嘉陵江中游7种主要经济鱼类的生长特性及资源量

于2017年7-11月和2018年7-11月在嘉陵江中游开展鱼类资源现状调查,根据渔获物信息确定水域主要经济鱼类种类,运用FiSATⅡ软件分析鲤(Cyprinus carpio)、鲫(Carassius auratus)、黄尾鲴(Xenocypris davidi)、翘嘴鲌(Culter alburnus)、蒙古鲌(Chanodichthys mongolicus)、黄颡鱼(Pseudobagrus fulvidraco)、蛇鮈(Saurogobio dabryi)7种主要经济鱼类的生物学参数和生长特性;通过单位捕捞努力量渔获量(CPUE)[尾/(船×天)]计算每种鱼的年捕捞量,利用FiSATⅡ软件初步估算其资源量,并以此推算嘉陵江中游鱼类的总资源量.结果显示,7种鱼的生长指数b在2.86-3.03之间,均为匀速生长;7种鱼的生长系数K皆大于0.2,为快速生长型;生长性能指数φ′在4.40-5.30之间;仅蛇鮈的E值小于E_(max),资源利用不足,其余鱼种E值皆大于E_(max),资源过度开发;黄颡鱼的拐点年龄ti最大(4.26龄),蛇鮈最小(1.58龄),其余大多在3龄以内;鲤、鲫、黄尾鲴、翘嘴鲌、蒙古鲌、黄颡鱼和蛇鮈的年资源质量依次为3 883 t、9246 t、2 469 t、1 259 t、862 t、376 t、1 391 t,嘉陵江中游鱼类的年总资源质量为37 400 t.本研究表明嘉陵江中游主要经济鱼类因遭到过度捕捞而同时存在群落结构和种群结构层面的小型化;结果可为长江禁渔成效评估提供数据参考,为制定嘉陵江中游合理的渔业管理措施、实现渔业的可持续发展提供科学依据.(图7表4参51附表4)     

山东半岛南部近岸海域鱼卵、仔稚鱼群落结构与环境因子相关性

为了解鱼卵、仔稚鱼的种群动态及其与环境因子之间的关系,2017年4—7月,利用大型浮游生物网对山东半岛南部近岸海域进行水平拖网调查。5个航次调查共采集鱼卵5042粒,仔稚鱼108尾,共24个物种,隶属于7目18科24属。鱼卵的优势种为鳀(Engraulisjaponicus)和斑鰶(Konosiruspunctatus),仔稚鱼没有出现优势种,六丝钝尾虾虎鱼(Amblychaeturichthyshexanema)和鳀构成仔稚鱼的重要种。鱼卵、仔稚鱼的最高优势度物种之间的季节更替明显。鱼卵、仔稚鱼对应的成鱼平均营养级为3.41,处于第三营养级低级肉食性鱼类范畴;春季和夏季采集的鱼卵、仔稚鱼对应的成鱼营养结构相似。利用GAM模型研究了山东半岛南部近岸海域鱼卵、仔稚鱼分布与环境因子的关系。结果显示,鱼卵、仔稚鱼的最适温度在16—20℃之间。水深对数量分布的影响总体呈先下降后缓慢升高的趋势;盐度31.5—32为鱼卵、仔稚鱼的最适盐度。月份、纬度和深度等因子对鱼卵、仔稚鱼的分布均有显著影响(P0.01或P0.05)。聚类分析结果表明,春、夏两个季节均分为3个站位组,但是随季节变化站位分组有较大差异。春季两个近岸组之间的主要分歧种为斑鰶、短吻红舌鳎(Cynoglossus joyeri)、黄姑(Nibea albiflora)和多鳞鱚(Sillago sihama);夏季区分近岸和远岸的主要分歧种为斑鰶、鳀、短吻红舌鳎,这几个物种都较多出现在近岸组。文章对山东半岛南部近岸海域鱼卵、仔稚鱼群落结构的空间格局及与环境因子的相关性进行了解析,为科学认识和保护该海域渔业资源及制定资源量化管理等措施提供依据和技术支撑。     

大田软海绵酸对黑鲷胚胎发育及仔鱼的急性毒性

为了研究大田软海绵酸(okadaic acid,OA)对生物胚胎组织发育过程的毒性作用机制,采用静水和半静水实验法,用OA毒素与过滤海水按等对数间距分设5个浓度组,同时以过滤海水为对照组,对人工养殖的黑鲷鱼卵和仔鱼进行了毒性实验。实验结果表明:一定浓度的OA使鱼卵的死亡率和孵出仔鱼的畸形率升高,但对孵化率的影响较弱。OA对黑鲷仔鱼的24、48、72和96h的LC50分别为51.63、45.58、37.97和25.72nmol·L-1,仔鱼体内毒性蓄积程度也随时间逐渐减弱。OA毒素对仔鱼的谷胱甘肽过氧化物酶(GSH-PX)和酸性磷酸酶(ACP)的活性均有诱导作用,与对ACP的影响相比,OA毒素对GSH-PX活性的诱导作用更为突出。此外,OA毒素还会对黑鲷仔鱼的肝脏细胞的核酸代谢及DNA合成有一定的影响,使得RNA和DNA的含量比值发生显著变化。     

应用鱼类生物完整性指数评价荔浦河河流健康

生物完整性指数是河流生态系统健康评价主要方法之一。为评价荔浦河河流健康状况,选择鱼类作为指示生物,构建了基于鱼类生物完整性指标体系。2017年1月、4月、7月和10月对荔浦河4次采样共采集到鱼类21 192尾,经鉴定共计94种,隶属于6目17科62属。以S1(修仁镇)、S10(马岭镇)、S11(双江镇)作为参考点,经过分布范围分析、箱体图判别能力分析及相关性分析等指标筛选过程从25个候选指标筛选出5个指标,即鱼类总物种数、Shannon-Wiener多样性指数、肉食性鱼类数量百分比、敏感性鱼类数量百分比、产漂浮型卵鱼类数量百分比。将荔浦河河流健康等级分为"健康"、"一般"、"较差"、"极差"和"无鱼"5个等级。结果表明,荔浦河青山镇、荔浦县及蒲芦乡河段健康状态为"一般"水平,东昌镇、龙怀乡、杜莫镇及新坪镇河段健康状态为"较差"水平,茶城乡河段健康状态为"极差"水平。筑坝工程、架桥工程和修路工程等人类活动导致荔浦河支流上的健康状况比干流更差。上述研究结果可为荔浦河的河流管理和保护提供理论依据和技术支持。     

松花江沉积物中总汞及汞形态的演化

为进一步掌握松花江汞污染的动态,通过2005年的样品采集与分析,结合有关历史数据,研究了松花江表层沉积物中汞的分布与变化.结果表明,在切断汞的主要污染源之后,第二松花江和松花江干流沉积物中汞含量均呈明显下降趋势;松花江18个断面沉积物中总汞质量含量较低,平均为0.172 mg·kg-1,除哈达湾、哨口和白旗江段外,大部分江段已处于背景水平.各江段沉积物中汞的形态分布差别较大,第二松花江沉积物中汞以过氧化氢溶态和王水溶态为主,而干流江段则以酸溶态和过氧化氢溶态为主;与20世纪80年代相比,除了王水溶态汞以外,2005年哈达湾、哨口和白旗3个代表性断面酸溶态、碱溶态及过氧化氢溶态汞含量均大幅下降.说明经过多年的环境治理以及水体的自然净化作用,松花江的汞污染已经得到了有效控制.     

双酚A及其类似物对斑马鱼胚胎及幼鱼的毒性效应

为探讨双酚A及其类似物对鱼类早期生长发育的毒性效应,研究了双酚A及其7种类似物对斑马鱼胚胎及仔鱼的毒性效应。通过对胚胎的孵化率、心率、仔鱼体长等指标进行测定分析,结果显示:(1)双酚A及其7种类似物都可使斑马鱼胚胎出现心包水肿、卵黄囊肿、脊柱弯曲和尾部弯曲等症状。(2)综合考虑斑马鱼78 hpf胚胎心率、120 hpf胚胎孵化率及7 dpf仔鱼体长抑制率等指标,8种受试物中双酚P(BPP)的毒性最大,其次是双酚AP(BPAP)、双酚AF(BPAF)、双酚Z(BPZ),然后是双酚A(BPA)、双酚B(BPB)、双酚F(BPF),双酚S(BPS)的毒性最小,每种受试物的浓度与受精卵的孵化率、仔鱼心率呈明显负相关关系,与体长抑制率呈明显正相关关系。8种受试物毒性与辛醇-水分配系数(log K_(OW))呈正相关关系,log K_(OW)越大毒性则越大。     

吡唑醚菌酯对不同阶段斑马鱼的毒性效应评价

为评价吡唑醚菌酯对鱼类不同生命阶段的毒性效应,以斑马鱼(Brachydanio rerio)为测试生物,测定了其对斑马鱼胚胎、仔鱼(孵化3 d和孵化12 d)和成鱼的急性毒性及对胚胎和仔鱼(孵化3 d)的发育毒性。结果表明,吡唑醚菌酯对斑马鱼胚胎、仔鱼(孵化3 d)、仔鱼(孵化12 d)和成鱼的96 h-LC50分别为0.0578(0.0540~0.0631)、0.0299(0.0282~0.0320)、0.0330(0.0310~0.0350)和0.0756(0.0692~0.0862)mg·L-1,其毒性大小依次为仔鱼(孵化3 d)仔鱼(孵化12 d)胚胎成鱼。与对照组相比,吡唑醚菌酯0.101 mg·L-1处理,可对斑马鱼胚胎24 h自主运动产生显著抑制作用;0.0609、0.0777和0.101 mg·L-1处理,可对斑马鱼胚胎48h心跳速率产生显著抑制作用;0.0609和0.0777 mg·L-1处理,可对斑马鱼胚胎96 h孵化仔鱼体长产生显著抑制作用。在供试浓度下吡唑醚菌酯暴露96 h后,均可对斑马鱼仔鱼(孵化3 d)体重和体长产生明显的抑制效应,对斑马鱼仔鱼(孵化3 d)心跳未产生明显影响。在高浓度下,吡唑醚菌酯可诱导斑马鱼胚胎产生畸形,主要包括心包水肿、卵黄囊水肿等;而对仔鱼(孵化3 d)未观察到明显的致畸效应。     

铜和镉对珠江天然仔鱼和幼鱼的毒性效应及其潜在生态风险

以静水实验法探讨珠江流域主要金属污染物铜和镉对当地天然仔鱼和幼鱼的急性毒性效应。结果显示,铜对西江赤眼鳟和鲴仔鱼(48 h)和广东鲂幼鱼(96 h)的LC50分别为0.066、0.055和0.10 mg·L-1,对应的安全浓度分别为0.006、0.010和0.010 mg·L-1;镉对赤眼鳟和鲴仔鱼(48 h)以及广东鲂幼鱼(96 h)的LC50分别为1.29、0.83和3.20 mg·L-1,对应的安全浓度分别为0.163、0.077和0.320 mg·L-1。其中,铜对上述受试鱼的安全浓度低于或接近我国《渔业水质标准》及《地表水环境质量标准》Ⅱ类水对铜的规定,而镉对这些受试鱼的安全浓度则高于相关标准对镉的规定。研究结果表明,珠江流域铜污染可能会对当地天然仔鱼、幼鱼群体的补充构成一定程度的威胁,但镉污染暂不会对该区域主要鱼类早期群体补充带来严重的生态风险。     

连江西牛鱼道过鱼效果及其影响因子研究

连江西牛鱼道是我国华南地区首座在水坝主体加建的过鱼通道。为了解其过鱼效果,于2013年1—12月采用张网法和堵截法对西牛鱼道过鱼种类、数量及其环境因子进行12次监测,共监测到鱼类41种,属4目9科33属,通过鱼道的鱼类以银鮈(Squalidus argentatus)、乐山小鳔鮈(Microphysogobio kiatingensis)、子陵吻鰕虎鱼(Rhinogobius giurinus)等小型鱼类为优势种群。不同季节鱼道过鱼种类和数量差别较大,4—6月过鱼种类和数量显著高于其他月份。对不同月份鱼道鱼类群落进行聚类分析(CLUSTER),可以将其分为3个类群。过鱼生物多样性指数8月最高、1月最低;丰富度指数5月最高、1月最低。对各月份采集的鱼类群落与水文因子进行冗余分析(RDA),发现流速、流量、上游水位和透明度这4个因子对过鱼效果影响显著(P0. 05)。     

长江上游宜宾至泸州江段突发水污染风险评估

为防控长江上游重大突发水污染事件的发生,收集整理长江宜宾至泸州江段沿江水环境污染源及受体基础资料,构建水环境潜在污染风险分级评价体系。采用地统计学理论和地理信息系统(Geographic Information System,GIS)相结合的方法开展突发水污染风险分区评价研究,以揭示研究区江段突发水污染风险空间分布差异性。结果表明,污染源或受体热点分布主要集中在城镇化、工业化较快的地区,如宜宾市叙州区污染源最多,泸州市龙马潭区高风险污染源最密集,宜宾县和南溪县高敏感受体数量最多;其他区域污染源或受体分布较为均衡,未形成明显的冷点区域。水环境潜在污染高风险区集中分布在龙马潭区江段和江阳区江段,须提高该区域对潜在污染的风险管理能力,以降低污染事故发生的可能性。     

The use of polymerase chain reaction for the identification of sciaenid eggs

Traditionally, sciaenid eggs have been identified based on morphological characteristics such as size, number of oil globules and/or pigmentation patterns. Identification of sciaenid eggs by these procedures is time consuming and often inaccurate due to considerable egg size overlap among species. The utilization of molecular techniques for the identification of economically important species has become a fundamental component in ecological studies involving fish eggs and larvae. This study reports the development of a series of both multiplex and individual polymerase chain reactions to identify the eggs of 11 sciaenid species commonly found in the Gulf of Mexico and estuaries near Port Aransas and Corpus Christi, TX, USA. Following method development, the discriminatory power of the assay was first determined with samples from adult fish collected from Aransas and Corpus Christi Bays, Galveston Bay and the lower Laguna Madre in northern Mexico. Most (97%) of these fishes were correctly identified to the level of species. To demonstrate the applicability of the assay, wild fish eggs were collected and analyzed from the Aransas Pass tidal inlet from September through December 2005. During this period, the eggs of four target species were positively identified which was in keeping with current knowledge regarding the spawning areas and seasons of these sciaenids based on the presence of mature females, eggs and/or larvae. Future use of this method can provide valuable information to better discriminate spawning sites and seasons of these species.     

Comparative persistence of marine fish larvae from pelagic versus demersal eggs off southwestern Nova Scotia,Canada

Two groupings of larval fish were repeatedly identified by principal component analyses of larval densities from four broad-scale surveys during the spring and summer of 1985–1987 off southwestern Nova Scotia, Canada. Larvae originating from pelagic eggs (four species within Gadidae and Pleuronectidae) constituted one group, which were uniformly distributed over the sampling area with densities not correlated with bathymetry, although nearly all spawning occurs on the shallow western cap of Browns Bank, 100 km offshore. Larvae from demersal eggs (five species within Pholidae, Stichaeidae, Cottidae, Agonidae) constituted the second group, which dominated the shallow-water environments both inshore and on Browns Bank. Lower patchiness indices were evident amongst larvae from pelagic eggs in small and large sampling-gear collections (average 3.4 and 3.1, respectively) compared to fish hatching from demersal eggs (average 5.1 and 4.6). Fine-scale nearshore surveys over a 5 wk period in 1987 also showed that larvae of demersal eggs had a less variable distribution along an inshoreoffshore transect. Larvae from demersal eggs appear spatially persistent through the release of well-developed larvae from non-drifting eggs. These conclusions are consistent with other studies over a range of spatial scales in temperate and tropical environments, demonstrating that single-species models of larval dispersal are inadequate to account for the distributional patterns of larval fish in general.     

Underlying causes of habitat-associated differences in size of age-0 walleye pollock (Theragra chalcogramma) in the Gulf of Alaska

Age-0 walleye pollock (Theragra chalcogramma) caught in September in the Gulf of Alaska display habitat-associated differences in standard length (SL). Age-0 fish collected in the region around Sutwik Island and 375?km farther downstream near the Shumagin Islands most likely originate from the Shelikof Strait spawning aggregation. However, age-0 fish resulting from the same spawning aggregation differ in mean size up to 20?mm between areas by September. We examined the otoliths of the larval and age-0 stages of walleye pollock from these two areas in 2000 and 2001 to determine whether growth rate, hatch date, and/or temperature influenced fish size. Circulation models were used to determine whether transport of larvae from an upstream spawning group into the study areas could have occurred. Mean in situ temperature during sampling periods was not defined as a significant factor in altering growth rates. Overlapping hatch date distributions of the larval and age-0 fish in the Shumagin Island area confirmed that the fish were from the Shelikof Strait spawning group. Comparison of hatch date distributions in the upstream Sutwik Island area revealed larger/older larvae from an upstream spawning group mixed with larvae from the Shelikof Strait spawning group. Our results suggest that the offset of 20?mm SL between the groups of age-0 pollock was the result of a combination of enhanced survivorship of early-hatched larvae in the Sutwik area and the introduction and retention of the progeny of another spawning group originating upstream of Shelikof Strait.     

Hydrography and distribution dynamics of larval and juvenile fishes in the coastal waters of the Tanshui River estuary,Taiwan, with reference to estuarine larval transport

Distribution dynamics of fish larvae and juveniles in the coastal waters of the Tanshui River, Taiwan was studied fortnightly using surface horizontal tows with a larval net in daytime during the period from early April through early June 1991. Environmental factors, including water temperature, salinity, dissolved oxygen, pH, transparency and depth at sampling stations, were also monitored. A total of 10737 fish eggs and 1387 individuals, representing 43 families and 93 species, was collected during five cruises from 12 stations in the coastal waters. Most fish were estuarine-dependent marine species. Liza macrolepis, Ambassis gymnocephalus, Terapon jarbua, Mullidae and Gobiidae were the most dominant, making up 64.7% of the total catch. Early life stages, including egg, preflexion, flexion and postflexion larvae were abundant in surface samples. However, yolk-sac larvae were absent in the surface water, probably due to an ontogenetic behavioral shift as a consequence of a change in specific weight during early development. The species composition of fish larvae and juveniles was related to the microhabitats found in the coastal waters. The physico-chemical conditions, along with ontogenetic behavior, played an important role in larval fish distribution in the coastal waters.     

Shift of Spawning Season and Effects of Climate Warming on Developmental Stages of a Grayling (Salmonidae)

Abstract: River‐dwelling fish, such as European graylings (Thymallus thymallus), are susceptible to changes in climate because they can often not avoid suboptimal temperatures, especially during early developmental stages. We analyzed data collected in a 62‐year‐long (1948–2009) population monitoring program. Male and female graylings were sampled about three times/week during the yearly spawning season in order to follow the development of the population. The occurrence of females bearing ripe eggs was used to approximate the timing of each spawning season. In the last years of the study, spawning season was more than 3 weeks earlier than in the first years. This shift was linked to increasing water temperatures as recorded over the last 39 years with a temperature logger at the spawning site. In early spring water temperatures rose more slowly than in later spring. Thus, embryos and larvae were exposed to increasingly colder water at a stage that is critical for sex determination and pathogen resistance in other salmonids. In summer, however, fry were exposed to increasingly warmer temperatures. The changes in water temperatures that we found embryos, larvae, and fry were exposed to could be contributing to the decline in abundance that has occurred over the last 30–40 years.     

Food and feeding dynamics of the larval Antarctic fishNototheniops larseni

The feeding dynamics of larvae of the Antarctic fishNototheniops larseni were analyzed from data collected over three years in Bransfield Strait and adjacent waters (Antarctica). Seasonal feeding was examined from 1977/1978 (November–March). The diel feeding cycle was investigated during a 96 h station established in February 1976, while food selection was analyzed using larvae and zooplankton samples collected in February 1982. Hatching occurs in early spring, and larvae fed on eggs of calanoid copepods and on cyclopoid copepods. Copepod eggs were the principal food near the pack ice, and cyclopoids in open waters. Cyclopoids were the staple food in summer. Eggs of the Antarctic krillEuphausia superba were ingested selectively and formed major portions of the larval summer diet in neritic (Joinville Island) and oceanic (Elephant Island) spawning areas ofE. superba. In the fall, copepods predominated in the diets. Most abundant and most frequently ingested prey in summer and fall wereOncaea spp. Feeding commenced at dawn and continued at least until dusk. Krill eggs were taken chiefly during morning hours and egg incidence declined during the day, suggesting that eggs were ingested soon after spawning. Prey size at the onset of feeding was estimated as 0.130 to 0.330 mm. Size-selective feeding was evident in small larvae, while in larger larvae median prey length remained constant. High feeding incidence among yolk-sac larvae in spring, high overall feeding incidence in summer, and size-selective foraging of small larvae suggested favorable feeding conditions in the 1977/1978 season. Yolk-absorption times in Antarctic fish larvae vary on a scale of weeks and may be further retarded due to early feeding. Hence, year-to-year variability of yolk incidence inN. larseni indicated variable biotic environments of early feeding larvae rather than temporal shifts of hatching periods. As hatching periods are constant between years in contrast to the variable retreat of the pack ice and subsequent onset of the production cycle in space and time, maternal yolk reserves are probably utilized to compensate for such variations.     

Lipids and fatty acids as indicators of egg condition,larval feeding and maternal effects in Cape hakes (<Emphasis Type="Italic">Merluccius paradoxus</Emphasis> and <Emphasis Type="Italic">M. capensis</Emphasis>)

Cape hakes, Merluccius paradoxus and M. capensis, are important gadoid fish that are commercially harvested in the Benguela Current system off Namibia and South Africa. The aim of this study was to elucidate the nutritional condition and feeding preferences of their larvae. Hake eggs and larvae were sampled in austral spring of two consecutive years, 2007 and 2008, off the west coast of South Africa. They were identified to species using genetics, and total lipid content and fatty acid (FA) composition were analysed for each individual egg and larva to compare the condition of different early life stages of both hake species. Higher abundances of M. paradoxus eggs and larvae were consistently found compared to M. capensis. In both species, eggs contained wax esters (WE) and had significantly higher lipid content per dry mass than larvae. Lipid content as well as FA composition changed with the developmental stage of larvae. Quantities of essential fatty acid (EFA) increased with feeding of larvae due to dietary lipid incorporation. In 2007, yolk-sac larvae contained significantly lower total lipids than in 2008. It is argued that this was due to reduced lipid transfer by the spawning females to the eggs. These findings indicate that maternal effects are important in determining condition of hake larvae and that this may have an effect on their survival and subsequent recruitment.     

Larval fish assemblages in Independencia Bay,Pisco, Peru: temporal and spatial relationships

The structure of the larval fish assemblages in Independencia Bay on the coast of Peru was examined using a combination of univariate and multivariate techniques. The plankton of Independencia Bay was sampled during 2000, to ascertain ichthyoplankton composition, abundance, and seasonality. These data were used to assess the function of the bay as spawning and nursery grounds and were related to the regional oceanography. In total, 16,156 fish larvae, representing 34 families, 48 genera, and 48 species were collected. Engraulidae, Normanichthyidae, Blenniidae, Gobiesocidae, Haemulidae, Labrisomidae, Pinguipedidae, and Atherinidae comprised 96.8% of the larvae captured; the remaining 3.2% included 26 families. Greatest mean larval fish densities, 319–1,381 per 100 m³, were recorded between September and November, suggesting a major spring spawning period. The most abundant fish larvae during this period were preflexion stage mote sculpins (Normanichthyidae) and newly hatched and preflexion stage anchovies (Engraulidae). A second, smaller summer peak was dominated by preflexion stage anchovies, followed by preflexion stage mote sculpins. The occurrence of high larval fish densities and the wide range of larval stages suggest that Independencia Bay is a regionally important spawning and nursery ground for marine fish. The principal component analysis showed that temperature and salinity were the dominant variables within the first two principal components, which accounted for 74.4% of the variation in environmental conditions. These conditions varied over time, station, and depth; however, interaction terms could not clearly be identified. Fitting a multinomial logistic model showed that larval fish assemblages and environmental conditions were associated in a complex way. The spring and summer ichthyoplankton abundance peaks in Independencia Bay coincided with high zooplankton standing stock and also coincided approximately with the periods of increased upwelling in the area.Communicated by O. Kinne, Oldendorf/Luhe     

Lipid and protein utilisation during early development of yellowtail kingfish (<Emphasis Type="Italic">Seriola lalandi</Emphasis>)

The pelagic yellowtail kingfish Seriola lalandi has become a target species for aquaculture in Asia and Australasia. Australasian production is reliant on larviculture from eggs of captive brood stock; however, knowledge regarding the nutritional requirements of larvae of this species is still scarce, particularly in relation to lipids. As a first step in establishing these requirements, eggs and larvae from captive S. lalandi brood stock were examined for differences in total protein, total lipid and lipid classes between individual spawning events, over the spawning season, and during larval development from fertilisation to 15 days post hatch. Results indicate that total protein egg⁻¹ varied significantly between individual spawning events within a season, but neither total lipid nor total protein egg⁻¹ varied significantly across the spawning season. Brood stock egg lipids were made up of approximately 60% phospholipid, 25% wax and/or sterol esters (WE), 15% triacylglycerol (TAG), and small amounts of sterols and free fatty acids. During the early larval period, both WE and TAG were utilised concurrently for energy. The larvae experienced very high mortality around 5–7 days post hatch, which coincided with very low levels of all neutral lipid classes. Although many other factors may also influence larval mortality, these results indicate that lipid provisioning may be an important factor in larval survival during the critical period around first-feeding in this species. Examination of ratios of TAG:ST, often used as a condition index in fish larvae, suggested that some of the larvae were suffering from starvation. However, as egg-derived WE appears to provide a significant source of energy during the early larval period in S. lalandi, it is suggested that WE should be included in any index of larval nutritional state.     

Nearshore distributional gradients of larval fish (15 taxa) and planktonic crustaceans (6 Taxa) in Hawaii

Fifteen taxa of fish larvae (most identified to species) and 6 taxa of crustaceans (most identified to species) were studied in zooplankton samples collected 0.2, 0.5, 1.0 and 3.0 km off the leeward coast of Oahu, Hawaii in May and July 1975. The following distributional patterns were elucidated: inshore (2 spp); inshore-neritic (2 spp); neritic (7 spp); and offshore-neritic (7 spp). Three of these 18 species had age-related differences in behaviour that led to age-dependent distributional patterns, and 4 further species had a random distribution. All abundant types of fish larvae were either oceanic as adults or were hatches from the demersal or brooded eggs of reef species. The larvae of reef fishes with pelagic eggs were not abundant in the nearshore region sampled and were probably to be found more than 3 km offshore. The offshore-neritic distributional pattern evidently resulted from relatively passive movement with currents. In contrast, maintenance of inshore and neritic patterns probably required relatively active swimming by the animals. The current regime, including a tidal eddy and possible nearshore upwelling, probably helped maintain the inshore and neritic patterns of such animals. The limited area occupied by these inshore coastal plankton communities could make them particularly vulnerable to environmental changes, including anthrogenic ones.