Temporospatial dynamics and public health significance of bacterial flora identified on a major leatherback turtle (Dermochelys coriacea) nesting beach in the Southern Caribbean

Grande Riviere beach, on the island of Trinidad, supports the largest nesting population of leatherback turtles in the Caribbean region. Throughout the nesting season, nests are naturally disturbed by newly nesting females, resulting in egg breakage and loss of some nest viability. This environment is ideal for the growth and proliferation of microorganisms. The range of bacterial flora present in beach sand and egg shells was examined, with emphasis on bacteria that may pose a threat to public and animal health. The extent to which the bacterial load and genera on the beach changed throughout the season was also assessed. Twenty‐five genera were identified, with Pseudomonas spp. found to be the most predominant environmental bacteria. Four genera identified possess zoonotic potential, while five additional genera are known to be of public and animal health significance. Distinct shifts in the density and distribution of bacteria were observed along the beach from early to peak nesting season. Shifts were seen across heavily traversed zones, thus highlighting the potential exposure threats posed to beach visitors and animals alike. Further studies aimed at speciating this population of bacteria, as well as isolating potential fungal pathogens may mitigate this threat. Identification of bacterial agents that are specifically pathogenic to leatherback turtles, turtle eggs, hatchlings and those who may interact with these animals will serve to enhance and guide efforts to better conserve this species and protect the health of all who visit this ecologically significant site.     

Is a small sea turtles rookery doomed to local extinction? Decreasing nesting trends at the Paria Gulf,Venezuela

Small rookeries are rarely evaluated for marine turtles worldwide. Two species of sea turtles (Hawksbill, Eretmochelys imbricata; Leatherback, Dermochelys coriacea) nest on five main beaches of the northeast coast of the Paria Gulf in Venezuela. Population trends using generalized linear models at this rookery were assessed and compared with other small rookeries. Both species showed significant negative nesting trends: Nesting by critically endangered hawksbills decreased over nine seasons 2009–2017 (64–142 nests per year, General Linear Model Slope Value = ?0.061; data pooled for five beaches); similarly, vulnerable leatherback nests decreased across the same period in the main beach Los Garzos (0–69 nests/year; GLMSV = ?0.34). Besides human and natural predation of the nests, no significant environmental impacts affect the beaches except probably on Obispo Isthmus where a gas pipeline installation interrupted the nesting activity in 2014. Observed changes to the nesting trends in these small rookeries have a collective impact on broader conservation concerns for sea turtles in the region.     

Monitoring hawksbill turtle nesting sites in some protected areas from the Persian Gulf

Iranian nesting populations of the critically endangered hawksbill turtle(Eretmochelys imbricate) are some of the most important in the Indian Ocean. In this study, four of the most important hawksbill nesting grounds in the Persian Gulf, situated within three Iranian marine protected areas, were surveyed during nesting season,including Nakhiloo, Ommolgorm and Kharko Islands and the mainland beaches of the Naiband Marine-Coastal National Park(NMCNP). We present GIS maps of these key nesting grounds and describe sand texture of key nesting zones, along with conservation recommendations. About 9.2(28.3%) out of 32.5 km of all shores surveyed in this study were used by nesting hawksbill turtles follows: Nakhiloo: 1.4 km(52% of potential nesting area);Ommolgorm: 1.94 km(40%); Kharko: 3.4 km(28%), and NMCNP: 2.46 km(18.9%). The average nesting density was calculated as 131 nests/km at Nakhiloo, 76 nests/km at Ommolgorm, 7 nests/km at Kharko, and 15 nests per km at NMCNP. Highest nesting density was observed in Nakhiloo and Ommolgorm. It is thought that high hawksbill nesting density in these islands seems likely a result of limiting adequate nesting shores rather than the size of population, and also low density in Kharko and NMCNP more related to past and current pressures and low population density. With the exception of Ommolgorm Island, sands at the nesting grounds were well sorted.Grain size indicated that female hawksbill turtles in the Iranian Persian Gulf nest in sands that are generally mixed, with mean grain size ranging from coarse sands(0.4Φ;～0.5–1 mm) to fine sands(2Φ;～0.25 mm). We provide and discuss conservation recommendations and suggestions for future.     

Nesting ecology and hatching success of the hawksbill turtle (2004–2014) on Cousine Island,Seychelles

Populations of the Critically Endangered hawksbill turtle Eretmochelys imbricata in the Seychelles showed significant declines in the past. They have since recovered and nesting numbers are increasing because of increased protection and management intervention. Data on their nesting ecology on Cousine Island were collected and analysed for the breeding seasons from 2004/2005 to 2013/2014 with the aim of improving management methods. The findings indicate that the number of nesting individuals increased during the study period (from x? = 34.3 nesters between 2004 and 2009, to x? = 55.4 nesters between 2010 and 2014); however, the clutch frequency was relatively low compared with other study areas. Night-time nesting increased, most likely because of increased disturbances across the study period. Clutch sizes decreased significantly across the nesting season, and there was a significant drop in hatching success in clutch sizes exceeding 200 eggs. The predation rate and infertility rate each showed an increasing trend over time. Nests incubating in full sun showed the highest mean hatching success rate and had the shortest mean incubation duration. The present study provides insight into the species’ nesting ecology on Cousine Island and will better inform management decisions aimed at increasing hatching success and minimising threats such as beach erosion and predation.     

Relationship of Caspian tern foraging ecology to nesting success in the Columbia River estuary, Oregon, USA

The prevalence of juvenile salmonids (Oncorhynchus spp.) and marine forage fishes in the diet of Caspian terns (Hydroprogne caspia) nesting in the Columbia River estuary has been established, but the relationship between diet composition, foraging distribution, and productivity of these birds has received little attention. We used radio-telemetry and on-colony observations to relate changes in off-colony distribution to patterns of colony attendance, diet composition, and productivity of adult terns nesting on East Sand Island during two years of different river and prey conditions. Average distance from the East Sand Island colony (located in the marine zone of the estuary) was 38% (6.6 km) greater in 2000 compared to 2001, associated with lower availability of marine forage fish near East Sand Island and lower prevalence of marine prey in tern diets. Colony attendance was much lower (37.0% vs. 62.5% of daylight hours), average trip duration was 40% longer (38.9 min), and nesting success was much lower (0.57 young fledged pair⁻¹ vs. 1.40 young fledged pair⁻¹) in 2000 compared to 2001. Higher proportions of juvenile salmonids in the diet were associated with relatively high use of the freshwater zone of the estuary by radio-tagged terns, which occurred prior to chick-rearing and when out-migrating salmonid smolts were relatively abundant. Lower availability of marine prey in 2000 apparently limited Caspian tern nesting success by markedly reducing colony attendance and lengthening foraging trips by nesting terns, thereby increasing chick mortality rates from predation, exposure, and starvation.     

Nest Densities of the Wandering Albatross Diomedea Exulans at the Prince Edward Islands,Estimated Using Gps

Hand-held Global Positioning System (GPS) receivers provide opportunities for detailed and rapid mapping of features, including biological ones, further enhanced by the removal during 2000 of "selective availability". GPS was used to map, describe and compare nest densities within wandering albatross Diomedea exulans colonies at subantarctic Marion and Prince Edward islands. On Prince Edward Island, the coordinates of 1 061 wandering albatross nests were determined and, on Marion Island, 1 779 nests. For describing nest densities of wandering albatrosses, a 50-m grid is recommended, at which scale, the densest area of Prince Edward Island was in Albatross Valley, where the area of the colony was 46 ha and nest density was 22.3 nests ha^?1. For Marion Island, the total area of the wandering albatross colonies was 306 ha and the nest density was 5.8 nests ha^?1. In the three study colonies there (Macaroni Bay, 28 nests; Sealer's Beach, 117 nests; Goney Plain, 140 nests), the density statistics did not differ greatly from the overall densities on the island, with overall mean densities of 4.9, 5.7 and 8.0 birds ha^?1 respectively. Although comparisons with nest densities at other breeding colonies are uncertain because of differing methods of computing them, the nest densities in Albatross Valley lie within the reported ranges for other colonies of great albatrosses.     

The impact of open boundary forcing on forecasting the East Australian Current using ensemble data assimilation

We investigate the performance of an eddy resolving regional ocean forecasting system of the East Australian Current (EAC) for both ensemble optimal interpolation (EnOI) and ensemble Kalman filter (EnKF) with a focus on open boundary model nesting solutions. The performance of nesting into a global re-analysis; nesting into the system’s own analysis; and nesting into a free model is quantified in terms of forecast innovation error. Nesting in the global reanalysis is found to yield the best results. This is closely followed by the system that nests inside its own analysis, which seems to represent a viable practical option in the absence of a suitable analysis to nest within. Nesting into a global reanalysis without data assimilation and nesting into an unconstrained model were both found to be unable to constrain the mesoscale circulation at all times. We also find that for a specific interior area of the domain where the EAC separation takes place, there is a mixture of results for all the systems investigated here and that, whilst the application of EnKF generates the best results overall, there are still times when not even this method is able to constrain the circulation in this region with the available observations.     

珠江口典型海岛周边水域浮游植物分布特征及其影响因素*

旅游业为海岛带来可观经济效益的同时, 人类活动也导致水体生态环境恶化, 如水体富营养化加剧、赤潮频发等。文章通过对珠江口东南部典型海岛——庙湾岛和外伶仃岛周边水域丰水期和枯水期现场环境数据与浮游植物分布特征的对比研究, 分析珠江径流等自然因素以及人类活动对河口天然海岛周边水体生态的潜在影响。枯水期外伶仃岛和庙湾岛周边水域海水分别镜检鉴定出76种和74种浮游植物, 两个海岛浮游植物平均细胞密度分别为2.62×10⁴个·L^-1和2.08×10⁴个·L^-1; 丰水期则分别鉴定出38种和47种浮游植物, 平均细胞密度分别为52.91×10⁴个·L^-1和170.57× 10⁴个·L^-1。在外伶仃岛和庙湾岛, 丰水期中肋骨条藻(Skeletonema coatatum)均为绝对优势种, 而枯水期两个岛的最主要优势种分别为窄隙角毛藻(Chaetoceros affinis)和新月筒柱藻(Cylindrotheca closterium), 物种多样性指数均明显高于丰水期。两个海岛微型浮游植物相对于其他两个粒级常占据优势地位, 但在丰水期, 小型浮游植物贡献明显上升, 其中外伶仃岛相对于枯水期由16.32%升至26.75%, 庙湾岛则由12.12%升高至24.78%。两个海岛在丰水期和枯水期均仅检出聚球藻(Synechococcus, Syn)和真核微微型藻类(eukaryotic, Euk)两大微微型浮游植物类群, 两者细胞密度分别为~10⁷个·L^-1及~10⁸个·L^-1量级。与环境因子的对比分析表明, 两个海岛浮游植物的区域分布与季节变化受多种因素影响, 其季节性差异主要受径流影响强度、影响范围以及相应的盐度、营养盐等环境因素的季节变化所调控。丰水期岛屿屏蔽效应对浮游植物丰度的区域分布特征有显著影响, 无论小型浮游植物还是微微型浮游植物均发现存在迎流面出现丰度高值分布的现象, 但对群落结构的分布影响不明显; 在枯水期, 水体环境很可能主要受人类活动与水体垂直混合扰动的综合影响, 总体上浮游植物分布的区域差异较小。     

Breeding success of African penguins Spheniscus demersus at Dassen Island,especially after oiling following the Apollo Sea spill

The reproductive success of African penguins Spheniscus demersus at Dassen Island from 1994 to 2000 was variable, but much higher than previously reported figures for the species. Breeding success was positively related to the abundance of anchovy Engraulis encrasicolus and sardine Sardinops sagax, and the high reproductive output during the study was attributed to the large biomass and high availability of these two species for much of the study period. De-oiled penguins from the Apollo Sea spill had a slightly lower hatching success but a significantly lower overall breeding success than that of un-oiled birds, driven mainly by the reduced number of chicks which fledged. Nests with two de-oiled Apollo Sea parents were less successful than nests with one de-oiled bird. There was increased mortality of chicks 40 days and older in nests with de-oiled birds. Chicks from nests with one de-oiled Apollo Sea parent grew at a similar rate to chicks from nests with no de-oiled parents. However, chicks from nests that comprised two de-oiled Apollo Sea birds had significantly slower growth rates than these other two groups. Breeding success and chick growth at nests with de-oiled birds were more negatively impacted when feeding conditions were less favourable. These results suggest that one of the main reasons for lower breeding success in de-oiled birds was their reduced ability to provision chicks, especially during the period in which the energy demands of the chicks is greatest. The rate of mate fidelity was lower in de-oiled birds than un-oiled birds, and there was a positive association between mate fidelity and breeding success.     

Response of epiphytic foraminiferal communities to natural eutrophication in seagrass habitats off Man O'War Cay, Belize

Eutrophication from a variety of anthropogenic sources is an increasingly prevalent problem in coastal waters, and is one of the factors contributing to the decline of seagrass ecosystems worldwide. This study investigated the impact of natural nutrient enrichment derived from nesting seabird colonies on Man O'War Cay, Belize, on the epiphytic foraminiferal communities living on the seagrass Thalasssia testudinum. Man O'War Cay, a small mangrove island in the central region of the barrier reef complex, hosts nesting colonies of magnificent frigate birds and brown boobies. Epiphytic foraminiferans were surveyed from five stations spaced at 10‐m intervals along a 40‐m transect in a seagrass meadow located off the eastern end of the island (March 2004). Low species diversity and high dominance of the encrusting, dendritic species Cornuspiramia antillarum characterized the epiphytic foraminiferal biota. Species diversity, as measured by the Shannon's H, and evenness, as measured by Buzas–Gibson's E, decreased in an offshore direction. The density of individuals per square centimeter of blade, however, increased in an offshore direction, with the lowest values observed at the station closest to the island, and the highest values recorded at the station farthest from the shore. The results obtained in this study indicate that epiphytic foraminiferal populations respond to nutrient enrichment, and thus may be useful indicators of ecosystem decline in subtropical–tropical, oligotrophic marine habitats.     

Recent population trends of sooty and light-mantled albatrosses breeding on Marion Island

Sub-Antarctic Marion Island is one of the few islands where both species of Phoebetria albatrosses breed sympatrically. The last published assessment of their population trends, which reported counts up to 2008, concluded that the numbers of breeding pairs of sooty albatross P. fusca (Endangered) were decreasing, whereas numbers of light-mantled albatross P. palpebrata (Near Threatened) were increasing. Extending the counts to 2014 reversed these trends, with numbers of sooty albatrosses increasing from 2006 to 2014, and numbers of light-mantled albatrosses decreasing from 2007 to 2014. Confidence in island-wide counts is low due to the cryptic nature of the albatrosses on their largely inaccessible cliff-side nest sites, as well as counts for sooty albatrosses taking place late in the incubation period when 10?20% of nests have already failed. Given the greater conservation concern for the sooty albatross, we recommend that dedicated annual counts be conducted during the early incubation period, and be repeated shortly after the chicks hatch (late December), mid-way through the nestling period (late February) and prior to fledging (late April), to give a better idea of breeding success. Count zones also should be revised to facilitate more accurate counts, ensuring more reliable estimates of sooty albatross population trends at Marion Island.     

Evaluating the impacts of coastal squeeze on sea turtle nesting

Recent studies have provided theoretical and empirical evidence about the importance of hatchling production for sea turtle population dynamics. Therefore, understanding the effect of nesting habitat loss as a factor leading to hatchling reduction is essential in order to establish conservation plans for the recovery of sea turtle populations. In the present study, we developed a method to quantify habitat loss and link it with hatchling production. We used data for loggerhead sea turtles (Caretta caretta) collected at Sekania nesting beach, western Greece, to describe biological and behavioral attributes of nesting individuals. Spatial characteristics of the nesting site were analyzed and alternative scenarios of habitat loss were examined. We then used circle-packing technique to evaluate the impact of an increasingly reduced available nesting area on the spatial distribution of nests. An increased number of nests within the study site resulted in density-dependent processes regulating hatchling production. Under the different scenarios, we evaluated the risk of the laying nests exceeding the estimated carrying capacity of the nesting beach. Our results clearly demonstrated the need to apply direct and efficient conservation measures at Sekania nesting site to minimize further habitat loss from human-related processes and a rising sea level. The approach developed evaluates the effect of habitat loss upon nesting by linking it with quantifiable processes (density dependence), providing a conservation tool to guide planning decisions towards the conservation of the sea turtle population.     

烟台近岸人工鱼礁与自然岩礁底层渔业生物群落特征对比分析

为探究烟台近岸人工鱼礁区的底层渔业群落与自然岩礁区的差异,本研究于2018年5月—2019年2月在位于山东烟台近岸的养马岛自然岩礁区、牟平人工鱼礁区及毗邻泥沙区开展4个季度的渔业调查。调查共发现渔业生物15目37科53种,自然岩礁区与人工鱼礁区的平均物种数的差异不显著,但均明显高于泥沙区(Kruskal-Wallis test, P0.05)。两礁石区的CPUE(catch per unit effort)在各季节均显著高于泥沙区(ANOVA,P0.05),春、夏季自然岩礁的CPUE显著高于人工鱼礁(ANOVA, P0.05)。三个区域的优势种存在一定相似性,但各优势种的CPUE呈现出明显的区域差异,尤其对于许氏平鲉及大泷六线鱼,人工鱼礁的生境优势高于其他两个区域。多样性分析结果显示,自然岩礁区的Shannon-Wiener多样性指数H′最高,其次为人工鱼礁区和泥沙区。自然岩礁与人工鱼礁区Magalef丰富度指数D的差异不显著,但都明显高于泥沙区(ANOVA, P0.05)。ANOSIM分析表明三个海区的群落组成在各季节均存在显著差异(P0.05),主要原因是优势种资源量和分布存在明显的区域差异,这也反映了优势种对群落结构的塑造作用。RDA分析发现,温度、溶氧及水深依次为影响群落结构的主控环境因子,可解释部分群落结构的异质性。本研究证实人工鱼礁可以有效提高以岩礁性鱼类为主的渔业资源量,然而其群落结构复杂度、生物多样性水平与相对成熟的自然岩礁区仍存在一定差距,未来其能否取代或超越自然岩礁的功能,仍需要长时间的积累和观测。     

Factors affecting offspring growth and daily nest survival rates in the coastal breeding Western Reef Heron (Egretta gularis) in the Persian Gulf

Offspring growth and nest survival of waterbirds are important and prominent characteristics of their life history. Nestling growth and daily survival rates of the Western Reef Heron Egretta gularis were studied in Hara Biosphere Reserve, Persian Gulf, Iran. Growth parameters were determined in relation to both age ranking of each nestling within a brood and the brood size using data from known‐age nestlings. Nesting success was modeled based on the information‐theoretic approach implemented by the program MARK to assess the effects of clutch initiation date, nest size and location on daily survival rates of nests. Mean daily growth rate of body mass was 18.06 ± 6.22 g during the first 2 weeks of age and was independent of brood size but was greater in nestlings hatching earlier within the brood. Wing and tarsus growth rate was influenced by both brood size and nestling rank within the brood, but culmen growth was independent of both factors. Earlier hatched nestlings grew faster than those hatched later. Growth of all morphometric parameters followed the Logistic growth curve model except for wing chord, which fitted the Gompertz growth model. Nest size and nest height above the ground were the most important predictors of nest survival (ω_i = 0.79 and ω_i = 0.69, respectively), with survival among Western Reef Heron nests improving as the nest size and nest height increased. This study shows the importance of temporal and spatial variables for breeding ecology of a common but little‐known breeding heron in coastal areas of Persian Gulf.     

Marine artificial micro‐reserves: a possibility for the conservation of endangered species living on artificial substrata

The installation of urban and commercial infrastructures on the coast has a severe impact on the marine environment. This impact is mostly negative but, simultaneously, some of the species that colonize artificial substrata (sometimes rare or threatened) find refuge in man‐made structures. The protection of endangered species is usually provided by marine protected areas or by laws that punish their damage or collection, but effective enclosure and custody must be achieved in the case of easily accessible intertidal species. We used the ferruginous limpet, Patella ferruginea, as a case study because it is the most endangered invertebrate in the Mediterranean. This species, which lives in the intertidal zone and is very accessible to people, is a free‐spawning, protandric hermaphrodite, highly dependent on population density and individual size for its reproductive success. Previous work by the authors found the species is especially abundant on artificial substrates on both shores of the Strait of Gibraltar, where people collect fewer of them. Spanish laws of coastal management do not allow the enclosure of the natural coastline, but artificial installations like harbour breakwaters may be closed or guarded, and visits for educational purposes may be carried out under control. The possibility of declaring some kind of environmental protection for these artificial areas would be a very helpful tool for conservation and management purposes. Protected individuals would grow larger and eventually produce exponentially more offspring, which could be transported by currents to adjacent habitats. Here we propose a protection concept for artificial sites termed Artificial Marine Micro‐Reserve (AMMR), where some endangered species experience a refuge from human disturbance. This concept is a modification of the land micro‐reserves that have been recently declared in small natural sites that keep rare plant species. A network of AMMRs would be the final objective, allowing the creation of a great metapopulation of P. ferruginea and also giving refuge to other endangered species that have been found to grow in this type of substratum. Critically, the declaration of a micro‐reserve cannot be used as a reason in favour of new construction because of the negative influence of such structures on the marine environment, together with the fact that there is no certainty that valuable species will settle on them.     

Differences in trophodynamics of commercially important fish between artificial waterways and natural coastal wetlands

Extensive artificial waterways have replaced natural wetlands and created new estuarine habitats on the southern Queensland coast, Australia. Economically important fish species found in adjacent natural wetlands of mangrove, saltmarsh and seagrass also occur in the artificial waterways. Stable isotope analyses (δ¹³C, δ¹⁵N) were used to test whether the relative importance of basal sources of energy varied for foodwebs found in artificial (canals and tidal lakes) and natural waterways. None of the fish species differed in their isotope values between artificial waterways. In contrast, isotopic signatures of snub-nosed garfish (Arrhamphus sclerolepis; Hemiramphidae) varied greatly between natural and artificial waterways, having highly enriched δ¹³C values (−10.5‰) in natural wetlands, demonstrating reliance on seagrass (−11.4‰), and significantly less enriched values (−19.0‰) in artificial waterways, consistent with either local algal sources (−19.8 to −20.4‰) or a mixture of seagrass and other less enriched autotrophs from adjacent natural wetlands. Isotopic signatures of sand whiting (Sillago ciliata; Sillaginidae) were also significantly more enriched in natural (−18.2‰) than artificial (−21.0‰) habitats, but means were not far enough apart to distinguish between different sources of nutrition. δ¹³C values of yellowfin bream (Acanthopagrus australis; Sparidae) did not differ between artificial and natural habitats (about −20‰ in both). δ¹⁵N values of fish varied among habitats only for A. sclerolepis, which in artificial waterways had values enriched by 2‰ over those in natural waterways. This was consistent with a shift from seagrass (relatively depleted δ¹⁵N) as a source in natural habitat to algal sources (relatively enriched δ¹⁵N) in artificial habitats. This study provides some of the first evidence that at least some fish species rely on different autotrophs in artificial waterways than in adjacent natural wetlands.     

Impact of protective shark nets on sea turtles in KwaZulu-Natal,South Africa, 1981–2008

Shark nets were established along the KwaZulu-Natal coast in 1952 to protect bathers against shark encounters. Sea turtle bycatch data for the period 1981–2008 in these shark nets indicated that loggerheads Caretta caretta were caught most frequently at 40.9 y^–1 or 1.11 km-net^–1 y^–1, followed by green turtles Chelonia mydas at 0.32 km-net^–1 y^–1 and leatherbacks Dermochelys coriacea at 0.14 km-net^–1 y^–1. Catch rate of loggerheads increased throughout the study period, and was positively correlated with the increase in the number of nesting females from the recovering population in Maputaland, South Africa (r = 0.52, p < 0.05, n = 28). This increase is ascribed to successful nest conservation. Leatherback bycatch remained stable, following their nesting trends, although they receive similar conservation efforts on nesting beaches as loggerheads. Bycatch of green turtles, although not a nesting species in South Africa, was stable over time. Mortality varied between species (from 53.2% to 70.6%) with loggerheads being the most hardy, followed by leatherbacks and green turtles. Few hawksbills Eretmochelys imbricata and olive ridleys Lepidochelys olivacea were caught in the shark nets. Fewer sea turtles are caught by shark nets than by longlines and because the nesting populations of loggerheads, green turtles and leatherbacks are either stable or increasing in the South-West Indian Ocean, shark net bycatch was considered negligible and sustainable.     

九龙江口鱼类浮游生物的生态

１９８７年３月到１９８８年２月在九龙江口的５个固定站位上，逐月进行鱼卵和仔，稚鱼调查的资料。结合１９８３年至１９８４年的鉴定资料进行分析，结果表明，该海区的鱼类生态结构系由淡水，半咸水，沿岸和海水鱼类等４种生态类型组成。鱼类主要产卵期为３－９月，盛期为５－８月。鱼卵数量以河口上游最多。种数则以河口下游较多。仔，稚鱼相对集中于河口中游，其数量和种数均为最多。在九龙江口放流，增殖或引进鱼类新种成功的机