Artificial daily fluctuations of river discharge affect the larval drift and survival of a tropical amphidromous goby

Amphidromous fish species reproduce in rivers, and their larvae immediately drift to the sea after hatching. Most of these larvae survive in freshwater for a few days only, rapidly reaching sea water is thus essential. Being of small size, especially among species of the Sicydiinae subfamily, the larvae possess poor swimming abilities; their drift dynamics is considered to be mainly passive and influenced by flow conditions. The influence of daily fluctuations in flow regime on Sicyopterus lagocephalus (Sicydiinae) larval drift patterns was studied using drift nets at three sites along the dammed Langevin River in Reunion Island. The river flow was stable at the upstream site when frequent anthropogenic river flow fluctuations were observed at the two sites downstream to the dam. Weak diel larval drift dynamics were detected at the upstream site and the first site under anthropogenic river flow conditions. In contrast, larval drift dynamics at the most downstream site was strongly influenced by anthropogenic daily fluctuations of discharge: the abundance of drifting larvae increased with peaks of discharge, regardless of the time. As higher mortality rates of drifting larvae were observed during discharge peaks, the benefit of a more rapid travel to the ocean associated with these peaks should be lower than expected. It is concluded that peaks of discharge increase the number of larvae drifting to the sea probably due to higher physical constraints on the egg clutches, but also decrease the chance of survival for larvae that may be nonfully developed.     

Insights on endemism: comparison of the duration of the marine larval phase estimated by otolith microstructural analysis of three amphidromous Sicyopterus species (Gobioidei: Sicydiinae) from Vanuatu and New Caledonia

Lord C, Brun C, Hautecœur M, Keith P. Insights on endemism: comparison of the duration of the marine larval phase estimated by otolith microstructural analysis of three amphidromous Sicyopterus species (Gobioidei: Sicydiinae) from Vanuatu and New Caledonia.
Ecology of Freshwater Fish 2010: 19: 26–38. © 2009 John Wiley & Sons A/S
Abstract –  The microstructure of otoliths of three amphidromous gobies (Sicydiinae) of the genus Sicyopterus has been analysed. One of these species, Sicyopterus lagocephalus has a widespread distribution whereas the other two are endemic ( Sicyopterus aiensis , from Vanuatu and Sicyopterus sarasini , from New Caledonia). The microstructural analysis of the otoliths showed that the duration of the marine larval phase is significantly shorter for both endemic species than for the cosmopolitan species (131 ± 3.4 days for S. lagocephalus , 79.2 ± 4.6 days for S. aiensis and 76.5 ± 3.9 days for S. sarasini ). These results led us to infer that it could be one of the factors explaining endemism. We have also improved our knowledge on the processes undergone during the marine phase by studying the growth of the otolith. This work allowed us to propose possible migration routes. These species' reproduction period has also been studied by back-calculating hatching dates. All these elements improve our understanding of the life-history traits and dispersion strategies of these species, which is crucial to implementing conservation measures in order to protect them and their environment, both threatened by anthropogenic actions.     

Growth and age at first maturity in turbot and halibut reared under different photoperiods

The effect of extended photoperiods on growth and age at first maturity was investigated in 166 (79 females and 87 males) individually tagged Atlantic halibut Hippoglossus hippoglossus and in 114 (50 females and 64 males) individually tagged turbot Scophthalmus maximus. The halibut were reared at 11 °C on four different light regimes from 10 February to 6 July 1996: simulated natural photoperiod, (LDN), continuous light (LD24:0), constant 8 h light and 16 h darkness (LD8:16) and LD8:16 switched to continuous light 4 May 1996 (LD8:16–24:0). From 6 July 1996 to 9 February 1998 the LD24:0 and LD8:16–24:0 were reared together under continuous light and the LDN and LD8:16 together under natural photoperiod. The turbot were reared at 16 °C on three different light regimes: constant light (LD24:0), 16 h light:8 h darkness (LD16:8), or simulated natural photoperiod (LDN). After 6 months on the different photoperiods, the turbot was reared together on LDN for approximately 12 months until first maturation. Juveniles subjected to continuous light (halibut) or extended photoperiods (halibut and turbot) exhibited faster growth than those experiencing a natural photoperiod or a constant short day. Moreover, when the photoperiod increased naturally with day-length or when fish were abruptly switched from being reared on short-day conditions to continuous light, a subsequent increase in growth rate was observed. This growth enhancing effect of extended photoperiods was more apparent on a short time scale in Atlantic halibut than in turbot, but both species show significant long-term effects of extended photoperiods in the form of enhanced growth. In both species lower maturation of males was seen in groups exposed to extended or continuous light compared to LDN and this could be used to reduce precocious maturation in males leading to overall increase in somatic growth. This revised version was published online in August 2006 with corrections to the Cover Date.     

Chronological age and reservoir characteristics as predictors of trait composition in Neotropical reservoir fish assemblages

One of the main impacts on aquatic environments is the alteration of flow regime, usually caused by dam construction. This impact changes the dynamics and functioning of the environment. We aimed to evaluate changes in the composition of functional traits of fish assemblages from 29 reservoirs of different chronological ages. We assessed if there were any alterations in trophic state of these reservoirs according to their ages (chronological variable). Then, we evaluated the relationship between functional traits and environmental/chronological variables. Results showed that reservoir age is a predictor of fish assemblage functional traits composition. In older reservoirs, there was a predominance of omnivorous species, with multiple spawning and parental care. However, herbivorous species, with total spawning and medium size, had their abundance reduced. Also, it was possible to identify the influence of depth and water retention time on the composition of functional traits. By showing that although age has an influence on composition, the intrinsic characteristics of each reservoir are very important in evaluating the impacts of these projects. Therefore, the findings presented provide insights into what may happen to functional traits of fish assemblages with ageing of reservoirs.     

象山港春、夏季仔稚鱼种类组成结构特征

为研究象山港仔稚鱼的时空分布特征及其与环境因子的相关关系,在象山港港湾内设置14个站,于2015年4月3日~6月10日期间按周采样,共调查10个航次(Ⅰ~Ⅹ),用方形网(网口为1 m×2 m,网目1.0 mm)采集仔稚鱼,同时采集温度、盐度和浮游动物等数据。调查期间采集仔稚鱼180 254 ind共45种,隶属25科39属,主要优势种为斑鰶(Konosirus punctatus)、矛尾鰕虎鱼(Chaeturichthys stigmatias)、鮻(Chelon haematocheilus)、斑尾刺鰕虎鱼(Acanthogobius ommaturus)、普氏缰鰕虎鱼(Amoya pflaumi)、拟矛尾鰕虎鱼(Parachaeturichthys polynema)、黑棘鲷(Acanthopagrus schlegelii)、舌鰕虎鱼(Glossogobius giuris)等。仔稚鱼密度呈先升后降的趋势,第Ⅲ航次密度最高(平均密度为587.9 ind·100 m-3),第Ⅷ航次最低(8.2 ind·100m-3)。前弯曲期仔鱼最多,占63.6%,弯曲期仔鱼占26.4%。基于层级聚类(Bray-Curtis相似性指数,Ward法聚类)分析表明,可将10航次仔稚鱼分为4个类型,各类型间存在明显差异:类型1(Ⅰ和Ⅱ航次)主要为矛尾鰕虎鱼和斑尾刺鰕虎鱼,类型2(Ⅲ~Ⅵ航次)为斑鰶、鮻、矛尾鰕虎鱼和黑棘鲷,类型3(Ⅶ和Ⅷ航次)为斑鰶、日本鳀(Engraulis japonicus)、拟矛尾鰕虎鱼,类型4(Ⅸ和Ⅹ航次)为普氏缰鰕虎鱼、拟矛尾鰕虎鱼、美肩鳃鳚(Omobranchus elegans)。Spearman相关分析表明,仔稚鱼分布与温度极显著相关(P0.01),与浮游动物密度呈显著相关(P0.05),与盐度无明显相关关系(P0.05)。     

Egg and larval distributions of seven fish species in north-east Atlantic waters

The distribution of egg and larvae of mackerel, horse mackerel, sardine, hake, megrim, blue whiting and anchovy along the European Atlantic waters (south Portugal to Scotland) during 1998 is described. Time of the year, sea surface temperature and bottom depth are used to define the spawning habitat of the different species. Mackerel, horse mackerel, and sardine eggs and larvae presented the widest distribution, whereas megrim and anchovy showed a limited distribution, restricted to the Celtic Sea and the Bay of Biscay respectively. Correspondingly mackerel, horse mackerel and sardine showed the highest aggregation indices. Blue whiting larvae were found at the lowest temperatures, whereas anchovy eggs and larvae were found in the warmest waters. The analysis is a basis for evaluation of ongoing changes in the pelagic ecosystem of the north‐east Atlantic.     

Pelagic larval duration of three amphidromous Sicydiinae gobies (Teleostei: Gobioidei) including widespread and endemic species

Sicydiinae species have an amphidromous life cycle during which they undergo a pelagic larval phase allowing them to disperse through the ocean and to recruit in distant island rivers. Hypotheses for the differences observed in dispersal abilities between species include the variation in pelagic larval duration (PLD). However, the implication of the PLD as a proxy for explaining the dispersal ability of a species is not clear in the Sicydiinae subfamily. In this study, otolith microstructure of three Sicydiinae species was analysed. One of these species, Sicyopus zosterophorum, has a widespread distribution in the West Pacific area, whereas the other two species, Smilosicyopus chloe and Akihito vanuatu, are endemic to New Caledonia and to Vanuatu, respectively. Deposition of the daily growth increments on the otoliths of S. zosterophorum was validated using an alizarin complexone time marking technique. We estimated the PLD for the three species by counting the number of growth increments from the core to the metamorphosis check mark, and it was shorter than the one of previous studies on Sicydiinae species. The PLD of the widespread species, S. zosterophorum (54.6 ± 5.6 days), was similar to those of the endemic species, S. chloe (53.6 ± 5.7 days) and A. vanuatu (55.4 ± 7.5 days). Here, we show that in contrast to the most diverse Sicydiinae genus, Sicyopterus, the PLD could not explain endemism, and we must take into account other elements to explain the differences observed in the distribution range.     

Predation effects on matrotrophy,superfetation and other life history traits in Phalloceros harpagos

This study investigates the effect of a predation gradient on the female life history traits of the poeciliid live‐bearing fish Phalloceros harpagos from a tropical stream in Brazil. Females’ length at maturity, somatic dry mass, reproductive allotment and fecundity varied significantly among predation sites. Phalloceros harpagos from the high‐predation site showed smaller size at maturity and somatic dry mass, greater reproductive allotment and higher fecundity than the nonpredation site. In all sites, we observed superfetation: pregnant females with two broods at different developmental stages. The presence of superfetation was not observed before in other congeneric species, and it may represent an additional independent evolutionary origin of superfetation in the fish family Poeciliidae. Matrotrophy, the postfertilisation maternal provisioning of nutrients to developing embryos throughout gestation, was observed in all three sites, with values of the matrotrophy index above two. The population under high predation pressure showed the highest degree of matrotrophy (embryos quadruplicate their dry mass during development) and the greatest percentage of females with superfetation (44.4%). Some life history traits responded more strongly to predators’ presence and others to predator density. These results suggest that different predation regimes shape female life history traits, increasing fecundity in high‐predation sites. The results also suggest a link between the cost of reproduction and the evolution of matrotrophy and superfetation, potentially to reduce the risk of predation without reducing fecundity.     

鱼体脂肪、蛋白质含量的季节变化对鱼类生活史的影响

鱼体脂肪、蛋白质含量的季节变化是鱼类生物学的一个重要特征,它与洄游、性腺发育、繁殖力、体长等都具有密切的关系,反映了鱼类生活史的不同阶段变化过程.本文根据国内外对鱼类脂肪、蛋白质含量的研究资料,初步阐述了脂肪、蛋白质含量在鱼类洄游、性腺发育、繁殖力等方面所起的作用及机理,指出了研究鱼类能量学对于更好了解鱼类的生物学特征、鱼产品加工业以及制订渔业管理措施等具有重要的意义.     

Antibacterial abilities of intestinal bacteria from larval and juvenile Japanese flounder against fish pathogens

The present study was undertaken to examine the antibacterial abilities of intestinal bacteria isolated from juveniles and larvae of Japanese flounder Paralichthys olivaceus . Newly hatched larvae of flounder were held in a 100 L plastic circular tank and fed rotifiers, Artemia nauplii and commercial feeds, depending on the developmental stage of the fish. Genera Aeromonas , Moraxella and Vibrio were predominantly isolated from the intestinal tracts of Japanese flounder at larval and juvenile stages, whereas Aeromonas , Bacillus , coryneforms, Moraxella , Pseudomonas and Vibrio were detected at high densities in live diets and artificial feeds. Antibacterial bacteria accounted for 1.7–24.3% of the intestinal isolates against Lactococcus garvieae , Pasteurella piscicida , Vibrio anguillarum and V. vulnificus . In particular, as much as 53.3% of Vibrio spp. other than Vibrio -swarmer isolated from 197-day-old juveniles inhibited the growth of P. piscicida . These results suggest that intestinal bacteria having antibacterial activity play a role in the prevention of infectious diseases.     

The relation between age at first maturity and growth in Atlantic halibut (Hippoglossus hippoglossus) reared at four different light regimes

The effect of extended photoperiods on growth and age at first maturity was investigated in 166 (79 females and 87 males) individually tagged Atlantic halibut. The halibut were reared at 11°C on four different light regimes from 10 February to 6 July 1996: simulated natural photoperiod, (LDN), continuous light (LD24:0), constant 8 h light and 16 h darkness (LD8:16) and LD8:16 switched to continuous light on 4 May 1996 (LD8:16–24:0). From 6 July 1996 to 9 February 1998 the LD24:0 and LD8:16–24:0 were reared together under continuous light and the LDN and LD8:16 together under natural photoperiod. Juveniles subjected to continuous light exhibited faster growth than those experiencing a natural photoperiod or a constant short day. Moreover, the results suggest an overall growth enhancing effect of continuous light in females, but not in males. No females matured during the trial, but the proportion of mature males differed between the photoperiod groups, with significantly fewer males maturing in groups reared at continuous light. Independent of photoperiod regime and maturation status, females were significantly bigger than males from 14 April 1997 onwards. Immature males were bigger than maturing males from 23 March 1996 onwards. As continuous light reduced maturation at age 2+ in males, this could be used to reduce precocious maturation in males.     

大弹涂鱼仔稚鱼和早期幼鱼的消化酶活性

采用酶学分析的方法,研究了大弹涂鱼前期仔鱼、后期仔鱼、稚鱼和早期幼鱼发育过程中胰腺酶、肠酶和胃蛋白酶活性的变化。结果表明,(1)4种胰腺酶(淀粉酶、胰蛋白酶、糜蛋白酶和羧肽酶A)和8种肠酶(麦芽糖酶、蔗糖酶、乳糖酶、海藻糖酶、纤维二糖酶、碱性磷酸酶、氨基肽酶和γ-谷氨酰转肽酶)的比活力均在仔鱼期较高,稚鱼期降至最低,早期幼鱼则急剧上升,而每尾鱼酶的总活力却随着幼体的发育而逐渐增加;(2)胃蛋白酶活性在后期仔鱼才开始检测到,此后一直呈显著上升趋势;(3)早期幼鱼肠部位的4种胰腺酶活性分别占其酶总活性的百分比均显著高于稚鱼期;(4) 稚鱼期仅3种肠酶(麦芽糖酶、纤维二糖酶和γ-谷氨酰转肽酶)高度富积在肠刷状缘膜上,而早期幼鱼除蔗糖酶外的7种肠酶在肠刷状缘膜上的富集系数均大于5.1。由此得出结论,(1)在仔鱼期,蛋白质的消化是依靠胰腺酶进行的,进入稚鱼期,胃蛋白酶开始对蛋白质的消化起重要作用;(2)在早期幼鱼,胰腺分泌机制及肠细胞已完全成熟,标志着成鱼的消化模式的形成。     

The utility of otolith weight as a predictor of age in the emperor Lethrinus mahsena and other tropical fish species

This study examines the potential use of otolith weight as a proxy for age in the lethrinid Lethrinus mahsena from different sites in the tropical Indian Ocean: the banks of Seychelles, Mauritius and British Indian Ocean Territory (BIOT, Chagos Archipelago). The reliability of age–frequency distributions and individual ages estimated using otolith weight–age relationships was examined through comparison with those estimated through the standard method of ageing using otolith increments. Two other methods for estimating age–frequencies using age-slicing via an estimated growth curve were also examined; these used growth curves estimated by a length-based method (ELEFAN), or by fitting directly to length-at-age data (an ‘age-based’ method). Age-slicing using length-based growth parameters failed to produce reliable age–frequencies, due to inaccuracies in the growth parameter estimates. The use of age-based growth parameter estimates improved the results of age-slicing, however, age–frequencies remained significantly different from those obtained from ageing using otolith increments in two locations. The use of otolith weight–age relationships resulted in estimated age–frequency distributions that in all locations were not significantly different from those assessed through otolith increment counts. In contrast, L. mahsena otolith weight–age relationships could not be used to estimate individual ages accurately, due to the level of overlap in otolith weight between age classes. Where otolith increments are routinely used to age commercial fish species, the fact that otolith weight–age relationships could not be used to age individuals accurately may limit its application. However, where routine ageing of individuals through otolith increments is considered impractical, for instance because of its cost, the use of otolith weight–age relationships to derive catch age–frequencies represents a viable alternative approach. With this in mind, this study has also demonstrated that there is the potential to use otolith weight–age relationships for five other species caught around the Seychelles, following the validation of their otolith increments.     

Congruence between riverine fish species richness and endemism at the biogeographical scale: the role of history

• 1. This study aims to illustrate, on a European scale, how the congruence between riverine fish species richness and endemism is strongly related to biogeographical history.
• 2. A positive curvilinear relationship between species richness and endemism was found for Ponto‐Caspian Europe and peri‐Mediterranea, both spared by the last glacial maximum.
• 3. These results have important implications for European riverine fish biodiversity conservation, notably with regard to peri‐Mediterranea, which is expected to suffer from major climatic changes during the 21st century.

Copyright © 2008 John Wiley & Sons, Ltd.     

Interactive effects of life history and season on size‐dependent growth in juvenile Atlantic salmon

Size‐dependent growth (SDG) is an important process in structuring populations as well as determining life history outcomes. Despite its importance, there have been few investigations from observational studies focusing on the interaction between life history decisions and SDG. In this study, we used data on individually tagged Atlantic salmon from both the laboratory and the field to investigate differences in SDG among two life history groups, parr and smolts. In the laboratory, we found little evidence of SDG in parr but seasonally dependent SDG in the smolt group. Smolts showed at strong compensatory response over the winter months just prior to the smolt transformation window. In the field, we found little evidence of SDG early in ontogeny (i.e., age 0+ fall and winter). There was some evidence of depensatory growth (positive SDG) during the age 1+ spring among both life history groups that may reflect random habitat variation or the monopolisation of resources. After the age 1+ spring, we found that smolts were more likely to show a compensatory effect (negative SDG) than parr. This effect was strongest, as they approached the smolt window in the spring of their age 2+ year. These results suggest (i) SDG is common in Atlantic salmon; however, the form and extent of life history depends on (ii) season and (iii) life history. For individuals that adopt a smolt life history, trade‐offs between freshwater survival and sea survival may lead to a convergent growth pattern, as they approach the smolt migration window.     

Distribution patterns of larval myctophid fish assemblages in the subtropical–tropical waters of the western North Pacific

We examined larval myctophid fish assemblages and their distribution patterns, based on discrete depth sampling. Samples were collected at 19 stations along a transect that crossed the subtropical–tropical waters of the western North Pacific. In total, we collected 27 189 larvae of 40 myctophid species or types, belonging to 15 genera. Three assemblages were recognized, based on their species composition: Kuroshio Axis (KuA), Kuroshio Countercurrent (KCC), and Subtropical Countercurrent–North Equatorial Current (SCC–NEC) assemblages. The distributions of these assemblages were well defined by the positions of the KuA and the Subtropical Convergence. Each species had a specific distribution depth, and none showed diel vertical migration. Larvae of the subfamily Lampanyctinae were distributed in shallower waters (0–50 m) than larvae of the subfamily Myctophinae (50–150 m). Larvae of the same species were distributed at lower depths in the SCC–NEC area than in the KCC area. This corresponded to the abundance of chlorophyll a, which would reflect abundance of prey organisms such as copepod nauplii and copepodites.     

Influence of tropical seasonal changes on oocyte diameter, responses to hormonal induction and hatching quality in two strains of the catfish, Heterobranchus longifilis Val. (Clariidae)

A comparison was made between the oocyte diameter, pseudo‐absolute fecundity (PAF) and egg quality of two strains of the catfish, Heterobranchus longifilis, maintained in outdoor ponds under a tropical highland climate in Cameroon. The results indicated that circannual endogenous rhythms for ovarian recrudescence and regression are absent in H. longifilis, irrespective of breeding history, age and strain. There appeared to be a possible slight adverse effect of climate (dry season) on reproductive performance of both strains. Oocyte diameter and PAF increased with increasing fish weight when data from both strains were combined, indicating that the two strains may exhibit the same reproductive performance. Viable eggs were obtained all year round after hormonal induction. It is concluded that for propagation of H. longifilis in tropical African countries, broodfish could be maintained in outdoor earthen fish ponds with proper feeding.     

斑点鳟仔、稚、幼鱼的形态发育

以斑点鳟(Oncorhynchus mykiss)发眼卵为材料,进行了发眼卵的人工孵化及仔鱼的人工培育研究。对斑点鳟仔稚鱼的形态发育进行了系统观察,描述了各发育期的形态特征,并测定生长参数。斑点鳟早期生活史的分期如下:初孵仔鱼全长14.25±0.45 mm,体重85±5 mg,肛门未开口,营内源性营养,脊柱末端向上弯曲;10 dph开始上浮,投喂卤虫;12 dph开口摄食,开始营内外源混合性营养;14 dph鳍膜消失,各鳍独立;16dph开始投喂配合饵料;24 dph卵黄囊吸收完毕,营完全外源性营养;34 dph,体侧形成8～9个幼鲑斑;44 dph各鳍的鳍条发育健全;60 dph幼鱼外形为纺锤形,与成鱼相同。研究表明,斑点鳟早期生长发育过程中全长、肛门前长、水平眼径和头高的生长情况基本相同,0～16 dph生长速度较快,16～44 dph生长速度较慢,44 dph后生长速度再次变快。     

The effect of dispersal and temperature on the early life history of a temperate marine fish

Understanding the mechanisms that influence the successful recruitment of marine species is one of the great challenges in marine science, particularly for species that undergo a protracted larval phase. Here we apply a bio‐physical individual‐based model (IBM) which couples data from a high‐resolution oceanographic model with temperature‐related survival characteristics for the early life stage of a temperate marine fish. The IBM was run retrospectively for the years 1993–2007 with spawning locations occurring around Tasmania, Australia. Meso‐scale oceanographic features led to individuals spawned on the west coast, and to a lesser extent the south coast, being washed ashore prior to achieving a competent size to actively influence their migratory paths. Individuals spawned on the east coast had significantly higher survival rates. Temperature‐induced mortality was relatively consistent across years. This indicates that the dispersal envelopes, of pre‐flexion larvae, across all years are predominately within the thermal niche of this species. To further understand the effect of temperature on survival we integrated global climate model warming scenarios into the model. The results indicated that around the year 2050 the predicted warming would have a minor positive effect on the survival of individuals but by 2100 the pejus temperature will frequently be exceeded leading to a significant decline in survival, particularly towards the northern end of the dispersal range.