牡蛎壳粉缓释剂对魁蚶(Scapharca broughtonii)生长的影响

2015年4月6日—10月26日,在桑沟湾海区现场研究了牡蛎壳粉缓释剂(Careshell)对魁蚶(Scapharca broughtonii)生长和存活的影响。按照缓释剂的重量比设置4个处理组,其中,魁蚶的初始体重均为160 g/组,缓释剂的重量分别为0(对照组C0)、80 g(C1组)、160 g(C2组)和320 g(C3组)。实验共进行200 d,每40 d测量各实验组魁蚶的生长参数(壳长、壳宽、壳高、湿重),计录死亡个体数,计算不同阶段(40 d间隔)魁蚶的特定生长率(SGR)及死亡率。结果显示,C3组魁蚶各生长参数显著高于C0组(P0.05),但与C1、C2组差异不显著(P0.05)。经过200 d的养殖实验,C3组壳长、壳宽、壳高和湿重的特定生长率分别为(0.34±0.01)%/d、(0.46±0.02)%/d、(0.39±0.01)%/d、(1.11±0.002)%/d,均极显著高于C0组(P0.01),平均增加了17.9%、20.3%、18.1%、16.7%。C3组死亡率为(19.6±5.6)%,低于C0组的(26.1±2.5)%,但差异不显著(P0.05)。     

维生素E对斑点叉尾鮰生长性能和消化酶活性的影响

试验研究了饲料中不同含量维生素E对斑点叉尾鮰生长性能和消化酶活性的影响，并对其机理进行了初步探讨。选取900尾健康的斑点叉尾鮰，平均体重(5.20±0.15)g，随机分成4个处理（I、Ⅱ、Ⅲ和Ⅳ处理依次分别添加维生素E 0、50、100和1000IU/kg饲料），每个处理3个重复，每个重复75尾。试验期105d。试验结果表明：在一定添加水平内，维生素E能够显著提高斑点叉尾鮰成活率、特定生长率(SGR)、蛋白质效率和摄饵量(P＜0.01)。当维生素E添加量为到100 IU/kg时，以上四个指标均达到最高，分别为97.78±0.96％，2.99±0.50％，163.71±5.62％和7478.00±62.01 g/尾，均极显著高于维生素E添加量为0 IU/kg组(P＜0.01）；维生素E显著影响斑点叉尾鮰胃肠道和肝胰脏蛋白酶和脂肪酶活性（P＜0.01 or P＜0.05）。当饲料中添加维生素为100IU/kg时，胃蛋白酶和脂肪酶活性最高，分别达29.33±1.66 U•min－1 •mg－1，196.52±17.28 U•min－1 •mg－1，极显著高于维生素Ｅ添加量为0 IU/kg组(P＜0.01）和显著高于维生素Ｅ添加量为1000IU/kg组(P＜0.05）。由本试验结果可以看出，维生素E在一定添加水平内能显著提高斑点叉尾鮰消化酶活性，促进此鱼生长，且其适宜添加量为100 mg／kg。     

魁蚶中国群体与韩国群体杂交子一代养成期生长比较

以魁蚶(Scapharca broughtonii)中国群体(C)和韩国群体(K)为材料,进行了4个组合的杂交和自交实验,测定了各实验组魁蚶在养成期(10~15月龄)的壳长、湿重,并计算了杂交组合的杂种优势。结果显示,养成期杂交KC组壳长显著高于自交CC组、KK组和杂交CK组,CK组壳长杂种优势率在–2.03%~5.44%之间,KC组壳长杂种优势率在4.40%~14.74%之间,且KC组壳长杂种优势率始终高于CK组;养成期杂交KC组湿重始终显著高于自交CC、KK组和杂交CK组,而杂交CK组仅在14、15月龄显著高于自交CC和KK组,2个杂交组合湿重的杂种优势率始终为正值,CK组湿重杂种优势率在1.41%~7.71%之间,KC组壳长杂种优势率在5.32%~23.71%之间,且KC组湿重的杂种优势率始终高于CK组,在湿重性状方面杂种优势更明显。综合分析表明,杂交KC组的杂交子一代在壳长和湿重方面的杂种优势更加明显,是理想的育种材料。     

摄食水平对中华鳖幼鳖生长的影响

在 30℃水温下进行摄食生长实验 (实验周期为 5 6d) ,设饥饿、 1%、 2 %和饱食 4个摄食水平 ,研究了摄食水平对中华鳖幼鳖 (2 96 6 0～ 396 0 9)g生长的影响。结果表明 ,摄食水平对中华鳖幼鳖的特定生长率有显著影响 (P <0 0 1) ,其特定生长率随摄食水平的增加而增加 ,除湿重特定生长率外 ,干物质、蛋白质和能量的特定生长率摄食率之间的关系以二次方程表述可靠性最高 ,而湿重的特定生长率摄食率关系以对数方程表述时可靠性最高。方差分析表明 ,摄食水平对中华鳖幼鳖湿重和能量的转化效率有显著影响 (P0 0 5 ) ,除湿重的转化效率外 ,干物质、蛋白质和能量的转化效率在 2 %组均达到最大。     

三疣梭子蟹幼蟹的摄食和碳收支

20 0 2年 6～ 9月 ,在自然水温 (2 4 0、2 4 9和 2 6 3℃ )和投喂鹰爪虾虾仁的条件下测定了 3个体重组 (0 73± 0 15 g、1 5 5± 35 g和 3 75± 0 5 2g)三疣梭子蟹幼蟹的摄食和碳收支。结果表明 ,温度和体重对三疣梭子蟹幼蟹的摄食量均有明显影响 ,其中体重的影响更为显著。以湿重和干重(比能值 )计算得到三疣梭子蟹幼蟹的特定生长率 (SGR)和生态转换效率 (Eg)分别为 2 5± 1 33～3 0± 0 95和 19 4± 4 8～ 5 9 4± 2 2 9,2 8± 0 73～ 4 3± 2 2 8和 10 1± 2 3～ 2 9 1± 12 4。在三疣梭子蟹幼蟹的C收支模式中 ,代谢C所占的比例最大 ,占总摄食C的 5 0 %以上 ,其次是生长C ,约占总摄食C的 2 8% ,蜕壳和排粪消耗的C的比例较小 ,一般少于 5 %。三疣梭子蟹幼蟹的个体大小和水温是影响C收支的重要因素 ,其中温度是主要因子。随个体的增大和试验水温的升高 ,三疣梭子蟹生长C占总摄食C的比例减少 ,代谢C的比例增加 ,蜕壳C和排粪C所占的波动较小。     

低氧预适应对魁蚶在低氧胁迫下生理生化指标的影响

本研究以未进行低氧预适应的魁蚶(Scapharca broughtonii)为对照组(C组)，分析了2次低氧预适应(H2组)和4次低氧预适应(H4组)的魁蚶在溶解氧(DO)约为2.0 mg/L低氧胁迫48 h内的摄食、呼吸代谢和酶活力的变化规律。结果显示，3组魁蚶的摄食率(IR)在胁迫初期急剧下降，后期均随时间的延长逐渐恢复，至48 h时，H组恢复程度显著高于C组(P＜0.05＝；C组、H2组和H4组魁蚶的耗氧率(OR)随时间变化呈逐渐升高的趋势，48 h比0 h分别提高了1.15、1.08、0.73倍；3组排氨率(NR)表现出不同的变化趋势，至48 h时，C组、H2组和H4组分别为0 h的1.67、1.30、0.97倍；C组的氧氮比(O/N)相对平稳，H组的变化范围相对较大。3组的细胞色素C氧化酶(COX)随着低氧胁迫时间的延长呈逐渐降低的趋势，乳酸脱氢酶(LDH)活力和还原型谷胱甘肽酶(GSH)含量整体呈上升趋势，与对照组相比，预低氧组的酶活力在低氧胁迫期间变化相对平稳，应激反应小。研究表明，魁蚶经低氧预适应后再次受到低氧胁迫时，IR升高，OR降低，酶活性相对稳定，低氧预适应能提高魁蚶的耐低氧能力。本研究丰富了魁蚶低氧耐受相关研究的基础数据，为进一步探讨魁蚶低氧耐受机制和创制耐低氧新种质提供了参考资料。     

Cu2+胁迫对魁蚶生理生化和组织结构的影响

采用生物毒性测试的方法,研究了持续暴露96 h不同浓度Cu2+胁迫对魁蚶生理代谢、组织结构及酶活性的影响。实验设置0.01、0.05、0.10、0.50和1.00 mg/L组5个浓度梯度,不加Cu2+的正常海水作为对照。结果显示,Cu2+胁迫对魁蚶耗氧率(OR)、排氨率(NR)、氧氮比(O∶N)均有显著影响,并且与暴露时间和浓度有关。初次暴露时,OR,NR和O∶N都迅速下降,最低值都出现在1.00 mg/L浓度组,分别为(0.005±0.001)mg/(g·h)、(0.5±0.05)μmol/(g·h)、0.7±0.1,仅为对照组的1%、29%和3%。暴露72 h内Cu2+胁迫均使魁蚶代谢率不同程度下降,之后不同处理组出现差异分化。暴露96 h时,魁蚶对低浓度Cu2+暴露表现出适应,0.01 mg/L处理组呼吸代谢恢复至正常水平,O∶N与对照组无差异,组织结构也未见明显损伤;浓度超过0.05 mg/L处理组魁蚶生理代谢及组织结构受显著影响,O∶N大多降至9以下,出现鳃丝受损和组织结构散乱等明显损伤;0.10 mg/L处理组魁蚶体内ACP和ALP活性在鳃组织中增强,肝脏中受到抑制,而GPX和GST活性增强。研究表明持续暴露96 h Cu2+浓度≥0.05 mg/L环境显著影响魁蚶生理代谢及组织结构,0.10 mg/L Cu2+浓度显著影响魁蚶组织中ACP、ALP、GPX和GST的活性。研究结果为认知魁蚶等滩涂贝类对Cu2+胁迫的响应机制提供基础数据,为预防滩涂潜在重金属污染风险及生物修复提供参考。     

凡纳滨对虾(Litopenaeus vannamei)选育群体与杂交群体遗传多样性差异及其在低温条件下生长性能的比较

选取连续3年选育的凡纳滨对虾(Litopenaeus vannamei)群体作为选育群体(SP),选育群体与引进的凡纳滨对虾群体的杂交F1代群体(HP),探究了这2个群体在低温条件下的生长性能及遗传多样性的差异.结果显示,在生长性能方面,HP群体与SP群体的平均体重分别为(13.18±3.65)g和(12.20±3.14)g,变异系数(CV)分别为27.69％和25.74％.HP群体的体重和其他可测量性状的平均值均大于SP群体.单因素方差分析(One-way ANOVA)表明,2个群体体重(BW)和第3腹节宽(TASW)存在极显著差异(P＜0.01).HP群体的特定增长率(SGR)和绝对增重率(AGR)分别为(5.09±0.61) ％/d和(0.26±0.60) g/d,SP群体的SGR和AGR分别为(4.94±0.57) ％/d和(0.24±0.63) g/d,HP群体的SGR和AGR均极显著高于SP群体(P＜0.01),表明HP群体相对于SP群体有着明显的生长优势.在遗传多样性方面,HP群体的平均等位基因数(Na=7.9)略高于SP群体(Na=7.6).HP群体和SP群体的平均多态信息含量(PIC)分别为0.63和0.62,均为高度多态.2个群体的平均观测杂合度(Ho)分别为0.492(HP群体)和0.483(SP群体),平均期望杂合度(He)分别为0.675(HP群体)和0.663(SP群体),HP群体的He和Ho均略高于SP群体,表明HP群体相比SP群体有着更加丰富的遗传多样性.遗传分化分析表明,2个群体间遗传分化指数(Fst)为0.1556,表明群体间遗传分化水平显著.     

温度对魁蚶稚贝潜沙能力及对多棘海盘车捕食魁蚶稚贝能力的影响

在实验室条件下,研究了温度变化(10、15、20、25和30℃)对魁蚶稚贝(壳长2~3 cm)潜沙能力,及多棘海盘车对魁蚶稚贝捕食速率的影响。结果发现,水温10℃时,魁蚶稚贝的初次潜沙时间(初潜时间)最长,潜沙率最低,分别为28.87 min、21.25%,且与其他温度处理组差异显著(P0.05)。20℃时,魁蚶稚贝初潜时间最短、潜沙率最高,分别为7.49 min、55.63%,可视为魁蚶稚贝的最适潜沙温度。多棘海盘车对魁蚶稚贝的捕食速率受温度影响显著,水温20℃时捕食速率最大,为5.28个/d,且与10℃、25℃处理组间存在明显差异(P0.05)。水温15~20℃时,多棘海盘车的捕食温度系数Q10为2.22,可视为其最适捕食温度。魁蚶稚贝的最适潜沙温度与多棘海盘车的最适捕食温度范围重叠。因此,在水温20℃左右进行魁蚶稚贝底播增殖时,也是多棘海盘车捕食速率的最高时期,应加强底播海区多棘海盘车的清除。     

投喂发酵饲料对刺参能量收支、生长、酶活性及其养殖水质的影响

为探究发酵饲料在刺参(Apostichopus japonicus)苗种培育中的效果，本研究测定了投喂发酵饲料对刺参苗种能量收支、生长、非特异性免疫酶和消化酶活性的影响，同时，对比分析了1个倒池周期内投喂发酵和未发酵饲料养殖单元池水的重要水质指标差异。结果表明，在50 d的养殖实验周期内，投喂发酵饲料组刺参苗种的存活率(SR)为(91.51±0.74)%，显著高于未发酵饲料组[(82.35±2.22)%] (P<0.05)，苗种的特定生长率(SGR)为(1.83±0.01)%/d，与未发酵饲料组无显著差异。投喂发酵饲料刺参的生长能和代谢能占比分别为(13.25±1.01)%和(32.32±2.00)%，表明投喂发酵饲料可显著提高刺参生长能；对重要非特异性免疫酶指标和消化酶指标活性的测定结果表明，投喂发酵饲料组刺参的碱性磷酸酶、溶菌酶和胰蛋白酶活性分别为(0.74±0.04) king U/100 ml、(95.52± 14.80) U/ml和(335.89±13.01) U/mg prot，显著高于投喂未发酵饲料组(P<0.05)；对实验期间一个倒池周期(7 d)内各实验组重要水质指标变化的测定结果表明，第7天投喂发酵饲料组水体氨氮和亚硝酸盐浓度分别为(263.27±32.57)和(315.15±61.41) μg/L，显著低于未发酵饲料组。综合各项指标可以看出，投喂发酵饲料可显著提升刺参苗种的生理代谢水平，并有利于维持养殖池水水质，表明发酵饲料在刺参育苗与养殖中具有广阔的应用前景。     

三角帆蚌三个优异群体杂交后代生长性能比较研究

于2003年5月21日至2004年12月23日,在浙江诸暨的养殖池塘比较研究了三角帆蚌(Hyriopsis cum-ingii)的洞庭湖群体(DD)、鄱阳湖群体(PP)和太湖群体(TT)自交F1与其6个杂交F1(DP,PD,DT,TD,TP和PT)的生长性能。结果显示:19月龄的9个群体三角帆蚌壳长已趋于相对恒定,但早期各群体间壳长差异明显。壳宽性状从6月龄至19月龄,PP、PD和TD三者均无明显差异,但均优于其余6群体(P<0.01)。特别发现PD从4月龄至19月龄均呈现明显的生长优势。从整个试验阶段来看,PD的体重也具有生长优势;经572 d生长发育,生长最快的依次为PD((0.42±0.07)g/d)、TD((0.37±0.04)g/d)和PP((0.37±0.08)g/d),生长最慢的是TT((0.30±0.08)g/d)、DP((0.32±0.06)g/d)和PT((0.32±0.07)g/d)。各性状的杂种优势率在-1.95%～17.08%之间。对于壳宽性状,PD、TD和PT均产生了杂种优势,且以PD最大,达到7.99%。在体重性状上,PD的杂种优势最大,达到了17.08%,其次为TD(14.10%),因此,PD与TD的养殖性能最好。     

洪泽湖河蚬种群生长方程的估算及其应用

015年4月（春季）、8月（夏季）、11月（秋季）和2016年2月（冬季），对洪泽湖河蚬（Corbicula fluminea）进行了采样调查，共设置30个样点，从各采样点分别随机选取30个河蚬，记录不同壳长、壳宽、壳高和体重的河蚬数量，计算其年龄组成和分布频率，并统计不同壳长组的年龄分布情况，以期为其资源的合理利用与保护提供参考依据。结果显示，形态指标和体重呈现显著的季节变化；壳长、壳宽、壳高、体重和年龄范围分别为1.47~40.82 mm、3.93~27.81 mm、8.46~37.40 mm、0.43~20.56 g和1~5龄，壳长、壳宽、壳高、体重和年龄的优势组分别为15~35 mm（92.6%）、12~20 mm（83.2%）、15~31 mm（88.8%）、2~10 g（79.6%）和2~3龄（76.5%）；其相对增长率和生长指标随年龄的增加逐渐降低；壳长-体重关系式为W = 1.5×10-3L 2.5795(R2= 0.90)，Von Bertalanffy壳长和体重生长方程分别为Lt= 39.42 ×[1 - e- 0.33 (t + 0.6)]和Wt= 22.574 × [1-e- 0.33 (t + 0.6)]3；拐点年龄为2.73龄，对应的体重和壳长分别为6.69 g和26.28 mm。分析表明，洪泽湖有适宜河蚬生长的环境条件，且秋季为最佳捕捞季节；年龄与壳长和体重显著正相关，可以通过河蚬的体长和体重来估测其年龄；其生长可分为3个阶段，1~2龄为快速生长期，2~3龄为稳定期，3~5龄为衰老期。建议将拐点年龄所对应的壳长26.28 mm作为洪泽湖河蚬开捕壳长。     

长牡蛎壳黑和壳白选育群体生长性状的选择效应

为了培育壳色性状优良且生长性状良好的长牡蛎(Crassostrea gigas)新品系,本研究以5个壳黑第四代家系和5个壳白第四代家系的成贝为基础群体,利用截头法对壳高进行选择,构建了壳黑和壳白快速生长系第一代群体,分析了两个选育群体的壳高和活体体重的选择反应、遗传获得和现实遗传力等遗传参数。结果表明,在长牡蛎收获的490日龄,壳黑群体和壳白群体选择组壳高较对照组壳高分别提高(9.83?1.68)%和(9.97?1.87)%,体重分别提高(10.16?3.64)%和(11.36?1.96)%。两选育群体壳高的平均现实遗传力分别为(0.353?0.09)和(0.405?0.111),体重的平均现实遗传力为(0.192?0.080)和(0.244?0.123)。本研究表明壳黑群体和壳白群体具有较大的遗传方差,在对壳高生长速度直接选择的同时实现了对活体体重的间接选育,可继续通过群体选育提高生长速度。本研究结果可以为培育出壳色美观、生长性状良好的长牡蛎优良品种提供科学依据。     

Evaluation of growth and dressing out parameters of experimental scaly crossbreds in 3-year-old common carp (Cyprinus carpio, Linnaeus 1758)

Performance tests of the Pr?erov Scaly Carp (PS), two crossbreds (PS × M72 and PS × ROP) and an internal control group (M2 × M72) were designed to assess their production and dressing out parameters at harvest size for their potential commercial utilization. The fastest growth rate (standard length (SL): 405±21.91 mm, P<0.01) and the highest final live weight (FLW: 2015.70±323.92 g, P<0.01) were recorded in the PS × ROP hybrid. The SL values in this group of carp were 12.5%, 19.12% and 11.57% higher (P<0.01) than those at M2 × M72, PS and PS × M72, respectively, and the FLW values were 21.57%, 62.83% and 24.37% higher (P<0.01) compared with M2 × M72, PS and PS × M72 hybrids respectively. Growth rate parameters of PS × M72 hybrid and control group M2 × M72 were practically identical. The lowest growth rate potential and FLW were recorded in the PS group (P<0.01). The highest (P<0.01) dressing out parameters were found in the control group of mirror carp M2 × M72 with a dressing percentage of 65.64±2.11%. There were practically no differences in this parameter between scaly carp groups (PS: 61.79±2.82%, PS × M72: 61.51±1.72%, PS × ROP: 63.60±1.96%). This study shows evidence for faster somatic growth and bigger final weight in the hybrid line PS × ROP of 3‐year‐old common carp compared with the pure line PS and the crossbreed PS × M72.     

Effects of water exchange regimes on growth, survival and shell normality of the hatchery reared juvenile spotted babylon (Babylonia areolata Link 1807) in a recirculating seawater system

Growth, survival and shell normality of hatchery reared juvenile Babylonia areolata were examined at four water exchange regimes of 0, 15, 30 and 60 day intervals in a recirculating seawater system over a 120 day experimental period. Higher body weight gains and shell length increments were observed in snails held at water exchange of 15 day intervals, especially when compared with those held at water exchange of 60 and 0 day intervals (P < 0.05). Water exchange affected the final survival of B. areolata. At the end of the experiment, final survival rates were 65.47 ± 0.66%, 87.48 ± 0.67%, 86.34 ± 0.92% and 78.50 ± 3.26% for snails held in the water exchange treatments of 0, 15, 30, and 60 day intervals, respectively, and those of shell abnormality were 97.65 ± 1.04%, 93.09 ± 2.34%, 97.08 ± 1.18% and 96.71 ± 1.84%, respectively. The present study concluded that water exchange regimes of the recirculating system influenced growth, survival, shell normality and water quality of the recirculating culture system for this species.     

Physiological responses to feed restriction and starvation in juvenile Siberian sturgeon Acipenser baerii (Brandt, 1869): Effects on growth,body composition and blood plasma metabolites

An 8‐week study was applied to evaluate the effects of feed restriction and starvation on growth, proximate composition, haematological and biochemical factors in juvenile Siberian sturgeon Acipenser baerii with an average weight of 54 ± 0.6 g. Fish were randomly divided into nine indoor tanks (1,050 L volume) with 30 fish per tank in a flow‐through system at 18 ± 0.4°C. Three feeding strategies were considered: I) fed at satiation (F), II) restricted feeding at the rate of 1% body weight per day (R) and III) starvation (S) each with 3 replicates. Fish were fed with commercial pellets 4 times daily, but no feed was considered for S group throughout the trial. Basal level at the start, 4 and 8 weeks after initiation of the experiment, blood samples were taken from 5 fish/tank to measure the haematological and biochemical parameters. Moreover, growth performance was recorded every 2‐week interval. At the end of the experiment, the growth parameters and proximate composition were significantly different among the treatments. As expected, the highest weight (164.7 ± 2.1 g) was observed in F group compared to R (101 ± 1.7 g), or S (42.4 ± 0.8 g) groups. The highest (12.07 ± 0.14%) and lowest (5.37 ± 0.42%) fat contents were observed in F and S groups, respectively, while the protein was not affected in R group compared with F group. In addition, most haematological and biochemical indices of Siberian sturgeon were affected by starvation at week 4 and 8, while few changes were observed in restricted feeding. The highest mean corpuscular volume, mean corpuscular haemoglobin, plasma total protein, cholesterol and triglyceride was found in S group, while the lowest value of plasma glucose was observed in this group. It can be concluded that Siberian sturgeon adjusts the physiological condition in short‐term (4 weeks) feed restriction using stored metabolites to have basal metabolism and due to this, a short period of feed restriction strategy recommends to the optimum nutritional management of Siberian sturgeon to cost‐saving during unsuitable conditions.     

魁蚶中间育成试验研究

当年常温育苗的稚贝生长期主要在8～11月,12月～翌年2月为越冬期。采用 W—a·L~b 这一幂函数描述稚贝壳长与体重的相关关系(W 代表体重、L 代表壳长)。风浪小、饵料丰富的内湾及虾池是稚贝适宜的中间育成水域。早育苗、早出库增加稚贝有效生长时间是获得大规格种苗的关键。稚贝壳长达5.0～6.0mm 时应及时分苗,调整网目及密度,保持网袋流水畅通。沙蚕、海星、蟹类是稚贝的敌害,夏季高温容易造成1龄贝大量死亡。     

Studies on triploid oysters in Australia: effect of initial size on growth of diploid and triploid Sydney rock oysters, Saccostrea commercialis (Iredale & Roughley)

In a 2-year grow-out trial, triploid Sydney rock oysters, Saccostrea commercialis (Iredale & Roughley), from two initial size grades grew faster (in terms of both mean whole weight and shell height) than the equivalent initial size grades of sibling diploids (P < 0.05). Small size grade triploids caught up with and had significantly heavier (P < 0.05) final whole weights than large size grade diploids after a 2-years grow-out period. The initial size grade had a significant effect on final mean whole weight and shell height for both ploidy types. After the 2-years grow-out trial, the final mean whole weights (but not shell heights) of small and large diploids (35.8 ± 0.6 g and 39.4 ± 0.5 g, respectively) were significantly different (P < 0.05). Small and large triploids grew at a similar rate for the first 18 months despite the significantly (P < 0.05) heavier final mean weight of large grade triploids (48.4 ± 0.8 g and 61.2 ± 0.7 g, respectively). The effect of the initial size grade on subsequent growth of both diploid and triploid oysters which was demonstrated in the present study is of significant commercial value to hatchery and nursery operators as well as growers of single seed oysters. In addition, small-grade triploids appeared to be more valuable in terms of potential growth rate than all diploid grades. There was no significant difference in the final percentage triploidy between small and large grade triploids. A large proportion of diploid/triploid mosaicism was detected in adult oysters.     

The effects of elevated concentrations of dissolved inorganic phosphate in seawater on the growth and survival of juvenile abalone,Haliotis iris

Seawater sampling from three abalone farms in New Zealand showed average ambient concentrations of dissolved inorganic phosphate (P_i) varying between 2.36 and 238 μM. The P_i concentration within each system appeared to be directly linked to the percentage of water that was replaced each day. An experiment was conducted over 5 months to examine the effect of elevated P_i concentrations on the growth of two juvenile abalone (Haliotis iris) size classes (small: average shell length=23.9 ± 0.1 and large: average shell length=61.9 ± 0.1 mm). Abalone from each size class were exposed to P_i concentrations of; (a) natural incoming seawater (average 0.12 ± 0.12 μM), (b) 10.7 ± 1.3 μM, (c) 60.9 ± 5.8 μM and (d) 113.1 ± 5.6 μM. The results suggest that over the course of the 5‐month period of this experiment there was a significant negative impact on growth (shell length and wet weight) when the smaller size class of abalone were exposed to P_i concentrations greater than 10.7 μM and for the large size class of abalone when exposed to greater than 60.9 μM P_i. However, elevated P_i concentrations did not significantly impact on abalone survival during the course of the experiment.