites multirugosus (GALE)

The purple-hinge rock scallop is receiving increasing interest as a candidate for commercial mariculture. Hatchery culture of juveniles is prerequisite since natural recruitment of juveniles is variable and not dependable as a source of stock. Success in carrying larvae through metamorphosis has been limited. Critical to larval culture is a sound understanding of optimal food and feeding strategies. Growth and survival were examined in early larvae fed six algal diets at four separate concentrations. The data clearly illustrate the superiority of both Isochrysis galbana and a Tahitian (T) strain of Isochrysis. Feed concentrations of 1 × 10⁵ cells/ml were found to be optimal for these species of Isochrysis. An I. galbana diet supported 80% survival through metamorphosis. The other algae examined included Mono-chrysis lutheri, Rhodomonas sp., Carteria pallida, and a 1:1:1 mixture of Rhodomonas, Monochrysis, and Isochrysis. All these diets supported 5–6% survival, and the growth was only slightly better than starvation controls. A similar study was done with early juveniles (1 mm dia). The diets included: I. galbana, M. lutheri, Thalassiosira pseudonana (3H), T-Isochrysis sp., and Phaedactylum tricornutum. As with the larvae, superior growth and survival occurred with diets of both species of Isochrysis. Cell concentrations between 1 × 10⁵ and 2 × 10⁵ cells/ml were optimal. The other diets supported minimal growth. In the feeding runs of both larvae and early juveniles, cell densities in excess of 5 × 10⁵ cells/ml were detrimental.     

Growth rates and survival of western rock lobster (Panulirus cygnus) at two temperatures (ambient and 23 °C) and two feeding frequencies

Wild caught post-pueruli, year one and year two post settlement juvenile western rock lobster, Panulirus cygnus, were held at ambient temperatures (15.6 °C to 23.1 °C; mean 19.0 ± 0.07 °C) or at 23 °C, and fed the same ration of a formulated pellet diet either once per night, or 3 times per night, over 12 months, to determine whether elevated temperatures and multiple feeds per night would stimulate growth through increased metabolism and feed utilisation without significant negative impacts on survival. Survival of post-pueruli (mean 63%) did not differ between ambient and 23 °C. Survival of year 1 and 2 juveniles was higher at ambient temperatures (p < 0.01 ambient: year 1 juveniles, 68%; year 2 juveniles, 88%; 23 °C: 57% and 74%, respectively). Feeding frequency did not affect survival of post-pueruli and year 2 juveniles (mean 63%, 81% respectively), but survival was 9% higher for year 1 juveniles fed three times per night (58% versus 67%; p < 0.01). All lobsters grew faster at 23 °C than at ambient temperatures (p < 0.05), with the growth of post-pueruli almost doubled at 23 °C (weight gain at 23 °C versus ambient: post-pueruli, 18 438 % versus 9 915 %; year 1 juveniles 259% versus 165%; year 2 juveniles 23% versus 21%). Feed frequency did not influence the growth of year 1 and 2 juveniles. However, there was an interaction effect of temperature and feed frequency on post-pueruli where weight and carapace length were significantly higher at ambient temperatures when post-pueruli were fed three times a day, whereas at 23 °C weight and carapace length were significantly greater when fed once per day (p < 0.05). Feed intake (g pellet dry matter lobster^− 1 day^− 1) of pellet was higher at 23 °C for all lobsters (p < 0.05), but was the same between lobsters fed 3 times per night versus once per night. This study has shown that increasing temperatures to 23 °C significantly improved the growth of P. cygnus post-pueruli without any adverse effects on survival. The faster growth rates exhibited by year 1 and 2 juveniles at 23 °C may potentially offset their lower survival by significantly reducing culture period. There is no benefit of feeding P. cygnus multiple times at night in terms of growth and survival. The implications for P. cygnus culture are that temperatures should be maintained close to 23 °C during the entire growout period, with due care taken to minimise mortalities through adequate provision of food and shelter. Feeding P. cygnus once daily to excess just prior to dusk to co-incide with nocturnal feeding behaviour is recommended.     

An automatic counting system for transparent pelagic fish eggs based on computer vision

Alive eggs of marine species with pelagic eggs float, while dead eggs usually sink. A non-invasive method for counting the number of floating eggs therefore gives the possibility to track survival throughout experiments. In this paper we present an automatic image analysis method for counting live pelagic eggs of marine fish. Pelagic fish eggs are typically transparent and difficult to detect in images. Current image analysis methods for counting pelagic fish eggs are therefore done on eggs transfixed in a polymer to create contrast between the eggs and the background. This kills the eggs. The main advantage of the presented method is that it is non-invasive and only requires a minimum of handling of the eggs. As case studies we collected images of Atlantic haddock (Melanogrammus aeglefinus) and Atlantic cod (Gadus morhua) eggs. The eggs in the images were manually counted for verification of the methodology. The average counting error of false positives was 6% and the average counting error of false negatives was 2%. This demonstrates that the method is objective and accurate.     

Effects of shelter on growth and survival in age-0 black sea bass, Centropristis striata (L.)

Black sea bass Centropristis striata (L.) juveniles were reared in aquaria containing either shelter or no shelter to investigate the effects of shelter on growth and survival. The specific growth rates of juveniles were significantly higher in the sheltered aquaria. With shelter present, the average mortality of juveniles caused by agonistic behaviour was 44% compared with no mortality in the unsheltered aquaria. The results provide evidence that shelter is advantageous for growth, but not survival of black sea bass juveniles under culture conditions.     

Culture of juvenile European lobster (<Emphasis Type="Italic">Homarus gammarus</Emphasis> L.) in submerged cages

A bottleneck for re-establishment or enhancement of lobster (Homarus gammarus L.) populations through release of hatchery-produced juveniles is ineffective and expensive juvenile production. In this study, we cultured lobster juveniles from stage V to a size being suitable for re-establishment or enhancement purposes (40–50 mm total length) in cages submerged under existing facilities for culture of bivalves. The lobsters were not feed or tended during the culture period (6–14 months). The survival and growth rates were similar or higher compared to what has been achieved with other methods used for culture of lobster juveniles in the past. The highest survival (82–89%) and fastest growth (4–5 cm total length over 190–250 days) were achieved using commercial oyster baskets. It is believed that the juveniles fed on naturally occurring plankton and organisms growing inside the cages. Thus, the current study shows that it is possible to culture lobster juveniles for reestablishment or enhancement purposes in a way that would involve less investments and operational costs than earlier used methods as there would be no need for artificial heating of water, for large buildings or for continuous feeding and tending of large numbers of juveniles.     

A Comparison of Growth,Survival, and Fatty Acid Composition of the Lined Seahorse,Hippocampus erectus,Juveniles Fed Enriched Artemia and a Calanoid Copepod,Schmackeria dubia

The purpose of this study was to evaluate the effect of varying dietary levels of highly unsaturated fatty acids (HUFAs) in live prey (Artemia nauplii and a calanoid copepod, Schmackeria dubia) on the growth performance, survival, and fatty acid composition of the lined seahorse, Hippocampus erectus, juveniles. Artemia nauplii were enriched with a commercial product (SS^? 50DE‐microcapsule as HUFA source, 2/3 DHA, 1/3 EPA. Shengsuo Fishery Feed Research Center of Shandong Province, Qingdao, China) at four concentrations of 0.0, 14.0, 28.0, and 56.0. Newly hatched juveniles were cultured for 35 days. The content of docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA), and n‐3 HUFAs in the Artemia nauplii was positively related to the enrichment concentration. At the end of the trials, growth performance of the juveniles was positively related to the enrichment concentration as well. However, the juveniles fed prey enriched with the highest concentration of enrichment (56.0 μL/L) had the significantly lower (P < 0.05) survival rate. The juveniles fed the copepod had the best growth performance and the highest survival rate, suggesting that the copepod, S. dubia, is suitable for feeding the seahorse juveniles. The comparisons between the growth, survival, and fatty acid profiles of the juveniles fed Artemia and copepods indicate that the seahorse juveniles require dietary levels of DHA beyond those achieved by enriching prey with the HUFA enrichment. Surplus EPA resulted from an imbalance between DHA and EPA in the enriched Artemia nauplii probably caused an adverse effect on the seahorse juveniles. This study suggests that DHA and EPA requirement of the lined seahorse juveniles is roughly 32% of total fatty acid, and the optimal DHA/EPA ratio for the species is circa 4:1. To avoid an adverse effect resulting from excessive EPA, maximum proportion of EPA in enriched Artemia nauplii should not exceed 13% of total fatty acid, and a recommended minimum DHA/EPA ratio in the enriched Artemia nauplii is 1.46. Arachidonic acid (20:4n‐6) might not be an essential fatty acid for the seahorse juveniles.     

A comparison of artificial and natural foods and their combinations in the rearing of goldfish, Carassius auratus (L.)

Intensive grow‐out of goldfish, Carassius auratus (L.), larvae and juveniles in closed systems requires the control of environmental conditions and feeding. This study investigates the use of different types of live food and combinations of live food and dry food in a series of four rearing experiments. Juvenile goldfish can be weaned from Artemia onto live food at about 24 days after the onset of feeding without causing a reduction in growth and survival. The replacement of Artemia by Daphnia at day 10 appears feasible, as growth and survival were not significantly affected. Fish fed decapsulated Artemia cysts grew better than fish fed live Artemia. Within the first 14 days, goldfish juveniles should be fed at least 155 cysts per fish per day to achieve fast growth and to minimize size variation.     

熊本牡蛎中国群体与美国群体杂交效应及杂交三倍体优势分析

为了评估熊本牡蛎(Crassostreasikamea)中国群体与美国群体的杂交效应与杂交三倍体优势,构建了杂交群体和自交群体,并使用细胞松弛素B诱导了杂交三倍体,比较分析了幼虫、稚贝与成贝的生长与存活优势。自交群体和杂交群体的幼虫、稚贝与成贝的培养条件均相同,室内培育幼虫,培育密度为4～5个/mL,自然海区养殖稚贝与成贝,养殖密度为40～45个/吊。结果表明,与自交组相比,杂交二倍体具有较高的卵裂率(13.61%)与D幼率(5.67%)(P0.05),但杂交二倍体幼虫的壳高生长表现杂种劣势(–0.43%),而稚贝、成贝的壳长与壳高的生长表现杂种优势,平均优势率分别为3.96%与6.65%。杂交三倍体诱导组幼虫的壳高生长优势率为3.69%,稚贝及成贝的壳长与壳高平均生长优势率分别为12.69%与13.64%,并且日龄越大生长优势越显著。总体上,杂交三倍体诱导组在3～180日龄具有存活劣势,并且15日龄存活劣势率最大(–48.72%),而在360日龄存活优势率为6.70%。杂交二倍体幼虫与成贝均具有存活优势,平均优势率分别为10.44%与4.59%。本研究表明熊本牡蛎中美地理群体杂交二倍体的生长和存活优于自交二倍体,而杂交三倍体诱导组的生长优势较显著,并且在成贝期具有显著的成活率优势,表明杂交三倍体诱导组的优势来源于三倍体优势和部分杂种优势。     

A method to eliminate self-fertilization in a simultaneous hermaphrodite scallop. 1. Effects on growth and survival of larvae and juveniles

Argopecten purpuratus, as several other scallops of commercial importance is a functional hermaphrodite. The usual methods for breeding cause an unavoidable degree of self-fertilization with the subsequent deleterious effects on survival and growth rates. Some researchers have unsuccessfully attempted to eliminate self-fertilization in these bivalves. Applying our knowledge of the cellular mechanisms of spawning in this species we have developed a method by which self-fertilization was eliminated. By this in vitro fertilization method, oocytes were obtained by scraping the female portion of the gonad, meiosis resumption was induced by serotonin, and then the oocytes were fertilized with sperm from different individuals. The progeny obtained by this method were compared with others obtained by cross-fertilization and self-fertilization. In all these procedures, the oocytes were fertilized at a ratio of 60 sperm per oocyte. The fertilization rates and D larvae survival were determined at 2 and 48 h, respectively. After the D larval stage, the hatchery culture of larvae continued as usual with sampling for survival and growth rates every three days. When larvae looked ready to settle and metamorphose, netlon collectors were introduced into the tanks. After 12 days the collectors were placed in 1 mm mesh collection bags and transferred to the sea. Juveniles were brought back to the hatchery every 40-70 days, to be counted, measured, and placed in mesh pearl nets. The assay of the three procedures for fertilization showed similar fertilization rates but low survival for D larvae obtained from the in vitro method. However, this procedure resulted in the highest size and survival rates of larvae. Survival of juveniles coming from this fertilization procedure was also the highest. The growth of juveniles obtained by in vitro fertilization was also higher than that of those obtained by self-fertilization. We conclude that this in vitro fertilization procedure provides a methodology that results in higher survival and growth rates of juveniles than obtained by procedures involving any degree of inbreeding. This in vitro procedure should be applicable to other simultaneous hermaphroditic scallops.     

放养密度和饵料种类对中国大鲵幼苗存活与生长的影响

研究了放养密度和饵料种类对幼中国大鲵（Andrias davidianus）生长发育的影响,跟踪分析了自胚胎孵化至一龄幼鲵的存活与生长发育状况。结果表明,自胚胎孵化至一龄幼鲵的养殖密度为每0.1m210～20尾时,其成活率可达到100%,投放密度每0.1m2自20尾增加到60尾,平均存活率、年体长增加和年体重增加均显著降低。投喂摇蚊幼虫、猪肉、牛肉、羊肉和小鱼虾,幼苗的存活率分别为100%、90%、95%、85%和95%,体长增加分别为8.09cm、5.45cm、5.28cm、4.57cm、6.82cm,体重增加分别为25.97g、12.68g、11.82g、10.86g和20.67g。可见,摇蚊幼虫和小鱼虾是一龄幼大鲵的适宜饵料。     

Evaluation of the growth and survival rate of the Caribbean Sea cucumber,Isostichopus badionotus (Selenka, 1867), early juveniles produced in captivity

Isostichopus badionotus is a new commercially important sea cucumber in the Caribbean that has rapidly shown signs of overexploitation. There is no information on the growth and survival rates for wild or hatchery‐produced early juveniles. Hatchery production and determination of juvenile growth rates are essential for future aquaculture efforts for this species. In this study, daily growth rate (GR), specific growth rate (SGR), weight gain (WG), survival rate (SR), and weight–length relation (WLR) were evaluated using small (0.01 g) and large (0.25 g) hatchery‐produced early juveniles under laboratory conditions. Growth was rapid compared to other cultured sea cucumber species; maximal values of SGR and WG were obtained for small juveniles (4.58%/day and 2,191%, respectively), while maximal GR and SR were obtained for large juveniles (0.29 mm/day and 99.17%, respectively). A wide range of sizes was evident at the end of each trial. The WLR of small and large juveniles fit with a negative allometric growth trend. This study highlights the potential production of I. badionotus as early juvenile stages withstand hatchery handling well and exhibit a high SR, reaching commonly released mean sizes (>0.7 g and 25 mm) after almost 3 months (120 days postfertilization).     

Laboratory trials on the effects of different diets on growth and survival of the common whelk, Buccinum undatum L. 1758, as a candidate species for aquaculture

Newly hatched juvenile Buccinum undatum can be reared under laboratory conditions. Good was growth is achieved when juveniles were fed on combined diets (blue mussel, cod, and fish pellets). Juveniles reached shell heights of 33.0 ± 4.2 mm, 26.9 ± 3.8 ± mm, 23.2 ± 2.2 mm, and 20.1 ± 1.6 mm, after 14 months of fedding on a combined diet, blue mussel, cod, and fish pellets, respectively under ambient sea temperature and salinity. After 14 months juveniles fed blue mussel had the highest survival rates (67%) followed by those fed a combination of all other experimental diets (61%), cod waste (53%) and fish-feed pellets (46%). High mortalities were recorded in most treatments during the summer months between June and September. This species appears to have an aquaculture potential, as juveniles readily feed on artificial diets at an early age, show high survival rates and could potentially reach market size in 2 years or less. The major constraint in realising this potential at present, is the relatively low value of the species; if market values increased as a result of serious depletion of natural populations, hatchery production of juveniles for intensive aquaculture or restocking could become economically viable.     

Growth and survival of juvenile seahorse Hippocampus abdominalis reared on live, frozen and artificial foods

The culture of seahorses has usually relied on cultured live foods or collected wild live foods as feed. This can be expensive in the case of culturing live foods and unreliable in the case of harvesting wild live foods. This investigation examined whether juvenile Hippocampus abdominalis from 0 to 2 months of age could be experimentally weaned onto frozen (Cyclop-eeze copepods) and artificial (Golden Pearls) food over 30-day periods with Artemia as a live food control, with 0-, 5-, 10-, and 20-day mixed feeding periods. Newborn juveniles could not be weaned onto Golden Pearls, with almost complete mortality. One-month-old juveniles could be weaned onto Cyclop-eeze with no effect on survival but with lower growth. One-month-old juveniles could be weaned onto Golden Pearls but with lower survival and lower growth. Two-month-old juveniles could be weaned onto Cyclop-eeze but with lower survival and lower growth. Two-month-old juveniles could be weaned onto Golden Pearls with no effect on survival but with lower growth. In all experiments, the rate of feeding strikes on Cyclop-eeze and Golden Pearls was lower than that on Artemia (e.g. range of mean 0.16–0.97 vs. 2.2–2.76 feeding strikes/min), both when Artemia were the sole food presented and when Artemia were cofed with the nonlive foods. However, mixed feeding Artemia with nonlive foods did appear to increase the rate of feeding strikes on nonlive foods. These results indicate the potential for incorporating more cost effective and reliable nonlive foods into seahorse culture.