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1.
Diadromous species of tropical islands face numerous anthropogenic disturbances. Understanding how these disturbances affect the population dynamic of these species is important to develop ecologically based management measures. The upstream migration dynamics of two amphidromous gobies, Sicyopterus lagocephalus (Pallas) and Cotylopus acutipinnis (Guichenot), was described using intensive fishway monitoring (28 sampling dates over 1.5 years, 13 000 S. lagocephalus, 23 000 C. acutipinnis captured). Migration peak occurred for both species during the afternoon at the end of austral winter/beginning of austral summer. Abundance and size of fish caught in the river showed a marked impact of a dam (six sampling dates approximately 4000 individuals of each species captured). This study provides critical data for better management of fishways used by tropical amphidromous gobies. It appears especially important to reduce unwanted rheotactic sources that attract the fish away from the fishway's entrance.  相似文献   

2.
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3.
All native fishes living in the Caribbean island rivers are considered diadromous but few species have been validated as diadromous. In Guadeloupe (Lesser Antilles) as well as in the other tropical islands, the riverine habitats are subject to strong anthropogenic pressure due to resource modifications or dams. The management of fish biodiversity requires knowledge concerning their life history traits and behaviour that are still unknown for most species at a local scale and at the whole distribution area of the species. In a Guadeloupe river, we inferred the migratory patterns of four freshwater fishes common to Caribbean rivers by the analysis of otolith microchemistry. We found two species Eleotris perniger (Eleotridae) and Sicydium plumieri (Gobiidae) to be completely amphidromous with a marine larval phase and a freshwater adult phase. Agonostomus monticola (Mugilidae) was also found to be amphidromous in this system. The fourth species Gobiesox cephalus (Gobiesocidae) showed elemental ratios suggesting an estuarine larval phase and was defined as “limited amphidromous”. The identification of such life history traits, with limited dispersion abilities, argues for specific management measures in tropical island rivers at a basin scale for the conservation of biodiversity.  相似文献   

4.
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.  相似文献   

5.
Amphidromous fish are the biggest contributor to the diversity of fish communities in river systems of Caribbean islands. Among them, Sicydium punctatum Perugia, 1896, which is endemic to the West Indies, represents the vast majority of fish in these rivers. The otolith microstructure and the biometry of S. punctatum postlarvae from Guadeloupe were investigated to explore the dispersal modalities of this species through an appreciation of the growth pattern, the pelagic larval duration (PLD) and the size‐at‐recruitment. The study was made on one cohort of 83 recruited postlarvae, fished at the Capesterre River's mouth on 2 November 2011. The mean (±SD) size‐at‐recruitment of the postlarvae was 24.6 ± 1.3 mm (range of 20.5–28.1 mm, n = 83). We found a mean (±SD) PLD of 72.2 ± 10.5 days (range of 54–101.5 days, n = 67). The growth rate estimated from the otolith increments showed a globally decreasing pattern during the marine larval phase. Growth rates at the beginning of the larval stage were significantly different between hatching periods, suggesting a relation between the hatching period and the growth rate in S. punctatum. This study adds on to the general understanding of the life cycle of S. punctatum in Guadeloupe that will help implement strategies to manage amphidromous fish populations in the Caribbean region.  相似文献   

6.
Amphidromous gobies represent a substantial part of freshwater fish diversity throughout islands of the Indo‐Pacific region. They display a marine pelagic phase during several months before recruiting in rivers. Understanding the relationship between larval traits and environmental conditions is a major challenge for the evaluation of a spatial scale of connectivity and populations’ dynamics, especially in a climate change context. In this study, the larval traits of Sicyopterus lagocephalus were examined and related to the sea surface temperature (SST), over three consecutive years in La Réunion Island (Mascarene archipelago). The pelagic larval duration (PLD, range from 96 to 293 days), the size‐at‐recruitment (range from 26.5 to 37 mm TL) and the larval growth rate (range from 0.112 to 0.293 mm·day?1 TL) varied seasonally depending on hatching date. The larval growth rate was inversely correlated to the fluctuations of PLD and size. Larvae living in high sea water temperatures exhibited a faster growth, shorter PLDs and smaller sizes‐at‐recruitment than those living in cool water temperatures. The instantaneous daily growth was assessed by the study of otolith increment widths. The daily growth was not linear throughout larval life and was positively correlated to SST. We showed high amplitude of PLD periodic fluctuations (170.39 ± 43.75 days) related to temperature (12.8% PLD drop per degree), which could affect dispersal and induce intermittent connectivity between distant populations. This high plasticity of larval traits is likely to be advantageous to respond to the wide range of environmental conditions encountered throughout the species distribution range.  相似文献   

7.
Relationships between abundance of post‐larval and juvenile carangid (jacks) fishes and physical oceanographic conditions were examined in the northern Gulf of Mexico (GoM) in 2011 with high freshwater input from the Mississippi River. Generalized additive models (GAMs) were used to explore complex relationships between carangid abundance and physical oceanographic data of sea surface temperature (SST), sea surface height anomaly (SSHA) and salinity. The five most abundant carangid species collected were: Selene setapinnis (34%); Caranx crysos (30%); Caranx hippos (10%); Chloroscombrus chrysurus (9%) and Trachurus lathami (8%). Post‐larval carangids (median standard length [SL] = 10 mm) were less abundant during the spring and early summer, but more abundant during the late summer and fall, suggesting summer to fall spawning for most species. Juvenile carangid (median SL = 23 mm) abundance also increased between the mid‐summer and early fall. Most species showed increased abundance at lower salinities and higher temperatures, suggesting entrainment of post‐larval fishes or feeding aggregations of juveniles at frontal convergence zones between the expansive river plume and dynamic mesoscale eddy water masses. However, responses were species‐ and life‐stage specific, which may indicate fine‐scale habitat partitioning between species. Ordination methods also revealed higher carangid abundances at lower salinities for both post‐larval and juvenile life stages, with species‐ and life‐stage specific responses to SST and SSHA, further suggesting habitat separation between species. Results indicate strong links between physical oceanographic features and carangid distributions in the dynamic northern GoM.  相似文献   

8.
The widely distributed amphidromous goby Sicyopterus lagocephalus needs drastic change of habitat to fulfil its life cycle: adults live and spawn in rivers, where eggs hatch into prolarvae that have to reach the sea to acquire characteristics of planktonic larvae. Postlarvae return to rivers where they recruit and grow to the adult reproductive stage. Here, we describe the prolarval stages, namely from hatching to first contact with sea water, as well as the first marine larval stages. The observations were made under experimental conditions. We described 3 prolarval substages in freshwater (L1a–L1c). Prolarvae present a slight but visible ontogenetic development in freshwater, during which the yolk sac begins to reduce, the pigmentation increases on the body and in the eyes, and the lenses appear, although the eyes are not functional. Prolarvae need to reach the sea in a maximum of 96 h to pursue their development. Their transfer in sea water at a salinity of 36.5 induces important morphological modifications (i.e. yolk sac full absorption, appearance of pectoral fins, migration of the eyes in anterolateral position of the head, opening of mouth and anus), enabling the organisms to adapt to their new environment. This marine stage is divided into two substages: L2a corresponding to the organisation of the morphological structures adapted to the marine environment and L2b during which these morphological structures become functional. Whether it is in freshwater or sea water, the duration of the substages depends on the water temperature, but is similar for all individuals for a given temperature.  相似文献   

9.
Prochilodus lineatus (Val.) is one of the main target species of South American freshwater fisheries. The following null hypotheses regarding juvenile recruitment of P. lineatus were tested: (a) recruitment is not determined by variations in larval abundance and (b) recruitment is not determined by variations in discharge. For this purpose, variations in abundance of larvae in main channel drift and monthly captures of juveniles in a floodplain lake of the River Paraná were examined weekly between 2009 and 2016. Mean annual abundances of larval densities and CPUE of juveniles were correlated with a set of hydrometric variables. A positive correlation was found between the abundance of juveniles with high and persistent flood pulses. By contrast, larval abundance was not correlated with juvenile abundance. Pronounced contrast was found in the recruitment of P. lineatus between years of high and low discharge, which supports the hypothesis that floods are the main determining factor for recruitment of this species.  相似文献   

10.
  1. Rafting has been proposed as a dispersive mechanism for some species of seahorses. Juvenile Hippocampus patagonicus rafting on the sea surface have been reported. This life stage has high mortality in nature due to ecological and environmental factors usually affecting juvenile planktonic teleosts (e.g. predation).
  2. In this study, 50 juvenile seahorses were captured while rafting at the beginning of the reproductive season (December). They were grown out under a standard protocol in a recirculating aquaculture system for 120 days until they reached maturity.
  3. During this period, only three seahorses died (6%). Mature seahorses were 65 ± 7 mm average height and showed variable coloration and pigmentation pattern (n = 47; 94%).
  4. The availability of juvenile seahorses during the reproductive season and their high survival performance ex situ highlight the feasibility of developing protocols in which juvenile seahorses serve as a novel source of broodstock.
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12.
Migratory fishes can be threatened by conditions encountered along dispersal pathways that impede access to feeding or breeding grounds. In this study, we tested the hypothesis that amphidromous fishes are equally or more sensitive to conditions along dispersal pathways than conditions in primary residential habitats. We did so by conducting distribution‐wide population surveys of all five amphidromous gobies native to the Hawaiian Islands to assess responses to in‐stream habitat, invasive species and watershed land use. We used Redundancy Analyses to assess whether goby densities varied according to local, downstream or upstream conditions. We found that population densities of the two non‐climbing species (Eleotris sandwicensis, Stenogobius hawaiiensis) varied according to local land use and local habitat conditions. Greater densities of E. sandwicensis also were found in watersheds with greater forest cover upstream of survey sites. Lower densities of two species that migrate farther inland (Awaous stamineus, Sicyopterus stimpsoni) were observed in watersheds with greater anthropogenic land use downstream or at the stream mouth. Population densities of E. sandwicensis and both Sicydiine species (Lentipes concolor, S. stimpsoni) also were lower when non‐native Poeciliids were locally present or present downstream in the watershed. These findings suggest that densities of native Hawaiian amphidromous fishes are equally or more sensitive to conditions along migratory pathways relative to conditions in primary residential habitats. Thus, alleviating pressures by removing invasive species and restoring habitat along dispersal pathways could be effective approaches to increasing densities of amphidromous species, especially those that migrate farther inland to higher elevations.  相似文献   

13.
The pelagic larval duration (PLD) period of fish can influence dispersal, recruitment, and population connectivity, thereby potentially informing best strategies for fisheries management. Computer models were used to simulate the dispersal of larvae of three species, representing a range of PLDs, from the Pacific island of Guam and neighboring islands for a 9‐year period (2004–2012) to gain insight into the best management strategies for these species. The species included two springtime spawners with shorter and longer PLDs, scribbled rabbitfish (Siganus spinus; 33 days) and yellowfin goatfish (Mulloidichthys flavolineatus; ~90 days maximum), and a fall spawner with a similarly long PLD, bluespine unicornfish (Naso unicornis; ~94 days maximum). An ocean circulation model coupled with a particle dispersal model provided simulated numbers of larvae settling at each island in relation to the island where they were spawned. Graph analysis was used to examine generational connections between islands. For S. spinus, self‐seeding was the dominant means of replenishment at Guam. Local management actions to maintain adequate spawning stock may be a primary control on long‐term sustainability for that fishery. In contrast, N. unicornis and M. flavolineatus populations at Guam were reliant on outside sources for 92%–98% of larval supply. For them, identifying and negotiating the preservation of upstream spawning potential in the Marshall Islands and Federated States of Micronesia will be needed. Guam played a relatively minor role in generational connectivity across the region. Shortest paths spanning the region often did not pass through Guam, or there were equally short paths through other islands.  相似文献   

14.
This study was performed to determine the effect of starvation and delayed feeding on activities of digestive enzymes and alkaline phosphatase (ALP) of larval red swamp crayfish (Procambarus clarkii), so as to reveal the tolerance to prolonged starvation and the recovery of digestive enzymes after delayed feeding in larval and juvenile P. clarkii. In the control group, activities of trypsin and ALP increased significantly (p < .05) with day‐age and then kept constant at 24 days after hatching (DAH) and 10 DAH, respectively, whereas the activities of amylase and pepsin increased firstly then decreased with day‐age, and the activity of lipase increased firstly then decreased and then increased again during the development period of juvenile P. clarkii (1–31 DAH). In the group with continuous starvation (CS), activities of pepsin and lipase both decreased (p < .05) after fasting, and the activities of pepsin, lipase and trypsin in the groups with delayed feeding all increased (p < .05) and recover to the levels of the control group after food supply. However, the activity of amylase increased (p < .05) in the CS group, and it decreased to normal level after food supply. The ALP activity did not significantly (p > .05) vary after starvation, whereas it decreased in the groups with delayed feeding after 1 day of food supply, and then increased back to the level similar with the control group. Results from this study could provide information for diet preparation and feeding regime in larval and juvenile red swamp crayfish culture.  相似文献   

15.
Determining the factors that influence recruitment to sequential ontogenetic stages is critical for understanding recruitment dynamics of fish and for effective management of sportfish, particularly in dynamic and unpredictable environments. We sampled walleye (Sander vitreus) and white bass (Morone chrysops) at 3 ontogenetic stages (age 0 during spring: ‘age‐0 larval’; age 0 during autumn: ‘age‐0 juvenile’; and age 1 during autumn: ‘age‐1 juvenile’) from 3 reservoirs. We developed multiple linear regression models to describe factors influencing age‐0 larval, age‐0 juvenile and age‐1 juvenile walleye and white bass abundance indices. Our models explained 40–80% (68 ± 9%; mean ± SE) and 71%–97% (81 ± 6%) of the variability in catch for walleye and white bass respectively. For walleye, gizzard shad were present in the candidate model sets for all three ontogenetic stages we assessed. For white bass, there was no unifying variable in all three stage‐specific candidate model sets, although walleye abundance was present in two of the three white bass candidate model sets. We were able to determine several factors affecting walleye and white bass year‐class strength at multiple ontogenetic stages; comprehensive analyses of factors influencing recruitment to multiple early ontogenetic stages are seemingly rare in the literature. Our models demonstrate the interdependency among early ontogenetic stages and the complexities involved with sportfish recruitment.  相似文献   

16.
The tropical gar (Atractosteus tropicus) is an economically and socially important freshwater fish species from southeastern Mexico, with high aquaculture potential. This study determined the expression of acetyl‐CoA carboxylase (ACC1), fatty acid synthase (FAS), and carnitine palmitoyl transferase 1 (CPT1C) in several tissues of adult specimens, as well as in early ontogeny stages of tropical gar. Partial sequences of all genes were obtained for brain, liver, muscle, mesenteric adipose, kidney, testis, gill, and heart in males. Specific qPCR primers were used to compare the expression between tissues and also during larviculture, starting with embryos (0 days after hatching, [DAH]), and at 5, 10, 15, 20, 25, and 30 DAH. Mesenteric adipose tissue, liver, and muscle showed maximum FAS, ACC1, and CPT1C expression. Additionally, the highest expression of lipogenic genes was detected in embryos (0 DAH), decreasing between 5 and 10 DAH, then increasing at 15 DAH, and ultimately decreasing again from 20 DAH onwards. Based on these results, it can be concluded that genes encoding ACC1, FAS, and CPT1C are expressed differentially across tissues of tropical gar adults, and are regulated during larval development.  相似文献   

17.
Diadromous fishes are known biotransport vectors that can move nutrients, energy and contaminants in an upstream direction in lotic ecosystems. This function has been demonstrated repeatedly in anadromous salmonids, but the role of other diadromous species, especially tropical taxa, as biotransport vectors is less studied. Amphidromous fish species exhibit potential to act as upstream vectors of nutrients and contaminants in their postlarval and juvenile stages, but this role is largely unknown because of limited understanding of larval growth habitats. Moreover, because some species are harvested in artisanal fisheries as postlarvae, and postlarvae are consumed by riverine and estuarine predators, heavy contaminant loads may present a human or wildlife health concern. This research incorporates stable isotope and contaminant analyses to infer larval habitats and contaminant accumulation of amphidromous fishes on the Caribbean island of Puerto Rico. The isotopic signatures of postlarval amphidromous fishes indicated marine basal sources and food web components, rather than those from riverine habitats. Additionally, postlarvae did not contain concentrations of anthropogenic pollutants that would be of ecological or human health concern. These findings are the first and strongest evidence that amphidromous fish postlarvae function as biotransport vectors of marine nutrients into and up river ecosystems without posing a health threat to the receiving food web or human consumers.  相似文献   

18.
Many organisms exhibit compensatory growth (CG), an accelerated growth rate during recovery from periods of low nutrient resources. Despite numerous studies, many aspects of CG, particularly fine‐scale temporal effects early in life, remain poorly understood. We manipulated early‐life feeding regimens in threespine stickleback (Gasterosteus aculeatus) to study compensatory responses in growth rate and lipid storage during the first growing season. Laboratory‐reared stickleback, including ancestral oceanic and derived freshwater populations, were divided into three age‐specific dietary treatment groups – DPR1, DPR2 and DPR3 – which were exposed to a half‐ration nutrient deprivation for 30 days at the onset of 2, 3 and 4 months of age, respectively. We hypothesised that these month‐long periods of nutrient deprivation would result in strong, yet variable CG responses across stickleback populations and dietary treatments following a return to optimal ration levels. The youngest two age classes of fish (DPR1 &and DPR2) exhibited strong CG responses, matching growth rates and lipid generation levels seen in control fish fed an ad libitum diet. The oldest nutrient‐deprived group (DPR3) showed a reduced CG response, with body growth recovering only partially, and lipid levels exhibiting even less recovery. Our results demonstrate that compensatory growth responses in juvenile stickleback depend on the timing of deprivation during the first growing season and further that responses to late‐season deprivation have favoured development of a larger body frame entering the overwintering season over lipid regeneration.  相似文献   

19.
To explore which lifestages affect the stock size of young-of-the-year mantis shrimp Oratosquilla oratoria in Tokyo Bay, Japan, we investigated interannual variations in the quantitative relationships among egg production, larval density, and juvenile density. We collected adult females, larvae, and juveniles during monthly field surveys from 2004 to 2007. The interannual trend for the juvenile density index differed from those for egg production and larval density; although indices of both egg production and larval density were high in 2004 and 2007, the juvenile density index was high only in 2007, suggesting high mortality during the pelagic larval stage or the early phase of the postsettlement juvenile stage in 2004. We found that larval settlement started at the end of August and peaked in October, although larvae from the early spawning season (May–June) should have settled in August or earlier. Juveniles were found throughout the bay except in areas where bottom hypoxia occurred, suggesting that hypoxia restricts the spatial distribution of juveniles. Our results suggest that mortality during the early life history fluctuates among years, probably because of changes in environmental conditions in the bay, resulting in interannual variation in the stock size of young-of-the-year juvenile O. oratoria.  相似文献   

20.
Holothuria tubulosa (Gmelin, 1788) has recently shown an increased demand in Asian markets, becoming one of the intensively exploited holothurian species in the Mediterranean Sea. A risk is that over‐harvesting is likely affecting both the species' natural stocks and the benthic communities. In this scenario, sea ranching and restocking through aquaculture could assist in mitigating its overexploitation. This study is the first to demonstrate the successful artificial breeding and rearing of H. tubulosa, and its consequent potential as a new species for the Mediterranean aquaculture industry. Here we describe the spawning induction, larval development and early juvenile growth in hatchery cultures, aimed at developing a spawning and rearing protocol for this species. The trials were conducted from July to October in both 2014 and 2015. Holothuria tubulosa was induced to spawn by testing four different methods. Thermal stimulation plus thermal shock emerged as the most efficient method to obtain active and healthy gametes. Larval development in H. tubulosa progressed through five stages, reaching the juvenile stage in 27 days. Two different microalgal feeding regimens were tested for larval breeding. Under the best feeding conditions, 7% of the larvae metamorphosed into settled juveniles, adhering to artificial substrates previously conditioned with benthic biofilm. Our results indicate that H. tubulosa shows good performance in hatchery rearing during the larval phases, indicating that this species could be a new candidate for aquaculture in the Mediterranean region, both for production and restocking proposes.  相似文献   

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