Culture of Juvenile Atlantic Surfclams, Spisula solidissima solidissima and Spisula solidissima similis, in Forced-Flow Upwellers in a Bivalve Hatchery in Coastal Georgia

Four experimental growth studies for juvenile Atlantic surfclams, Spisula solidissima solidissima and Spisula solidissima similis , under hatchery conditions were conducted in 10-cm diameter forced-flow upweller units. Experiments were designed to determine optimum food ration (2%, 5%, and 8% g dry weight of algae/g wet weight of clam), water culture temperature (20, 25, and 30°C), flow rate (2, 4, and 6 Lpm), and stocking density (7, 14, and 21 g wet weight of clams) for rearing juvenile clams in upweller units. Each experimental trial was performed for a 14-d period. Nested Analysis of Variance showed that juvenile surfclams Spisula solidissima similis grew significantly faster at a temperature of 20°C and food rations of 5 % and 8%. In all four experiments, clam mortalities were not observed except in the temperature experiment, where total mortality occurred for clams cultured at 30°C. Clam growth in biomass and size decreased significantly with increases in culture temperature. For Spisula solidissima solidissima , clam growth was significantly reduced in terms of size and biomass at a flow rate of 6 Lpm. No difference in size or biomass was determined between clams grown at a flow rate of 2 or 4 Lpm. Surfclams at the lowest stocking density of 7 g wet weight significantly increased more in net biomass compared to those at higher stocking densities. Clams were significantly larger in shell length when grown at the two lower stocking densities compared to those at the highest stocking density. Hatchery-rearing protocol for juvenile surfclams is discussed.     

Comparative Gametogenesis of Spisula solidissima solidissima and Spisula solidissima similis Cultured in Coastal Georgia

Abstract— The reproductive cycle of two subspecies of surfclams, Spisula solidissimu solidissima and Spisulu solidissimu similis , cultured under similar nursery and field conditions were examined. Monthly gonadal examination showed that S. s. similis initiated gametogenesis, achieved mature status, and spawned earlier than S. s. solidissimu. S. s. similis spawned from January to June, while S. s. solidissimu spawned in May. S. s. similis exhibited an equal sex ratio; whereas, S. s. solidissima had significantly more males than females (1.00 M: 0.32 F). Implications for aquaculture development of surfclams are discussed.     

Combined Effects of Turbulence and Salinity on Growth, Survival, and Whole-body Osmolality of Larval Southern Flounder

The southern flounder (Paralichthys lethostigma) is a commercially important marine flatfish from the southeastern Atlantic and Gulf Coasts of the USA and an attractive candidate for aquaculture. Hatchery methods are relatively well developed for southern flounder; however, knowledge of the optimum environmental conditions for culturing the larval stages is needed to make these technologies more cost effective. The objectives of this study were to determine the effects of water turbulence (as controlled by varying rates of diffused aeration) on growth, survival, and whole‐body osmolality of larval southern flounder from hatching through day 16 posthatching (d16ph). Embryos were stocked into black 15‐L cylindrical tanks under four turbulence levels (20, 90, 170, and 250 mL/min of diffused aeration) and two salinities (24 and 35 ppt) in a 4 × 2 factorial design. Larvae were provided with enriched s‐type rotifers from d2ph at a density of 10 individuals/mL. Temperature was 19 C, light intensity was 390 lx, and photoperiod was 18 L:6 D. Significant (P < 0.05) effects of turbulence on growth (notochord length [NL], wet weight, and dry weight) were observed. On d16ph, NL (μm) increased with decreasing turbulence level and was significantly greater at 20 mL/min (64.2) and 90 mL/min (58.2) than at 170 mL/min (56.3) and 250 mL/min (57.2). Survival declined primarily during the prefeeding and first‐feeding stages from d0 to d8ph, then stabilized from d8 to d16ph. In contrast to growth trends, survival (%) on d16ph increased with increasing turbulence levels and was significantly greater at 170 mL/min (57.9) and 250 mL/min (54.0) than at 20 and 90 mL/min (21.4 and 26.2, respectively). Mean rotifer concentrations (individuals/mL) at 24 h postfeeding were significantly higher (P < 0.05) in the low‐turbulence treatments of 20 mL/min (4.48) and 90 mL/min (4.23) than in the high‐turbulence treatments of 170 and 250 mL/min (2.28 and 2.45, respectively). Under both salinities, larval whole‐body osmolality (mOsm/kg) increased with increasing turbulence levels and was significantly higher at 250 mL/min (427) than at 20 mL/min (381), indicating osmoregulatory stress at the higher turbulence levels. On d14ph, larvae in all treatments were positively buoyant in 35 ppt and negatively buoyant in 24 ppt. Results showed that growth of southern flounder larvae in 15‐L tanks was maximized under low turbulence levels of 20 and 90 mL/min, while survival was maximized at high turbulence levels of 170 and 250 mL/min. The data suggested that, in prefeeding‐ and early‐feeding‐stage larvae (which have weak swimming ability), higher turbulence levels improved buoyancy and prevented sinking. In feeding‐stage larvae (which are relatively strong swimmers), higher turbulence levels caused excessive swimming, osmoregulatory stress, and slower growth. Based on these results, we recommend that turbulence levels be maintained relatively high during prefeeding (yolk sac) and first‐feeding stages to maintain buoyancy and survival and then decreased for mid‐ to late‐feeding‐ and premetamorphic stage larvae to optimize prey encounters and feeding efficiency.     

Effects of Light Intensity and Salinity on Growth, Survival, and Whole-Body Osmolality of Larval Southern Flounder Paralichthys lethostigma

The southern flounder Paralichthys lethosligma is a high‐valued flatfish found in estuarine and shelf waters of the south Atlantic and Gulf coasts of the United States. Wide temperature and salinity tolerances exhibited by juveniles and adults make it a versatile new candidate for commercial culture, and studies are underway in the southeastern U.S. to develop hatchery methods for this species. The objectives of this study were to establish illumination and salinity conditions that optimize growth and survival of larval southern flounder reared through the yolk‐sac and first feeding stages to 15‐d post‐hatching (15 dph). Early embryos were stocked into black 15‐L tanks under light intensities of 5, 50, 100, and 1,000 Ix and at salinities of 24 and 34 ppt in a 4 ± 2 factorial design. Significant (P 0.05) effects of both light intensity and salinity on growth and survival were obtained, with no interaction between these effects. On 11 dph and 15 dph, growth was generally maximized at the intermediate light intensities (50 and 100 Ix) and minimized at the extremes (5 and 1,000 Ix). By 15 dph, growth was higher at 34 ppt than at 24 ppt. Survival to 15 dph showed trends similar to those of growth. Survival was higher at 100 Ix (avg. = 46%, range = 41–54%) than at 5 Ix (avg. = 11%, range = 6–17%) and higher at 34 ppt (avg. = 43%, range = 3145%) than at 24 ppt (avg. = 17%, range = 8–38%). Whole‐body osmolality (mOsmol/kg) was significantly lower in larvae reared at 24 ppt (avg. = 304, range = 285–325) through 11 dph than in larvae reared at 34 ppt (avg. = 343, range = 296–405). Larvae reared under the extreme light intensity treatments (5 and 1,000 Ix) at 34 ppt appeared to exhibit osmoregulatory stress, particularly on 11 dph, when a marked increase in whole‐body osmolality was observed. The mid‐intensity treatments (50 and 100 Ix) at 34 ppt optimized growth and survival of larval southern flounder in this study; and elicited the most stable osmotic response. These conditions appear to be consistent with those that southern flounder larvae encounter in nature during this early developmental period.     

温度和盐度对星斑裸颊鲷胚胎发育和仔鱼存活的影响

研究了温度(22、24、26、28、30、32℃)和盐度(15、20、25、30、33、35、40、45)对星斑裸颊鲷胚胎发育和仔鱼存活的影响。试验结果表明,星斑裸颊鲷胚胎发育所需时间与水温呈负相关,适宜温度为22~32℃,最适为28~30℃;适宜盐度为20~40,最适为30~35。星斑裸颊鲷受精卵和初孵仔鱼在盐度低于25时沉于水底,大于25时浮于水面。24℃,不投饵仔鱼存活系数为14.57,仔鱼活力较好;盐度为33时,不投饵存活数值为22.8,仔鱼活力较好。     

Intertidal Growth and Survival of Northern Quahogs Mercenaria mercenaria (Linnaeus 1758) and Atlantic Surf Clams Spisula solidissima (Dillwyn 1817) in Georgia

This work reports on the effects of intertidal planting heights upon the growth and survival of the northern quahog, Mereenaria mercenaria (L.) and the Atlantic sod clam, Spisula solidissima (Dillwyn), in the castal waters of Georgia. Quahogs (N = 100 per cage) at 19.5 mm in shell length were planted in replicate cages (N = 3) placed at the spring (SLW), mean (MLW), one (+1), two (+2), and three (+3) hours above mean low water mark. Surf clams (N = 200 per cage) at 41.5 mm in shell length were placed in replicate cages (N = 3) deployed, as above, in all sites except +3. Quahogs grown at the SLW mark after 15 months were significantly larger than clams planted at other tidal heights. Quahogs planted at the MLW mark were significantly greater in shell length than those planted at the +3, +2, and +1 marks. Clams at the upper three sites were not significantly different in size. An inverse relationship between clam growth and intertidal planting height was evident among surf clams. Surf clams grown at the SLW mark for six months were signplificmtly larger than those at the MLW mark which were larger than those grown at the +1 above MLW mark. No significant differences in quahog survival were detected between intertidal planting sites. There was no significant difference in surf clam survival between SLW (77.5%) and MLW (61%) marks, but there was significantly lower survival at the +1 mark (15%) and no survival at the +2 mark.     

盐度对鮸状黄姑鱼(Nibea miichthioides)胚胎发育和仔鱼成活的影响

本研究采用不同盐度的海水对(鱼免)状黄姑鱼受精卵的沉浮性、胚胎发育的孵化时间、孵化率、仔鱼的分布状态和成活率的影响进行研究。结果表明:(鱼免)状黄姑鱼受精卵在盐度26.9‰以下的海水呈沉性,在盐度40.7‰以上的海水呈浮性,盐度26.9‰～40.7‰则由沉性向浮性过渡。(鱼免)状黄姑鱼受精卵在盐度13.7‰～53.0‰均可孵化,但孵化适合盐度为26.9‰～40.7‰。从仔鱼的分布状态、活动情况、成活率等几方面综合分析、(鱼免)状黄姑鱼仔鱼的合适盐度为26.9—33.4‰。     

盐度对漠斑牙鲆幼鱼存活、生长及摄食的影响

盐度对漠斑牙鲆幼鱼的存活的影响较小,将漠斑牙鲆幼鱼从盐度为32的海水直接放入盐度为24、16、8、0的水中观察48 h存活情况,仅盐度0组成活率为75%,其他盐度组均为100%.在盐度为32、24、16、8、0各试验组中,经1个月饲养,生长速度和饵料系数均无显著差异.盐度越低越有利于漠斑牙鲆白化个体康复正常体色.     

温度对黄鳍东方鲀胚胎发育和仔鱼存活的影响

观察了不同温度条件下(20、23、26、29、32℃)黄鳍东方鲀受精卵的培育周期、孵化周期、孵化率和畸形率;并对黄鳍东方纯初孵仔鱼进行耐饥饿试验,测定其不投饵存活系数。试验结果表明,黄鳍东方纯受精卵孵化的适宜温度为20～26℃(最适温度为23℃);仔鱼生存的适宜温度为20～26℃(最适温度为23℃)。黄鳍东方鲀受精卵和仔鱼对温度这种环境因子的耐受范围基本相同。     

温度和盐度对墨吉明对虾（Fenneropenaeus meiguiensis）生长与存活的联合效应

采用中心复合设计(CCD)和响应曲面法(RSM),研究了温度(16–35℃)和盐度(5–29)对墨吉明对虾生长与存活的联合效应。结果显示,温度的一次效应和二次效应对墨吉明对虾的特定生长率和存活率具有显著影响(P<0.05);盐度的一次效应对墨吉明对虾的特定生长影响不显著(P>0.05),但对墨吉明对虾存活率的影响达到显著水平(P<0.05);盐度二次效应对特定生长率与存活率具有极显著影响(P<0.01);温度和盐度对墨吉明对虾的生长与存活不存在显著的交互作用(P>0.05)。采用中心复合设计建立了温度和盐度对墨吉明对虾特定生长率和存活率影响的模型方程,该方程的决定系数分别为0.9014、0.9631,校正系数分别为0.8310、0.9367,表明模型具有较好的拟合度,可用于预测墨吉明对虾特定生长率与存活率的变化。通过模型优化和验证实验,得出温度为26.6℃、盐度为15.5时,特定生长率和存活率均达到最大值,分别为1.296%,98.34%,其满意度为0.970。结果显示,墨吉明对虾在工厂化养殖过程中温度为26–27℃、盐度为15–16时,有利于墨吉明对虾的存活与生长。     

Effects of Temperature on Egg Hatch,Larval Growth and Metamorphosis for Hatchery-Cultured Southern Flounder,Paralichthys lethostigma

ABSTRACT

Egg hatch, larval growth, and metamorphosis of southern flounder, Paralichthys lethostigma, were examined at 13, 17, 21, and 25°C in laboratory experiments. The experiments were separated into four developmental phases: (1) from fertilization until hatch; (2) from hatch until mouth opening; (3) from first feeding until the onset of metamorphosis; (4) from the onset until the completion of metamorphosis. Time to egg hatch were 109, 58, 39, 30 hours at 13, 17, 21, and 25°C, respectively. Size at hatch varied little among temperatures, while percent hatch was significantly higher at 17°C (P < 0.05). There was no significant difference in total length at mouth opening among temperatures (P > 0.05). However, those larvae raised at higher temperatures reached mouth opening earlier, as it took on average 7.4, 3.9, 2.8, and 2.2 days from hatch at 13, 17, 21, and 25°C, respectively. During phase three, the growth rate was optimal at 17°C, as growth rates were 0.046, 0.110, 0.106 and 0.096 mm/day at 13, 17, 21, and 25°C, respectively. Larvae in phase four completed metamorphosis sooner at higher temperatures than at lower temperatures. It took 26.4, 15.7, and 13.1 days to complete metamorphosis at 17, 21, and 25°C, respectively, while only 16% of those at 13 progressed to stage “G” within the 27 days that phase four encompassed. No difference in total length was found among treatments (P > 0.05) at the completion of metamorphosis, but fish in the 21 °C treatment had a significantly higher survival (P < 0.05). It can be concluded that southern flounder could be produced in the highest quantity and at the largest size by raising them at 17°C from fertilization until the onset of metamorphosis, and at 21 °C during metamorphosis.     

Effects of Stocking Density, Salinity, and Light Intensity on Growth and Survival of Southern Flounder Paralichthys lethostigma Larvae

Four separate studies were done on Southern flounder Paralichthys lethostigma larvae during first feeding and metamorphosis to determine the effects of stocking density, salinity, and light intensity on growth and survival. One study used stocking densities of 10, 20, 40, and 80 fish/L during first feeding; the second study compared the growth and survival of larvae stocked at 20 and 33 ppt; and a third experiment evaluated stocking densities of 1/L and 3/L under two different light intensities (1,600 lux vs 340 lux) during metamorphosis. The fourth experiment tested the effects of different salinities (0, 10, 20 and 30 ppt) on larval growth and survival during metamorphosis. Growth and survival (overall 6.9%) were not significantly different ( P > 0.05) for stocking rates up to 80/L. Larvae placed into 20 ppt salinity had survival through first feeding similar to that of larvae raised at 33 ppt. During metamorphosis, light intensity had no effect ( P > 0.05) on growth or survival, but fish stocked at 3/L had significantly lower ( P < 0.05) survival than fish at 1/L. Complete mortality of larvae occurred at 0 ppt. Growth and survival past metamorphosis were not significantly different ( P > 0.05) at 10, 20 and 30 ppt, but unmetamorphosed fish did not survive to day 60 at 10 ppt. Based on these results, practical larviculture of Southern flounder may require a two-step process with high stocking rates (80 fish/L) through first feeding and lower densities (1/L) through metamorphosis. Fingerling production in fertilized nursery ponds might he possible at salinity as low as 20 ppt.     

Effects of Potassium, Magnesium and Age on Growth and Survival of Litopenaeus vannamei Post-Larvae Reared in Inland Low Salinity Well Waters in West Alabama

Abstract— The production of Litopenaeus vannamei in inland low‐salinity well water is a growing industry in several regions of the world. The state of Alabama in the southeastern USA is one such region with a large saline aquifer that could be utilized for shrimp culture. However, some farmers are experiencing problems rearing marine shrimp while others are having considerable success. Previous work has correlated low levels of potassium andor magnesium to poor shrimp survival. The problem is further complicated by the fact that the age at acclimation may also influence survival. In our present study, we evaluated the effects of potassium, magnesium, and the age of acclimation on growth and survival of PL at two farms. The first experiment was run in a static system utilizing four replicate tanks per treatment. Fifty PL₁₇ (0.0066 g) that had been acclimated to 4 ppt seawater were stocked into each tank and the following treatments evaluated: low salinity well water (LSWW) without mineral supplements, LSWW with KCl, LSWW with MgCl₂, and LSWW with KCl and MgCl, added to the water. Shrimp were harvested, counted and weighed after 4 wk. Survival was significantly higher in treatments receiving mineral supplements whereas biomass was only higher in the two treatments with potassium supplements. The second experiment was set up initially as a static system filled with 8.5‐ppt reconstituted sea water that was then converted to a flow‐through system using LSWW. This experiment evaluated the effect of PL age at acclimation on survival and growth at four different ages (PL₁₅, PL₁₉, PL₂₃, and PL₂₇). All tanks were stocked with 50 PL₁₃L. vannarnei. Two days after stocking, and then at 4‐d intervals, a series of four tanks were converted to flow through (rate of 40 Lhr) using LSWW. After acclimation, water flow was maintained in all tanks until 28 d after stocking when tanks were harvested and surviving shrimp were counted and weighed. Survival and growth increased with PL age when shrimp were acclimated to inland low salinity well water.     

温度和盐度对墨吉明对虾(Fenneropenaeus meiguiensis)生长与存活的联合效应

采用中心复合设计(CCD)和响应曲面法(RSM),研究了温度(16–35℃)和盐度(5–29)对墨吉明对虾生长与存活的联合效应。结果显示,温度的一次效应和二次效应对墨吉明对虾的特定生长率和存活率具有显著影响(P<0.05);盐度的一次效应对墨吉明对虾的特定生长影响不显著(P>0.05),但对墨吉明对虾存活率的影响达到显著水平(P<0.05);盐度二次效应对特定生长率与存活率具有极显著影响(P<0.01);温度和盐度对墨吉明对虾的生长与存活不存在显著的交互作用(P>0.05)。采用中心复合设计建立了温度和盐度对墨吉明对虾特定生长率和存活率影响的模型方程,该方程的决定系数分别为0.9014、0.9631,校正系数分别为0.8310、0.9367,表明模型具有较好的拟合度,可用于预测墨吉明对虾特定生长率与存活率的变化。通过模型优化和验证实验,得出温度为26.6℃、盐度为15.5时,特定生长率和存活率均达到最大值,分别为1.296%,98.34%,其满意度为0.970。结果显示,墨吉明对虾在工厂化养殖过程中温度为26–27℃、盐度为15–16时,有利于墨吉明对虾的存活与生长。     

温度与盐度对细鳞鲑仔、稚鱼生长和行为的影响

为丰富细鳞鲑(Brachymystax lenok)早期幼鱼培育的基础生物学资料和规模化人工养殖提供理论指导,探究了不同温度(9、13、17、21、25℃)、不同盐度(0、3、6、9、12)及在不同盐度下温度变化对细鳞鲑仔、稚鱼存活和生长的影响。结果表明,温度25℃和盐度9、12条件下,细鳞鲑仔、稚鱼存活率显著低于其他各组(P<0.05),温度17℃对细鳞鲑仔、稚鱼末重和特定生长率显著高于其他温度水平(P<0.05);随着盐度的升高,细鳞鲑仔、稚鱼末重和特定生长率显著降低(P<0.05);在不同盐度的水体中,水温升至19℃时,盐度6、9、12时细鳞鲑仔、稚鱼开始死亡。试验显示,在细鳞鲑仔、稚鱼培育阶段,在9～17℃范围内可适当提高水温,增加其生长速度和增重效果,缩短养殖周期;在一定的盐度水环境中,细鳞鲑仔、稚鱼对温度的适应范围缩小,适应能力减弱。     

盐度对江黄颡鱼生存和生长的影响

以平均体重为2．72g的江黄颡鱼鱼种作耐盐性试验，其96h半致死盐度(96hLC50)为12.00；直接将鱼种置于盐度为32的水体中，其平均成活时间(MST)、50％成活时问(ST50)分别为46．8min和49min。生长试验的结果表明，江黄颡鱼鱼种在盐度为0—7范围内可以安全生长，其生长和成活率不存在差异。     

Effects of Temperature on Growth and Efficiency of Yolk Utilisation in Eggs and Pre-feeding Larval Stages of Atlantic Salmon

Three embryonic stages of Atlantic salmon (Salmo salar L.) were subjected to eight constant incubation temperatures (4, 7, 10, 12, 14, 16, 19 and 22 °C) exceeding the range usually experienced in natural conditions. A change in thermal tolerance during the embryonic and larval development was registered: pre-hatching stages showed an upper thermal limit at about 16 °C, while hatched larvae survived until 22 °C. Temperature significantly affects developmental rate, resulting in a faster development and, consequently, lower yolk weight percentage at higher temperatures. We found positive relationships between incubation temperature and body size (length and weight) in the less developed stages, in which some yolk remained, but size decreased at increasing temperatures when yolk was completely exhausted.     

温度和盐度对扇贝“渤海红”稚贝存活和生长的互作效应

使用中心复合试验设计与响应曲面分析法研究温度(16~28℃)和盐度(22~34)两个因素对扇贝“渤海红”稚贝存活和生长的互作效应。试验结果显示,温度的一次效应、二次效应和盐度的二次效应对扇贝“渤海红”稚贝的存活率、壳长增长率和体质量增长率的影响达到极显著水平(P<0.01);盐度的一次效应、温度和盐度的互作效应对扇贝“渤海红”稚贝的存活率达到显著水平(P<0.05),但对稚贝的壳长增长率与体质量增长率的影响不显著(P>0.05)。存活率、稚贝的壳长增长率与体质量增长率的回归模型的相关系数分别为0.9696、0.9969、0.9966,校正系数分别为0.9391、0.9938、0.9932,预测系数分别为0.7622、0.9726、0.9662。3个模型均有较好的拟合度,可用于预测扇贝“渤海红”稚贝的存活率、壳长增长率和体质量增长率。经过软件优化,得到温度和盐度的共同影响下存活率、壳长增长率和体质量增长率的最优结果:温度22.65℃、盐度28.51时,存活率为95.33%,壳长增长率197.50μm/d,体质量增长率21.58 mg/d,其可靠性为0.975。     

盐度对漠斑牙鲆幼鱼生长与存活的影响

本文就盐度对漠斑牙鲆幼鱼的生长及存活的影响进行了探讨,结果表明:漠斑牙鲆幼鱼适宜盐度范围为0～36,最适盐度范围为6～18。在适宜盐度下,漠斑牙鲆幼鱼生长快,存活率高。过高或过低的盐度对幼鱼的生长发育均有一定的抑制作用。     

盐度对毛蚶稚贝生长和存活的影响

试验结果表明,毛蚶为广盐性滩涂贝类,盐度对其有着显著的影响。其适宜盐度17~37,最适盐度23~33。并且低盐条件较高盐条件有着更高的生长率,但存活率低于高盐环境。