Growth of Red Abalone,Haliotis rufescens,Fed Cold‐stored Benthic Diatoms

We measured the proximal composition of four benthic diatoms that were stored for 24 mo in the dark at low temperature (4 C by refrigeration) and examined their potential as feed for abalone, Haliotis rufescens, postlarvae. The proximal composition of the four diatoms was modified by species‐specific responses as a function of time in storage. The cultures of all stored diatoms contained low or undetectable concentrations of Vibrio‐like bacteria (<0.01 VLB/mL). As feed for abalone postlarvae, the four diatoms promoted growth under all experimental conditions. Greater shell lengths were measured on Day 14 when Navicula sp. and Navicula incerta were used as feed. Postlarvae that were fed N. incerta and Navicula sp. had higher growth rates. In contrast, lower growth rates were observed on Day 7 with fresh and stored Nitzschia thermalis as food. Survival was high in postlarvae that were fed the four stored diatoms (100%). This report demonstrates that cultures of benthic diatoms that have been stored by refrigeration for 24 mo can be used to feed abalone postlarvae and have an effect on improving growth and survival.     

The use of diatom Skeletonema costatum on aquaculture‐produced purple sea urchin (Paracentrotus lividus) larvae and post‐larvae diet

The quality of the microalgae provided on Paracentrotus lividus larvae rearing is a primordial factor having a direct (nutritional properties) and indirect (water quality) impact on growth, competence and survival. Skeletonema costatum is a diatom commonly used in the bivalve cultivation. However, the use of this diatom in P. lividus larval cultivations is poorly known. The Rhodomonas spp. is a microalgae commonly used in sea urchin larvae culture. Three different diets were tested on P. lividus larvae and post‐larvae cultivation (D1—Rhodomonas marina, D2—S. costatum, D3—mixture of both algae). Larvae fed with the D2 diet (55.8%) and D3 (39.9%) had a survival at 15 DAH higher than D1 (5.5%). The low survival in D1 could be due to the higher microbiological load on microalgae (Vibrio alginolyticus and V. pectenicide). Larvae fed with S. costatum (D2) showed a lower development than other diets. The competency index was lower for larvae fed with the D2. These results show that microalgae diversified diets contribute to a better development of P. lividus larvae. During the settlement and post‐settlement phase, there was also a lower growth of the sea urchin fed with the D2 and a higher survival for D3.     

Feeding of the short-spined sea urchin <Emphasis Type="Italic">Strongylocentrotus intermedius</Emphasis> on macroalgae and benthic animals

To examine the feeding ecology of the sea urchin Strongylocentrotus intermedius, two types of macroalgal diet (kelp Saccharina longissima and red alga Ptilota filicina) and four types of benthic animal diet [barnacle Balanus glandula, limpet Lottia cassis, free-living Perinereis aibuhitensis and P. aibuhitensis attached to a stainless steel wire (wired polychaete)], were separately or simultaneously provided for urchins of 5- to 60-mm test diameter (TD). Sea urchins of even 3-mm TD could graze the kelp, and began to graze the red alga, the wired polychaete and limpet by 5-mm TD, the barnacle by 8-mm TD and the free-living polychaete by 15-mm TD, respectively. These results suggest that the variety of macroalgae and benthic animals which the urchin can graze increases with the ontogeny of their feeding organs, motility and ability to catch animals. Both juvenile and adult sea urchins preferred to eat the polychaete as well as the kelp fronds. Feed conversion efficiency and daily growth rate of the small sea urchins fed benthic animals like the polychaete were higher than those fed macroalgae. The sea urchins are likely to grow better when feeding on animals than on macroalgae, even in habitats where they can access adequate quantities of kelp.     

Long‐term Growth Study of Male and Female Green Sea Urchins,Strongylocentrotus droebachiensis,under Constant Light and Temperature Regime

Juvenile green sea urchins, Strongylocentrotus droebachiensis, with an initial mean test diameter of 9.5 mm (±1.2 SD) were held in the laboratory, in individual compartments and at constant temperatures (8.5 C) (n = 90) for a period of 99 wk. The animals were supplied with flow‐through sea water, and fed the Nofima sea urchin manufactured feed ad libitum. Growth, survival, feed intake, feed conversion ratio (FCR), and gonad index (GI) of the sea urchins were monitored during this period. The mortality was 11% throughout the experimental period. The test diameter (TD) increased significantly with time, best described by a polynomial equation (TD = 0.8756 + 0.584Time − 0.002Time², R² = 0.995). Sex was included as dummy variable, but did not contribute significantly; hence, there were no differences in growth trajectories between males and females. The study showed there were no significant differences in body wet weight or FCR between males and females. However at the end of the experiment the female urchins had a significantly higher GI of 31.1% (±4.4), compared with the male urchins which had an average GI of 26.8% (±5.4). In conclusion, the present study showed that male and female green sea urchins have the same growth capacity and feed convention ratio but by the end of the experiment the gonad index was significantly higher in female than male urchins.     

Effect of Lipid Source and Concentration on Somatic Growth of Juvenile Green Sea Urchins, Strongylocentrotus droebachiensis

Supplying juvenile sea urchins with an abundant supply of resources and essential nutrients for growth will facilitate somatic growth and, hence, improve the success of the sea urchin aquaculture industry. Lipids are essential in physical processes such as membrane production and are a concentrated source of energy. This study, using prepared diets, tested the effects of lipid sources containing different major fatty acids (i.e., n‐3 and/or n‐6) (Part 1) and lipid concentration (i.e., 1, 3, 7, and 10%) (Part 2) on the somatic (i.e., test or shell) growth of two size cohorts (7.0‐ and 15.3‐mm average initial test diameter [TD]) of juvenile green sea urchins, Strongylocentrotus droebachiensis. The growth of the sea urchins fed prepared diets was compared to the growth of sea urchins fed a kelp reference diet, Laminaria longicruris. After both feeding trials, the kelp‐fed sea urchins had superior test growth and were more similar in physical appearance to wild sea urchins (i.e., test color, spine length, and gonad color). The sea urchins fed the prepared diets had pale test color, short, stubby spines, and large, pale‐colored gonads compared to wild sea urchins. The smaller cohort of sea urchins grew at a faster rate, but growth patterns for both cohorts were similar. The juveniles fed the prepared diets (in both feeding trials) had high initial growth rates that decreased after approximately 100 d compared to the kelp‐fed juveniles. Differences in test growth were not shown to be affected by sea urchin size (i.e., similar results for both cohorts) or by differences in dietary lipid sources (i.e., the presence of n‐3 and/or n‐6 fatty acids). However, the sea urchins fed diets with lower lipid concentration (≤3%) had larger average TDs than those fed diets with higher lipid concentrations (≥7%). Differences in test growth and physical appearance among those fed the prepared diets and kelp may have been because of nutritional deficiencies in the prepared diets.     

Evaluation of dried macrophytes as an alternative diet for the rearing of the sea urchin Paracentrotus lividus (Lamarck, 1816)

The aim of this work was to assess the potential use of different dried macroalgae as food in the rearing of Paracentrotus lividus. Growth, consumption and food conversions were compared in adult sea urchins fed with fresh or dried thalli of four macroalgae species. Six experimental diets were tested: (a) fresh Palmaria palmata; (b) fresh Saccharina latissima; (c) dry P. palmata; (d) dry S. latissima; (e) dry Laminaria digitata and (f) dry Grateloupia turuturu. Linear growth rates were similar for all treatments. Specific growth rate was higher in sea urchins fed with fresh P. palmata, but no difference was found between animals fed with fresh S. latissima and those fed with dried diets. Regarding daily food consumption (DFC), sea urchins consumed the same amount of dried macroalgae as fresh but exhibited a higher food conversion efficiency (FCE) when fed with fresh P. palmata. However, this FCE was only significantly higher when compared to sea urchins fed with dry L. digitata. Dried G. turuturu is not a suitable diet due to its rapid degradation after rehydration. The results suggest that P. lividus adults can be reared on dried macroalgae thalli without detriment to their somatic growth, especially over short periods. The low cost of feeding sea urchins with this diet could help small shellfish farmers to diversify their production into echinoculture.     

Gonad quality of sea urchin Paracentrotus lividus cultured in an offshore pilot‐scale trial on the south‐east Italian coast

A pilot project aimed at testing roe enhancement strategies based on offshore Paracentrotus lividus cultures was conducted off the south‐east coast of Italy (Apulia Region). Adult sea urchins were reared in sea cages located 700 m offshore at a depth of 12 m for 3 months. The animals were fed once a week on two formulated diets, prepared mixing nutrients with agar 20 g/Kg and differing only in terms of the protein source: anchovy flour (Diet A) or krill flour (Diet K). At the end of the rearing trial, the gonad somatic index of sea urchins fed on formulated diets significantly exceeded that of wild sea urchins. Total FAA content in the gonads of wild sea urchins and Diet A‐fed sea urchins was similar, whereas in Diet K‐fed sea urchins it was significantly higher. In terms of fatty acids, the gonads contained SFAs, MUFAs and PUFAs. In visual and sensory assessment of gonads by panel test and electronic nose, the gonads of reared sea urchins were rated as being of better size, while no differences were recorded for coloration, taste and odour. This study shows that under these experimental conditions, commercial‐grade Paracentrotus lividus roe enhancement can be achieved after 3 months in sea cages.     

Effect of Protein Source and Concentration on Somatic Growth of Juvenile Green Sea Urchins Strongylocentrotus droebachiensis

Abstract— An important aspect in the development of any aquaculture industry is the maximization of juvenile somatic growth (i.e., body growth) to reduce production time and increase the size of the final product. In this study, green sea urchins Strongylocentrotus clroebachiensis were fed a prepared diet from 4 December 1998 to 10 September 1999 (i.e., 280 d) in a laboratory to investigate the effect of protein source (soybean andlor fish), protein concentration (20,30,40, and 50% dry mass) and juvenile size (4‐8 mm and 12‐20 mm initial test diameter) on somatic growth. A natural diet of Laminwia longicrurus (i.e., kelp) was used as a reference. There was no difference in initial size among the treatments for either the smaller cohort 1 or the larger cohort 2 sea urchins (6.3 mm and 13.8 mm initial average test diameter, respectively) (P > 0.05 for all tests). After 280 d, the sea urchins fed kelp had an average size of 20.7 mm and 24.5 mm (cohort 1 and cohort 2, respectively). The final average sizes of the sea urchins fed the prepared diets, which did not relate to dietary protein concentrations andlor protein source, ranged from 13.2 mm to 16.2 mm (cohort 1) and from 20.4 mm to 22.9 mm (cohort 2), and were significantly smaller than the kelpfed sea urchins (P < 0.05 and P < 0.001, cohort 1 and cohort 2, respectively). All treatments experienced 95% survivorship or greater. Sea urchin size appears to affect growth rate when optimal conditions for growth are available (i.e., diet and water temperature). As water temperatures increased during the summer of 1999, the sea urchins in cohort 1 fed kelp had a significantly higher growth rate (0.069 dd) than the cohort 2 kelpfed sea urchins (0.052 dd) (P < 0.05). However, within each cohort, there were no significant difference in growth rate (P > 0.05) among the sea urchins fed prepared diets, suggesting sea urchins do not require high concentrations of dietary protein for superior growth, and that plant protein can substitute fish protein in sea urchin diets. Furthermore, the sea urchins fed the prepared diets had poorer test quality and larger gonad yields (13‐22%) compared to the kelpfed sea urchins (4.2%) and a wild sample of sea urchins of similar size (4.0%). The results suggest that the sea urchins fed the prepared diets allocated more energy to gonad production, whereas those fed a natural diet allocated more energy toward test production. To address this gap, more research is required to identify the nutritional components required for test growth that were present in kelp, but appeared to be deficient in the prepared diets.     

Dietary value of gametophytes and juvenile sporophytes of the brown macroalga <Emphasis Type="Italic">Eisenia bicyclis</Emphasis> for juvenile abalone <Emphasis Type="Italic">Haliotis diversicolor</Emphasis>

The dietary value of juvenile stages (gametophyte and juvenile sporophyte) of the brown macroalga Eisenia bicyclis for post-larval and juvenile abalone Haliotis diversicolor of 2.0–6.5 mm in shell length (SL) was examined and compared with that of a benthic diatom, Nitzschia sp., in laboratory experiments. Most abalone actively fed on these diets, but there were large variations in the growth rate among the diets and among the growth stages of abalone. Growth rates of abalone fed on Nitzschia sp. were highly variable within each growth stage, but showed no clear differences among growth stages. In contrast, in abalone fed gametophytes or juvenile sporophytes, growth rates linearly increased as abalone grew. Growth rates of >60 μm SL/day were observed in juveniles of >3 mm SL fed gametophytes, and juveniles of >5 mm SL fed juvenile sporophytes. These results indicate that the dietary value of the juvenile stages of E. bicyclis for the abalone changes as they grow, and with growth juvenile abalone begin to efficiently utilize gametophytes and juvenile sporophytes in that order.     

Enhancement of survival and metamorphosis rates of <Emphasis Type="Italic">Penaeus monodon</Emphasis> larvae by feeding with the diatom <Emphasis Type="Italic">Thalassiosira weissflogii</Emphasis>

The purpose of this study was to compare the performance of two species of diatoms, Thalassiosira weissflogii and Chaetoceros gracilis, in the larviculture of the black tiger shrimp Penaeus monodon. Shrimp larvae were fed with either C. gracilis, T. weissflogii, or a combination of the two species of diatoms. The larvae fed solely with T. weissflogii or a combination of the two types of diatom had significantly higher survival rates and faster metamorphosis than those fed solely with C. gracilis. The numbers of diatom cells consumed by larvae during 3-h periods were determined, revealing that larvae consumed significantly higher numbers of C. gracilis than T. weissflogii. However, when the protein, total fatty acid, and polyunsaturated fatty acid content of the two species of diatom are compared, significantly higher amounts of each are found in T. weissflogii. Converting the number of diatom cells consumed into equivalent protein, total fatty acid, eicosopentaenoic acid, and decosahexaenoic acid reveals that larvae fed with T. weissflogii received significantly higher amounts of all the nutrients, compared to those consuming C. gracilis. The results showed an advantage of feeding T. weissflogii to C. gracilis in enhancing survival and metamorphosis in P. monodon larvae.     

Effect of Dietary Minerals and Pigment on Somatic Growth of Juvenile Green Sea Urchins, Strongylocentrotus droebachiensis

This study investigated the effects of dietary minerals and pigments in prepared diets on the somatic growth performance of wild and hatchery‐reared juvenile green sea urchins, Strongylocentrotus droebachiensis, by two feeding trials. In the first feeding trial, a modified Bernhart‐Tomerelli salt mix (BT) at 0, 1.5, 3, 6, and 15% dry mass and a Shur‐Gain/Maple Leaf Foods mineral mix at 3 and 6% dry mass were used to test for mineral effects. Pigment effects were tested by incorporating 1.25% Algro? to the prepared diets (i.e., 250 mg of beta‐carotene per kilogram of diet). Sea urchins (13–15 mm of initial test diameter [TD]) collected from the wild were fed the prepared diets over 154 d. The sea urchins that were fed the pigmented diets had significantly greater test growth than those fed the nonpigmented diets, and mineral concentration in the pigmented diets was directly related to juvenile size at the end of the feeding trial. A sample of juveniles from each treatment group was sacrificed to determine test, gonad, and gut yields and ash concentrations. Ash concentrations in the test and gonad were higher for juveniles fed pigmented diets than for those fed nonpigmented diets with similar mineral concentration, suggesting an interaction between minerals and pigments within the juvenile sea urchins. The second feeding trail used two size cohorts of hatchery‐reared juveniles ranging from 1–2 mm and 2–3 mm of initial TD to compare the growth of sea urchins fed either the pigmented diet with 15% BT (i.e., the best diet in the first feeding trial) or kelp, Laminaria longicruris, over 159 d. Growth performance was similar for both cohorts, indicating no size effect, but the juveniles fed the prepared diet were significantly larger at the end of the feeding trial than those fed kelp. This suggests that prepared diets with pigment and high mineral concentration can outperform kelp, and be utilized for juvenile green sea urchins to increase test growth.     

Settlement of larval top shell <Emphasis Type="Italic">Turbo (Batillus) cornutus</Emphasis> in response to several marine algae

ABSTRACT:     The settlement of larval top shell Turbo  ( Batillus )  cornutus in response to seven macroalgal and three benthic diatom species was examined in the laboratory. The percentages of larval settlement differed significantly among algal species, and were significantly higher on two red algal species ( Marginisporum crassissima , an articulated coralline alga, and Gelidium elegans , an agarophyte) than on the green algae, brown algae and benthic diatoms tested. Marginisporum crassissima induced larval settlement most strongly throughout the experiments. The percentage of larval settlement on a crustose coralline alga (unidentified species), which is known as a suitable substratum for abalone larvae, was much lower than on M. crassissima and G. elegans , which have morphologically complex growth forms . The percentage of settled individuals on ethanol-killed M. crassissima was much lower than on intact M. crassissima . The results indicate that physical structure is unlikely to be the main inducer of settlement; therefore, settlement of top shell larvae seems to be strongly induced by chemicals from the two red algal species. The specific distribution of juvenile top shell in the field may be at least partly determined by the strong induction of larval settlement by articulated coralline and gelidiacean algae.     

Effect of different feed formulations on feed efficiency, gonad yield and gonad quality in the purple sea urchin Heliocidaris erythrogramma

The nutritive values of three pelleted prepared diets, based on animal (AP), vegetable (VP) and yeast protein (YP) were studied for the sea urchin Heliocidaris erythrogramma (Val.). Fresh macroalga Ulva australis was used as a natural control diet. Triplicate groups of five animals were fed one of the four diets ad libitum every second day for 85 days. Sea urchins fed pelleted feeds had significantly higher food consumption rates (dry basis) and significantly lower total and protein absorption efficiencies compared with the algal diet. The gonad yield and gonad production efficiency in sea urchins fed the natural diet were significantly higher compared with initial group (gonad yield only) and urchins fed animal and vegetable diets, but did not differ significantly from those of the animals fed the yeast diet. Percent protein and lipid in the gonads were not affected by the dietary source. The taste and smell of gonads were generally better in sea urchins collected from the wild or fed yeast and natural diets than in sea urchins fed animal and vegetable diets. The animal protein diet was the most stable in seawater while the yeast protein diet had the poorest water stability. The results of this study suggest that development of a more stable, single‐cell, protein‐based diet has a potential to promote gonad production of H. erythrogramma.     

Cold Storage of Six Marine Benthic Diatoms Native to the Mexico Pacific Coast

Cultures of six benthic diatoms were maintained in the dark to measure their viability and biochemical composition after 8 wk of storage at low temperature (4 C) in darkness by refrigeration. Cell density, growth rate, and viability for each benthic diatom changed significantly after storage. Significant differences were observed with regard to cell size (length and width) of Nitzschia laevis, Navicula sp., and Amphora tenerrima as a result of storage. In general, the proximal composition of the benthic diatom cultures changed after week 1 of storage and decreased after week 4 of storage for all the diatoms. These results demonstrate that under 1–4 wk of storage these diatoms maintain their viability and had changes in their proximal composition in species‐specific responses. Storage of preserved live microalgae cells is an alternative technique that can be used to reduce the need for continuous maintenance of live cultures and can provide live feed stock for aquaculture applications.     

Formulated Feed Supports Weight Gain and Survivorship in Juvenile Sea Urchins Lytechinus variegatus

In adult sea urchins, formulated feeds can support both weight gain and gonad production; however, studies demonstrating the effects of formulated feeds on juvenile sea urchin growth are limited. In this study, juvenile sea urchins (test diameter: 3.20–7.33 mm, N = 12 per treatment) were reared individually in artificial seawater and fed with one of four experimental feeds: (1) mixed‐taxa algal biofilm (MTAB), (2) freeze‐dried MTAB, (3) a commercial, small‐mammal feed (Friskies^® cat treats), or (4) a semipurified feed formulated for sea urchins. The MTAB and sea urchin feed supported weight gain and survival throughout the study; however, those individuals fed with the sea urchin feed exhibited a short lag period at the onset of feeding. This short lag period may be, in part, because of an initial lack of attraction of the urchins to the formulated feed. Furthermore, we hypothesize that gut physiology or gut flora must acclimatize to a new diet (all sea urchins were reared initially on the MTAB diet). The freeze‐dried MTAB and mammal feed did not support substantial weight gain. This study suggests that sea urchin juveniles as small as 3–4 mm can utilize formulated feeds for growth.     

Protein and energy digestibility and gonad development of the European sea urchin Paracentrotus lividus (Lamarck) fed algal and prepared diets during spring and fall

Protein and energy are two of the main limiting factors for sea urchin growth. However, the requirement of daily protein and energy to maximize gonadal production is still unknown. Paracentrotus lividus were fed three experimental diets: Ulva lactuca, Gracilaria conferta and a prepared diet for 2 months in the fall of 1999 and spring of 2000. Sea urchins from a laboratory‐cultured population of equal age, weight and test diameter were used. Apparent digestibility coefficients (ADC%) for protein and energy, using acid‐insoluble ash as a marker, were measured for all experimental diets. Apparent digestibility coefficients for protein was high (>75%) for all diets. Energy digestibility varied among the diets and was lowest for G. conferta (50–62%). The three diets contained varying digestible protein (DP) to digestible energy (DE) ratios of 25, 26 and 12 mg kJ^?1 for U. lactuca, G. conferta and the prepared diet respectively. Digestible protein intake was similar for all treatments, but DE intake was greater for sea urchins fed the prepared diet in both seasons. As a result, the gonad production was significantly higher for urchins fed the prepared diet, suggesting that energy was limiting in the algal diets. Paracentrotus lividus spawned during the spring experiment, resulting in protein loss in all treatments. Protein loss was lowest in the sea urchins fed the prepared diet. Enhanced gonadal growth and gamete development of P. lividus resulted from the higher dietary energy content of the prepared diet.     

Agar‐based pellets as feed for sea urchins (Paracentrotus lividus): rheological behaviour,digestive enzymes and gonad growth

The algal polysaccharide agar has long been used as a food binder due to its structure, rheological behaviour, stability and interactions – properties that help to generate firm, round, disk‐shaped pellets that may be used in recirculating sea urchin‐rearing systems. Three algae‐based diets (Ulva lactuca, Gracilaria gracilis, Cystoseira sp.) containing 3% and 6% agar were tested on the sea urchin Paracentrotus lividus in order to examine the effect of varying percentages of agar on pellet stability in water and sea urchin gonad growth. The kinetics of water absorption and solute leaching of pellets were measured by immersing quadruplicate samples of the pellets in water for 1, 2, 3, 4, 5 and 6 days. Our results show that the pellets had good water stability, were readily consumed by sea urchins and the presence of agar did not hamper sea urchin gonad growth. Animals fed Ulva‐containing pellets reached a more advanced gametogenic stage with respect to animals fed Cystoseira‐ and Gracilaria‐containing pellets. Moreover, the presence of agarase activity in the digestive system indicated that agar may be an energy source. Pellets are relatively low cost and easy to prepare and store. They may represent a useful resource for rearing sea urchins under intensive conditions.     

Feasibility of Offshore Co‐culture of Abalone,Haliotis discus hannai Ino,and Sea Cucumber,Apostichopus japonicus,in a Temperate Zone

Feasibility of offshore co‐culture of abalone and sea cucumber was investigated in Northern China. Survival and growth of abalone, Haliotis discus hannai Ino, and sea cucumber, Apostichopus japonicus, co‐cultured in abalone cages from suspended longlines, in the offshore area, were examined. Abalone and sea cucumbers were co‐cultured at density ratios of both 3:1 and 6:1 for 1 yr. Abalone were fed with fresh kelp and no additional feed was given to sea cucumbers. Survival of abalone and sea cucumber was 100% for all treatments. Abalone and sea cucumber grew well; the body weight (BW) of abalone and sea cucumber was nearly doubled and had reached a commercial size. There were no significant differences in the growth rates for both abalone and sea cucumber between the two density treatments. The specific growth rate of BW of abalone (SGRbw) was highest in June, with a value of 0.536%/d. Growth rate of sea cucumber (SGRsc) was highest in December, reached 1.84%/d, with an annual average SGRsc of 0.182%/d. Results suggested that the offshore co‐culture of abalone and sea cucumber was feasible offshore. The co‐culture of abalone with sea cucumbers may provide an additional valuable crop without additional financial input.     

An experimental assessment on the effects of photoperiod treatments on the somatic and gonadal growth of the juvenile European purple sea urchin Paracentrotus lividus

Determining the optimum light conditions for sea urchins reared in land‐based systems is vital for the future use and assessment of possible commercial systems of sea urchin farming. The effects of two different light regimes, complete darkness and a long day photoperiod of 16 h light:8 h darkness, on the somatic and gonadal growth of the European sea urchin Paracentrotus lividus (19.5–23.0 mm) was investigated using the commercial UrchinPlatter^? System over a 6‐month period (5 March to 5 September). Hatchery‐produced P. lividus were transported to the Aquaculture Fisheries Development Centre (AFDC, University College, Cork UCC). Before arrival at the AFDC, sea urchins were reared on a diet of Laminaria digitata. Females were the predominant species of the animal group, displaying a reproductive Stage III (growing stage) where gametogenesis was commencing. Results show that darkness supports higher somatic growth than the photoperiod treatment. Feeding rates were higher for sea urchins reared under darkness with gonadal growth increasing for both experimental treatments. Individuals reared under darkness had a higher per cent change in gonad index from the initial sample taken at the beginning of the experiment.