Gonad Yield Research Articles

Heterosis of the interspecific sea urchin hybrids between Strongylocentrotus intermedius and Heliocidaris crassispina

In order to study the heterosis of the interspecific hybrids between sea urchin Strongylocentrotus intermedius and Heliocidaris crassispina, comparative culturing experiments were conducted on individuals of the same age from four groups: S. intermedius (SI), H. crassispina (HC), S. intermedius ♀ × H. crassispina ♂ (SH), and H. crassispina ♀ × S. intermedius ♂ (HS). Growth rate at different stages of development, gonadal production and quality, high-temperature tolerance, and resistance to black-mouth disease were compared among these four species. The results were as follows: in the juvenile sea urchin stage, SH sea urchins exhibited 79.11% and 55.28% body weight heterosis at 16 and 20 °C, respectively, with particularly high single-parent heterosis observed at 16 °C compared to the male parent HC (247.79%). In the young sea urchin stage, SH sea urchins displayed mid-parent heterosis in body weight at all temperatures except 28 °C, reaching a maximum of 94.62% at 12 °C. HS Sea urchins showed mid-parent heterosis only at 12, 24, and 28 °C, with the highest observed at 28 °C (36.51%). The body weight specific growth rate of SH sea urchins was significantly higher than those of the other three species (P < 0.05), and they achieved the largest body weight (48.43 g) by the end of the experiment. The gonad wet weight of SH sea urchins was significantly higher than those of the other three species (P < 0.05). While there was no difference in gonad index between SH and SI sea urchins, it was significantly higher than those of HC and HS sea urchins. In terms of high-temperature tolerance, the upper thermal tolerances (UTT) of HC and HS sea urchins were significantly higher than those of SI and SH sea urchins (P < 0.05). Regarding resistance to black-mouth disease, there was no statistically significant difference in survival rates between SH sea urchins and SI sea urchins after infection with Vibrio echinoideorum at a concentration of 1 cfu/mL. However, the survival rate of HS sea urchins was significantly higher than that of SI. The study demonstrated that the SH hybrid sea urchins exhibit notable advantages in growth and gonad yield compared to its parental species, suggesting its potential as a valuable candidate for the cultivation of new sea urchin varieties in aquaculture. These findings hold significant promise for enhancing the efficiency and sustainability of sea urchin farming practices.

Effects of Supplementary Kelp Feeding on the Growth, Gonad Yield, and Nutritional and Organoleptic Quality of Subadult Sea Urchin (Strongylocentrotus intermedius) with Soya Lecithin Intake History.

A 23-week feeding experiment was conducted to investigate the effects of supplementary kelp feeding on the growth, gonad development, and nutritional and sensory properties of sea urchin (Strongylocentrotus intermedius) with soya lecithin (SL) intake history. The feeding experiment was divided into experimental phase I and phase II. During phase I, 48 subadult sea urchins (initial weight: 6.28 ± 0.07 g) were fed one of the feeds with different levels of SL (0%, 1.6%, 3.2%) or kelp (Saccharina japonica) for 12 weeks. Then, all sea urchins were fed kelp for the next 11 weeks during the phase II. Each diet was randomly allocated to six cages of sea urchins. The results of phase I showed that weight gain rate (WGR), gonadosomatic index (GSI), gonad sensory properties (color and texture), and essential amino acid (EAA) contents were not significantly affected by SL level in the feed groups. High level (3.2%) of SL suppressed gonad development of S. intermedius with retarded gametogenesis in the 3.2% SL group (stage Ⅱ) compared to those fed 0% and 1.6% SL groups (stage Ⅲ). Sea urchins fed dry feeds exhibited significantly lower WGR and values of color (redness and yellowness) and texture (hardness and gumminess) but higher contents of EAA in the gonads than those fed kelp. The n-3/n-6 polyunsaturated fatty acid (PUFA) and eicosapentaenoic acid (EPA) of gonads in the groups fed with dry feeds showed no significant differences, but were significantly lower than that of kelp group. At the end of phase II, the gonad yellowness and EPA content of gonads in all dry feed groups were significantly increased by supplementary kelp feeding, with a higher increase observed in S. intermedius with SL intake history, while arachidonic acid (ARA) content was significantly improved by supplementary kelp feeding in S. intermedius with SL intake history. Gonad texture was improved to some extent by supplementary kelp feeding. These results indicated that S. intermedius fed dry feeds showed significantly higher GSI and EAA but poorer organoleptic quality and lower n-3/n-6 PUFA and EPA than those fed kelp. Kelp supplementary feeding improved the fatty acid value and organoleptic quality of gonads, especially for the sea urchins with SL intake history.

Turning waste into gold: Sustainable feed made of discards from the food industries promotes gonad development and colouration in the commercial sea urchin Paracentrotus lividus (Lamarck, 1816)

Development of sustainable aquaculture practices is a suitable solution to reduce the pressure on overexploited stocks of the Mediterranean sea urchin, Paracentrotus lividus, and to respond to the increasing market demand. To move forward the Blue Growth and following the principles of circular economy, a three-month feeding experiment was conducted to test a sustainable feed based on food processing discards on sea urchins. Two feed formulations differing on the proportions of the two main ingredients (endive outermost leaves and European anchovy discards in a ratio of 60:40 and 80:20 respectively) were prepared and tested on P. lividus gonad yield, development and quality. The results were compared with those of wild sea urchins to assess the differences with natural patterns. Both feed formulations promoted gonad growth resulting in a significantly higher percentage increase in gonad biomass compared with wild specimens (490%, 330% and 78% increase in gonad weight in the feed 60/40, 80/20 and wild sea urchins respectively). Similarly, GSI of reared sea urchins varied by about 3–12% and 14% for sea urchins fed with feeds 80/20 and 60/40 respectively, while that found in wild sea urchins varied by about 3–5%. Gonad development was also boosted by the provision of the sustainable feed, as sexual maturation was faster in reared specimens than in wild ones. At the end of the trial, reared sea urchins showed also a very high (> 90%) frequency of marketable gonad colour. Lastly, the formulation with a more balanced vegetal/animal ratio (feed 60/40) gave the best results overall, combining the highest GSI and the best gonad colouration. Outcomes of this study confirm the suitability of food processing discards as ingredients for sea urchin feeds, although further research is needed to evaluate the effects on nutritional quality and organoleptic features of sea urchin gonads.

Segregation in multi-layer culture avoids precocious puberty, improves thermal tolerance and decreases disease transmission in the juvenile sea urchin Strongylocentrotus intermedius: a new approach to longline culture

Mass mortality of commercially cultured marine species in summer is the most serious problem for the longline culture. Reducing crowding stress induced by high stocking density on the basis of high biomass is proposed to be an important approach to solving this issue.A laboratory experiment with multi-layer culture (18 sea urchins total, 6 urchins in each layer) was conducted to investigate gonad yield, gonadal development, thermal tolerance (CTmax) and disease transmission for the juvenile sea urchins Strongylocentrotus intermedius for ~7 weeks at elevated temperatures. The present study found that precocious puberty occurred both in those sea urchins cultured in multi-layer and those not (control group), indicating that gonadal development is accelerated by crowding stress (even in a low density of 6 sea urchins/1834.56 cm3). The CTmax showed a significantly negative correlation with gonadal development, suggesting precocious puberty probably is responsible for the decrease of resistance ability.We further assessed whether segregation in multi-layer culture improves these important traits of sea urchins. This approach significantly reduced gonadal development, improved CTmax and lower mortality and morbidity after disease challenge assays in sea urchins than those not separated in multi-layer culture, which efficiently reduces the gametogenesis, improves resistance ability and decreases disease transmission. The present study establishes a new approach to improving the survival of cultured organisms in the longline culture at high temperatures.

Growth performance and gonad yield of sea urchin Paracentrotus lividus (Lamarck, 1816) fed with diets of increasing protein: energy ratios

The establishment of a commercially sustainable aquaculture production of Paracentrotus lividus depends on the development of diets able to fulfil the species nutritional requirement and the production of market valuable roe. As dietary protein level and protein: energy ratio (P:E) are major limiting factors for sea urchin growth and gonad development, six isolipidic (≈ 7%) practical diets of increasing protein content (20, 25, 30, 35, 40 and 46 % dry matter, DM) and protein: energy ratios (P:E) (15, 18, 21, 24, 27 and 28 mg P/kJ) were fed to triplicate groups of adult sea urchins for 107 days to identify the dietary protein level and P:E able to promote the highest nutrient utilisation, best growth and gonad enhancement. The trial results showed that protein apparent digestibility coefficients ranged between 69 and 86 %, without significant differences among groups. Digestible energy intake and feed conversion ratio (FCR) decreased with increasing dietary protein levels and protein: energy ratios, whilst digestible protein intake remained similar in all groups. The retention and gain of protein and energy remained unaffected by dietary treatments, resulting in a specific growth rate of 0.3 % per day across treatments, and in a final body weight between 22 and 24 g. All diets significantly increased the gonadosomatic index (GSI) attaining 7.4–8.5%. Both GSI and gonad protein gain picked with a dietary P:E of 21 mg P/kJ (diet P30), whereas gonad protein content picked when P:E was 24 mg P/kJ (diet P35). These results, in association with the decreasing FCR with increasing dietary protein levels, suggest that diets with 30 % DM of protein and a P:E of 21 mg P/kJ are the most appropriate to promote both high somatic growth and high gonad yield in adult P. lividus.

Effect of Transport Method on Subsequent Survivorship and Gonad Yield/Quality in the Red Sea Urchin Mesocentrotus franciscanus

AbstractSea urchin gonad enhancement entails collecting adults with low gonad yields from the wild, placing them in land‐based or sea‐based captivity, and feeding them a prepared or natural diet to produce high quality/quantity gonads for marketing. Collection and transportation to the culture facility can be stressful to the urchins and cause subsequent mortalities and suboptimal gonad yield/quality. Minimizing this handling stress is critical to ensuring maximum survivorship and optimal gonad enhancement, yet very little research has examined this, with no information being available for the red sea urchin Mesocentrotus franciscanus. The present study examined survivorship, gonad yield, and gonad quality of red sea urchins 2 weeks after exposure to three 2‐h transport methods: (1) milk crates placed in two plastic fish totes filled with ambient seawater (“wet crate”), (2) sealed Styrofoam boxes filled with ambient seawater (“wet box”), and (3) sealed Styrofoam boxes without seawater, but with wet burlap placed on top of the urchins (“dry box”). While no gonadal parameters significantly differed between transportation methods, the percentage of survivorship for both the wet boxes and wet crates was 100%, while that for the dry boxes was 58.3% after 2 weeks, indicating that wet transport should be preferred over dry transport for red sea urchins.

Effects of macroalgae Gracilaria lemaneiformis and Saccharina japonica on growth and gonadal development of the sea urchin Strongylocentrotus intermedius: New insights into the aquaculture management in southern China

Taking advantage of the seasonally appropriate water temperature in southern China is an important approach to expanding Strongylocentrotus intermedius aquaculture for the increasing market demand. However, appropriate diets remain largely uninvestigated and seed supply is in shortage, leaving the most serious problems of S. intermedius aquaculture in southern China unaddressed. Here, a feeding experiment was conducted for ∼6 months (from November 2018 to May 2019) to compare the somatic and gonadal growth, as well as gonadal development of S. intermedius (∼30 mm of test diameter) fed either macroalgae Gracilaria lemaneiformis or Saccharina japonica at the temperatures simulating water those off southern China coast (Fuzhou, 119°50′ E, 26°24′ N). Test size, wet body weight, specific growth rate, lantern size, wet gut weight and gonad yield of S. intermedius fed S. japonica were all significantly larger than those of sea urchins fed G. lemaneiformis. The present results indicate that long-term feeding G. lemaneiformis is unacceptable for aquacultural S. intermedius in southern China, because of the inefficiency of supporting somatic and gonadal growth. Saccharina japonica may suffice as a suitable diet for the aquaculture of S. intermedius in southern China. Further, spent gonads were observed in S. intermedius fed G. lemaneiformis in May 2019, meanwhile all gonads of individuals fed S. japonica remained in the premature stage. This suggests that G. lemaneiformis displays a promising potential for accelerating gonadal development of S. intermedius and subsequently supports the seed production of sea urchins in spring in southern China. The present study provides valuable information into the aquaculture management of S. intermedius in southern China.

Aquaculture of green sea urchin in the Barents Sea: a brief review of Russian studies

AbstractGonads of the green sea urchin (Strongylocentrotus droebachiensis) containing valuable carotenoids, polyunsaturated fatty acids, phospholipids and sulphated fucans are in great demand from the expanding market. In Russian waters of the Barents Sea, only a few sites are suitable for commercial harvesting and thus the development of green sea urchin farming in this region. Our review presents a short survey of Russian literature on biological aspects and rearing methods of green sea urchins in the Barents Sea. In the 1980s, spawning induction and larval culture experiments were undertaken to obtain larvae of S. droebachiensis. Later studies were undertaken to test optimal rations and conditions for gonad enhancement of adult sea urchins in sea cages and closed systems. Gonadal growth was higher and faster in sea urchins reared under controlled conditions in closed water circulation tanks compared with sea cages. Regular feeding of cultured animals provided them better gonadal growth than in wild sea urchins irrespective of food items. Algal diets showed a lower level of gonad yield compared with mixed diets (algae + squid, algae + fish), fish diets and prepared diets (artificial feed based on fish skin). The coast of the Kola Peninsula has a good potential for the development of the green sea urchin farming but several financial, socio‐economic, logistic and management problems must be solved before this process starts.

Effect of protein and lipid levels in diets for adult sea urchin Paracentrotus lividus (Lamarck, 1816)

Paracentrotus lividus gonads are considered a prized seafood delicacy due to its organoleptic features. The increasing market demand for sea urchin depleted several wild stocks, thus aquaculture can play an important role in supplying high-quality animals. Nevertheless, the success of this activity largely depends on the development of nutritionally balanced diets capable of producing excellent gonads. In this study, four extruded diets formulated with low or high protein (30 and 50% dry matter (DM), LP and HP, respectively) and lipid (6 and 11% DM, LL and HL, respectively) levels were fed to wild-caught individuals (4.5 cm diameter) for 15 weeks. Twelve homogeneous groups of 15 individuals were randomly distributed by mesh cages (45 urchins/m2) within 250 L tanks in a recirculating aquaculture system (RAS) at 18 °C and a 12 L:12 D photoperiod regime. Sea urchins fed the LP/LL diet were compared to wild specimens with similar maturation stage.All experimental diets were well accepted by sea urchins and resulted in similar final body weight (42–43 g). No significant differences were observed in specific growth rate or protein efficiency ratio among diets. The HP diets led to a decrease of dry matter and energy intake resulting in the lowest feed conversion ratio (FCR). Weight gain, whole body composition and nutrient gain remained similar among dietary treatments. The gonad somatic index (GSI) varied between sex but was similar among dietary treatments (19–23%) and was higher than values observed in wild specimens (6–7%). Females had significantly higher total concentration of carotenoids than males, irrespectively of the dietary treatments. Dietary treatments and sex did not affect gonad texture (firmness and resilience) or colour parameters (brightness, redness, yellowness, chroma or hue angle), but affected gonad composition. Total carotenoid content in gonads was not affected by diets and resulted in lower values compared to wild specimens. These had higher levels of echinenone, β-cryptoxantin and β-carotene and showed higher redness and firmness values when compared to the LP/LL diet, irrespectively of the sex. Gonad lipid content and n-3 PUFA were higher in female than in male, whilst protein content showed an opposite trend, suggesting some sex related differences in the metabolic use of nutrients.This study clearly shows that it is possible to enhance sea urchin gonad yield in relation to wild animals in a RAS at 18 °C. All diets were effective in promoting gonad growth, but the diet with the lowest protein (30% DM) and lowest lipid (6% DM) level resulted in the highest gonad yield in both sexes.

The effect of sex, season and gametogenic cycle on gonad yield, biochemical composition and quality traits of Paracentrotus lividus along the North Atlantic coast of Portugal

Sea urchin population harvest in the North Atlantic coast of Portugal was characterized in terms of gonad yield, nutritional composition and important market-related traits, over one reproductive cycle (March 2016 to March 2017). Most of the quality attributes showed a seasonal variation strongly dependent on sea urchin sex. Maximum gonad yield (18%) was observed in March 2017. A single spawning event occurred between May and July. Gonads are rich sources of protein (12–18% WW) with low fat content (≤6% WW), that increase during the gametogenic stages of recovery and growing (November-December). Polyunsaturated fatty acids were the dominant class in both sexes (4.2–14.7 mg.g−1 WW), being preferentially accumulated in females. Total gonads carotenoid varied seasonally, with the highest level being observed in males during spawning season. Echinenone was the main pigment present in gonads, showing highest concentrations in males during spawning and gonad recovering. During the growing and early maturation period gonads were more reddish, yellowish and brighter, as well as more firm, irrespectively of the sex. Based on all seasonal changes affecting gonad yield and quality, the period between November and February seems the most suitable to harvest high quality gonads in the Atlantic coast of Portugal.

Ulva lactuca biofilter from a land-based integrated multi trophic aquaculture (IMTA) system as a sole food source for the tropical sea urchin Tripneustes gratilla elatensis

The performance of Tripneustes gratilla elatensis using IMTA-produced Ulva lactuca as the sole food source, in comparison to Gracilaria conferta and formulated diets, was evaluated in a long term (251-day) experiment in a land based facility in the tropical Gulf of Aqaba. T. gratilla elatensis fed IMTA-produced U. lactuca exhibited significantly (P < 0.01) better performance in terms of somatic growth, SGR, gonad yield, colour and survival, compared to sea urchins fed G. conferta and formulated diets. These differences can be attributed mainly to the high consumption rate and digestibility of the protein rich Ulva compared to the other diets. IMTA-produced Ulva as a sole feed was found to be a suitable diet for both somatic and gonadal growth. T. gratilla elatensis was shown as able to reach a commercial test size (~60 mm) in 5–6 months. T. gratilla elatensis grew (from spawning) in 400 days to 44.44 ± 2.01, 61.80 ± 3.69, and 73.28 ± 1.46 mm test diameter with average Specific Growth Rate (SGR) of 0.21 ± 0.02, 0.35 ± 0.05, and 0.42 ± 0.03% d−1 for formulated diet, G. conferta and U. lactuca diets, respectively. Gonad weights were 9.14 ± 2.3, 8.5 ± 2.7 g, and 24.6 ± 7.4 g. and Gonado-Somatic Index (GSI) reached 14.4 ± 2.01, 13.1 ± 5.0, and 13.7 ± 4.56 for formulated diet, G. conferta and U. lactuca diets, respectively, at the end of the experiment. No specific seasonality was observed with regard to gonad development, growth and GSI dynamics. Gonad growth and spawning events occurred throughout the year. T. gratilla elatensis fed IMTA-produced Ulva exhibited 90–100% commercially acceptable gonad colour, while the formulated diet (10% Ulva inclusion) showed poorer results of 30–60% acceptable colour and the G. conferta diet ca. 80%. In addition to enhancing sea urchin performance, U. lactuca as a biofilter in the IMTA considerably improved the system's sustainability and waste management.

Influence of a prepared diet and a macroalga (Ulva sp.) on the growth, nutritional and sensory qualities of gonads of the sea urchin Paracentrotus lividus

This study evaluated the growth of the purple sea urchin Paracentrotus lividus, fed with two diets, in sea- and land-based systems compared to wild populations. The experiments investigated the effects of the feeding regimes on gonad yield, nutritional traits and overall quality. Sea-based trials were performed by the CNR of Taranto (Trial S), whereas land-based trials were performed in the facilities of the University of Cagliari (Trial L). Urchins fed with a laboratory prepared pelletized diet (P), and a mix diet PU (50% of P-Diet and 50% of fresh Ulva sp.) were compared to wild urchins (W). In both trials the experimental diets supported a gonad growth when compared to wild population (p < .05). Sensory characteristics, assessed by 6 panel experts for each trial, highlighted significant differences in gonad colour and taste in both trials, while only in Trial S for texture (p < .05). The changes in the biochemical composition of sea urchins' gonads caused significant variations in the nutritional profile. Sea urchins fed with the experimental diets contained higher levels of total protein and lipids and PUFAs than wild sea urchins, although EPA, DHA and n-3/n-6 ratio, were lower in urchins fed with artificial diets. In Trial L, total free amino acids showed an increase respect to W gonads (p < .05), whereas in Trial S, total free amino acids showed a decrease only in sea urchin fed with P-Diet (p < .05). The results presented in this study provide evidence of the good performance of the formulated diet assuming its application for the development of Mediterranean echinoculture.

Exploring benefits of spatial cooperative harvesting in a sea urchin fishery: an agent‐based approach

AbstractSedentary or low‐mobility organisms show a high degree of dependency with their substrate, where its heterogeneity often determines small‐scale spatial patterns of distribution, life history traits, and fishery yields. For sea urchins, this spatial structure is usually shaped by food availability, habitat structure, individual movement, and fishery dynamics. All of these have a significant impact on their physiological and reproductive status and in particular on their gonadal content. These patterns are of particular interest considering that the sea urchin fishery is a roe fishery where marketability depends on gonad yield and quality, which in turn is related to spatial and temporal variations in associated kelp beds. Thus, better gonad quality and yields generate higher profits for both fishers (divers) and processors. However, competition among divers within a non‐cooperative system creates a “race for shellfish” precluding higher gonad yields per unit of effort. A spatially explicit agent‐based model for the San Diego, California red sea urchin (Strongylocentrotus franciscanus) fishery was developed in order to assess the benefits of cooperative harvesting by depicting spatial and temporal variations in fishery yields. A cooperative harvesting scenario where divers consistently target those areas with higher yields avoiding low‐quality sea urchins was compared against a non‐cooperative situation where divers harvest at random or based only on densities of sea urchins. Sea urchin population at the end of the simulation period was 20% higher for the most cooperative scenario compared to the non‐cooperative fishery. Further, for the most cooperative scenario where information sharing among divers is greatest and harvest is coordinated, sea urchin catches were at least 10% higher and gonad yield 35% higher than in the non‐cooperative scenario. In this model, information sharing and organized harvesting typical of well‐functioning cooperatives allowed fishers to optimize the use of the resource in terms of higher gonad yields per unit of effort while maintaining the productivity of the stock. This study also highlights the importance of community‐based management (i.e., collaborative efforts in assessment, management, and governance of fisheries between fishers, scientists, and managers) toward improving fisheries sustainability.

Ingestion, Absorption and Assimilation Efficiencies, and Production in the Sea UrchinArbacia dufresniiFed a Formulated Feed

Fil: Rubilar Panasiuk, Cynthia Tamara. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - Centro Nacional Patagonico. Centro para el Estudio de Sistemas Marinos; Argentina

Long-term effects of stocking density on survival, growth performance and marketable production of the sea urchin Strongylocentrotus intermedius

Sea urchins were stocked at a density of 15 (D15), 30 (D30), 45 (D45) and 60 (D60) urchins/cage (0.3 m long × 0.2 m wide × 0.4 m high) in a laboratory culture environment for 16 months. The wet body weight (BW) and test diameter growth were monitored at 2-month intervals during the experiment. At the conclusion of the experiment, the surviving sea urchins were counted and the gonad wet weight (GW) and gonad color were measured. Specific growth rate (SGR) of body weight, survival rate (SR), gonad index (GI), gonad color difference (ΔE00), coefficients of variation (CV) of BW, GW, GI and ΔE00, total biomass yield (TY) and total gonad yield (TGY) per cage were calculated. Two marketable yield variables, graded according to gonad index, i.e., marketable biomass yield (MY) and marketable gonad yield (MGY), were also calculated. Coefficient of variation of final body weight (FW) and final test diameter (FTD) of sea urchins increased as the stocking density increased, indicating the existence of adverse social interactions. These adverse social interactions detrimentally affected FW, FTD, SGR, GW and GI (P < 0.01). Although SR decreased with the increasing densities, no statistical significant difference was detected. Sea urchins at D15 had the lowest gonad color difference (ΔE00) (P < 0.05). However, statistically equal CV of ΔE00 indicates this density effect was not a result of adverse social interactions. TY and TGY increased with increased density and can be described by the following equations: TY = 84.18X0.64, R2 = 0.999 and TGY = 24.16X0.38, R2 = 0.979. However, the MY and MGY were not significantly different among stocking densities. The results of this study demonstrate that in intensive culture S. intermedius at low stocking density can achieve high growth rate, gonad index and desirable color without decreasing the marketable yield. Farmers should choose to culture S. intermedius at low stocking densities.

Çeşme Körfezi'ndeki (Doğu Ege Denizi) Avrupa Deniz kestanesinin (Paracentrotus lividus, Lamarck, 1816) gonad ve mide indeksleri

The objective of present study is to determine the gut and gonad yield of Paracentrotus lividus populations occuring along Aegean Sea coastline and to evaluate of the environmental conditions on the gonad indices variability. To achieve this, samples were gathered during twelve months and biometric measurements were done. The wet gonad index peaked (6.22±0.56 %) in one (April-14°C) of the coldest months (between November-May) even though water temperature was not change so much between November and May. It is determined that decreasing temperature affected gonad production but temperature is not only one factor effecting of gonad because of gonad indices were not high during the other cold months (between November-May) in this study. The higher gut index (GII) values were observed between January (6.31±0.71 %) and May (6.07±0.70 %). The gut index was higher in spring than in fall in this study.

Use of fresh vegetable discards as sea urchin diet: effect on gonad index and quality

This study evaluated the exploitation of unprocessed agricultural discards in the form of fresh vegetable leaves as a diet for the sea urchin Paracentrotus lividus through the assessment of their effects on gonad yield and quality. A stock of wild-caught P. lividus was fed on discarded leaves from three different species (Beta vulgaris, Brassica oleracea, and Lactuca sativa) and the macroalga Ulva lactuca for 3 months under controlled conditions. At the beginning and end of the experiment, total and gonad weight were measured, while gonad and diet total carbon (C%), nitrogen (N%), δ13C, δ15N, carbohydrates, lipids, and proteins were analyzed. The results showed that agricultural discards provided for the maintenance of gonad index and nutritional value (carbohydrate, lipid, and protein content) of initial specimens. L. sativa also improved gonadic color. The results of this study suggest that fresh vegetable discards may be successfully used in the preparation of more balanced diets for sea urchin aquaculture. The use of agricultural discards in prepared diets offers a number of advantages, including an abundant resource, the recycling of discards into new organic matter, and reduced pressure on marine organisms (i.e., macroalgae) in the production of food for cultured organisms.

Banana peel provides a new insight into improving gonad flavor in the sea urchin Strongylocentrotus intermedius

To our knowledge, little information is available on approaches to improving gonad flavor of sea urchins. Although sea urchins fed high content of glutamate and glycine perceived sweeter gonads than those fed high content of valine and methionine (Phillips et al. in Aquaculture 288:205–215, 2009), the problem of improving gonad quality has not been completely solved. Because of the high cost of glutamate and glycine, it is hard to move this finding from the laboratory to gonad production. In the present study, we found that gonad flavor of Strongylocentrotus intermedius fed banana peel was significantly better than that of individuals fed kelp or pumpkin (P < 0.001). However, banana peel did not significantly support gonad yield of sea urchins compared with kelp (P < 0.05). This novel finding provides a new insight into the gonad quality improvement in sea urchins. Further studies should be carried out to test our two suggested methods of banana peel application in sea urchin aquaculture.

Feeding preference and performance in the tropical sea urchin Tripneustes gratilla

Sea urchin aquaculture has two sequential steps relating to performance, optimising somatic growth followed by conditioning of the gonad (roe) as the end product. Quantifying dietary preferences and consumption on performance is a first step in maximising somatic growth and subsequently optimising gonad conditioning. In this study we evaluate dietary preferences, consumption, and performance in the tropical sea urchin, Tripneustes gratilla across a broad range (29 species) of algae. T. gratilla has strong and consistent preferences for algal species, however, there was less discrimination among brown algae compared to red and green algae. The outcomes of preference (choice) experiments were generally reflected by consumption rates (g.hr−1) in no choice experiments. Performance experiments with four clearly preferred and abundant species, Sargassum flavicans and Cystoseira trinodis (brown algae), Hypnea pannosa, and Laurencia intricata (red algae), and a mixed diet of all species, provided contrasting outcomes. Brown algae, and the mixed diet, provided the highest growth rates and gonad yields. Red algal diets provided poor growth performance as single species diets, but improved holistic performance in terms of growth, test diameter and gonad yield, when combined with brown algae in a mixed species diet.

Effects of three feeding models on growth,gonad yield and gonad quality of the sea urchin(Strongylocentrotus intermedius)

Effects of three feeding models on growth rates throughout the whole growth cycle,gonad yield and gonad quality at harvest of the sea urchin Strongylocentrotus intermedius were studied.Six-month-old sea urchins were selected and fed on three diets kelp(E1),kelp+mussel(E2),maize+mussel(E3)to harvest.The test diameter and live body weight of sea urchins were measured every two months.The gonad weight,gonad moisture content and gonad color were measured at the end of the experiment.Results showed that:the feeding model significantly affected(P0.01)the test diameter and live body weight of the sea urchin during its growth stage.The test diameter and live body weight performed as:E2E1E3 among feeding models.The feeding model significantly affected most specific growth rates(SGRs)of the test diameter and live body weight(P0.01),which ranked as:E2≥E1E3.The feeding model significantly affected the gonad yield and gonad quality at harvest(P0.05 or P0.01).E2[female:(7.58±1.21)g,male:(7.74±1.95)g]was the optimal model for the gonad wet weight,followed by E1 [female:(4.50±1.20)g,male:(4.87±1.02)g].E3[female:(2.66±1.02)g,male:(2.32±0.75)g]was the worst model.E2(female:15.07%±1.84%,male:15.83%±3.01%)was the optimal model for the gonad index,followed by E1(female:11.54%±4.94%,male:11.84%±3.70%)and E2(female:12.48%±4.33%,male:12.78%±3.73%).E2 and E1 were the optimal models for the gonad moisture content and gonad color,while E3 was the weakest.Effects of the feeding model on male or female sea urchins were similar.The result suggested that,S.intermedius can grow good test diameter by feeding kelp only.Animal protein can significantly improve the growth rate and gonadal production of S.intermedius.Kelp+mussel model can be applied to improve the culture efficiency of the sea urchin.Maize had no beneficial effect on the promotion of the growth,gonad yield and quality of the sea urchin.Even if animal protein was added,maize+mussel can hardly be an alternative feeding model in aquaculture of S.intermedius.