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1.
Growth rate in a population of the freshwater crayfish,Paranephrops planifrons white 总被引：1，自引：1，他引：0
C. L. Hopkins 《新西兰海洋与淡水研究杂志》2013,47(4):464-474
Observations on growth increments at moult in a population of freshwater crayfish, Paranephrops planifrons, were made from periodic recaptures of marked animals. The growth increment increased with increasing size of crayfish up to about 20 mm carapace length (65 mm total length) after which a slight decrease was evident. By analysis of the size distributions in samples taken at different times of year it was found that four to five year classes were normally present. Growth of these age components could be followed through consecutive samples. Mean size at leaving the parent in December was 3.5 mm, after one year 11.4–11.8 mm, after two years 18.2–19.3 mm, after three years 22.1–23.8 mm, and after four years 26.7–29.6 mm, all sizes quoted as carapace lengths. After sexual maturity growth in the females was less than in the males. The number of moults completed by each year class was found by relating data on growth increment per moult to growth shown in consecutive quantitative samples. In the first year of life nine moults were completed, in the second year three moults, in the third year two moults, and in the fourth one moult. Independent data on moult frequency recorded from marked crayfish agreed well with these figures. 相似文献
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Based on the non-dimensional general function for the thermal structure features presented by S. A. Kitaigorodsky et al. (1963, 1965)[10,11]. this paper tries to establish semi-empirical and semi-theoretical models bfor the thickness of the upper homogeneous layer of the ocean, thermocline intensity and lower oundary depth of thermocline by consecutive observations from 159 stations in the Bohai Sea,Huanghai Sea and East China Sea in the warm half of the years from 1957 to 1964 and the heat budget at the sea surface computed with the simplified computing formulae proposed by Wang (1983)[22]. This model indicates the main factors forming the thermal structure features in the upper layer of the ocean and their function. With the model, one can directly use the sea surface temperature, air temperature and wind speed to compute the thermal feature in the upper layer of the ocean. 相似文献
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The role of vitellogenin in the transport of organochlorines was investigated in Atlantic croaker (Micropogonias undulatus) by exposing them through the diet to o,p′-DDT at a concentration of 10.8 μg/100 g fish/day for 14 days or Aroclor 1254 (PCB) at a concentration of 0.5 mg/100 g fish/day for 30 days during gonadal recrudescence. Tissue samples were taken from the fish at various times after initial exposure, and o,p′-DDT and PCBs were extracted in acetonitrile and analyzed by gas chromatography. Analysis of the ovarian tissue collected 2 and 3 weeks from the start of exposure revealed that the o,p′-DDT concentration increases as the gonadosomatic index (GSI) increases (r2 = 0.63), with accumulation ranging from less than 1% to as much as 8% of the total dosage. Interestingly, o,p′-DDT did not accumulate in the testes during the same exposure period. Accumulation of PCBs was found to be 40 times higher in the ovaries than in the testes. Gel filtration of plasma from exposed females showed that o,p′-DDT elutes in the low density lipoprotein and vitellogenin fractions. Control plasma incubated with o,p′-DDT at 4 °C for 16 h followed by chromatography on Sepharose 6B gave similar results with an o,p′-DDT concentration of 0.6μg/mg protein in the vitellogenin fraction. Furthermore, both o,p′-DDT and PCBs were found to bind to purified croaker vitellogenin. These results suggest that lipoproteins, including vitellogenin, are involved in the transport and accumulation of organochlorines in the ovaries of exposed fish. 相似文献
4.
Environmental influences on temporal patterns of settlement in two littoral labrid fishes in the Mediterranean Sea 总被引：1，自引：1，他引：1
Correlations between daily fish settlement and environmental and physical parameters were examined during two consecutive years in two labrid species (Symphodus roissali and Symphodus ocellatus) in the NW Mediterranean Sea. Both these species have a short planktonic larval duration (12±0.3 and 9±0.4 days, respectively) and limited offshore larval dispersal. Time-series analysis was used to compare the daily settlement patterns with various environmental variables, and non-linear generalized additive models (GAM) were used to examine the relationship between environmental conditions averaged over larval period and daily settlement patterns. Settlement was not uniform and took place as pulses of different length. Although the analyses detected a few significant correlations between day-to-day patterns in environmental variables and settlement (e.g. solar radiation, atmospheric pressure, daytime or nocturnal wind components), these were not consistent among years. In S. ocellatus, however, wind components (daytime or nighttime) explained part of the variance in settlement intensity. The correlations (GAM outputs) observed between settlement patterns and environmental variables (averaged during the whole planktonic period) suggest that calm weather during the planktonic period usually increases settlement success. 相似文献
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Climate variability and planktonic communities: The effect of an extreme event (severe drought) in a southern European estuary 总被引：1，自引：2，他引：1
Snia Cotrim Marques Ulisses Miranda Azeiteiro Filipe Martinho Miguel ngelo Pardal 《Estuarine, Coastal and Shelf Science》2007,73(3-4):725-734
As a consequence of climate change, flood and drought events are increasing in frequency throughout the world. Nevertheless, knowledge of the effects on zooplankton estuarine communities is still scarce. The present study aimed to examine zooplankton ecology over two contrasting environmental conditions: regular years and extreme dry years, in a shallow temperate southern European estuary, the Mondego Estuary (Portugal). Monthly samples were carried out during three consecutive years: 2003 characterized as a regular temperate year concerning precipitation and river flow, and an extremely dry period during 2004–2005. The spatial and temporal structure of the biological data was evaluated by a three-mode principal component analysis (PCA), which allowed us to distinguish three distinct ecological areas based on their biological composition and their relationship with hydrologic parameters. The severe drought in 2004–2005 was responsible for spatial shifts in the estuary regarding zooplankton community and interannual variability, with an increase in abundance and diversity during the period of low freshwater flow. This freshwater flow regime influenced the composition of the zooplankton community at the most upstream section of Mondego estuary (zone 3), with a replacement of the freshwater community by one predominantly dominated by estuarine organisms. The occurrence of such estuarine community contributed to the increase in zooplankton abundance which is ascribed to the estuarine species Acartia tonsa. The comparison with previous data obtained for this estuarine ecosystem, demonstrated the occurrence of a different scenario at times of high freshwater flow, being defined the existence of two sub-estuarine systems, the north and south arm, presenting the south one the highest values of abundance. 相似文献
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在对东海的自由生活海洋线虫进行分类和多样性研究中,发现2个我国新纪录种并进行了描述。深海螺旋球咽线虫Spirobolbolaimus bathyalis Soetaert&Vincx,1988的主要鉴别特征为:体表具显著的环纹,头感觉器呈乳突状,化感器螺旋形,口腔中部具有一个背齿以及一对亚腹齿,咽前后各有一个咽球;具有两条弧形的交接刺,引带呈板状,无肛前辅器,具两个反向排列的直伸精巢。伸长丝瘤线虫Filoncholaimus prolatus Hopper,1967的主要鉴别特征为:体表光滑,内唇感觉器乳突状,十根头刚毛,口腔具一背齿及两个等大的亚腹齿,尾锥状,渐变为长丝状,锥状部分具尾刚毛;交接刺呈弧形,引带简单,板状,无引带突,具两个乳突状的肛前辅器和两个反向排列的直伸精巢。 相似文献
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Valerio Visconti Elizabeth D. L. Trip Marc H. Griffiths Kendall D. Clements 《新西兰海洋与淡水研究杂志》2018,52(1):82-99
The leatherjacket Meuschenia scaber is widely distributed in Australasian waters, and is a valued bycatch of inshore bottom trawl fisheries although little is known of its life history. Here, we describe the reproductive biology of the species based on 651 leatherjackets sampled in the Hauraki Gulf, New Zealand, between July 2014 and March 2016. The maximum total length (LT) recorded for females and males were 320 and 315?mm, respectively, with both sexes present in all size classes. Monthly analysis of gonad condition revealed a clear spawning season from late austral winter to early summer (August–December), and histological analysis of the ovaries revealed that M. scaber is an indeterminate serial spawning gonochorist. The estimated sizes at sexual maturity (L50) for females (189.9?mm LT) and males (188.4?mm LT) did not differ significantly. Relatively small testes, sexual dimorphism and underwater observation of nesting suggest that M. scaber is a paired spawner. 相似文献
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Metazoan parasites in intertidal cockles Cerastoderma edule from the northern Wadden Sea 总被引：2，自引：0，他引：2
At four intertidal sites near the island of Sylt (eastern North Sea), 13 metazoan parasite taxa were found in 1400 cockles investigated, with digenean trematodes being dominant. Almost all cockles were infected by parasites and most individuals harboured more than one parasite species. We observed four conspicuous patterns: (1) Adult cockles harboured a two times higher species richness (2003: 6.1 ± 0.7 species/host; 2004: 7.1 ± 0.7) than juveniles (2003: 2.9 ± 0.8; 2004: 3.4 ± 0.8) and total parasite community composition significantly differed between age groups. (2) Infection levels were 2–52 times higher in adult cockles than in juveniles both in trematode species and in non-trematode species. In the dominant trematodes, species utilising cockles as first intermediate host (Gymnophallus choledochus, Labratrema minimus, Monorchis parvus) only occurred in adult cockles, and prevalences were low (2–12%). Prevalences of up to 100% were reached by trematodes using cockles as second intermediate host (Himasthla elongata, H. continua, H. interrupta, Renicola roscovita, Psilostomum brevicolle, Meiogymnophallus minutus, Gymnophallus gibberosus). Metacercariae of these species were segregated between body parts within cockles. (3) High spatial heterogeneity in parasite community composition and infection levels occurred between sampling sites. However, communities in juveniles were more similar than communities in adults. (4) Temporal variation in parasite community composition was low between two consecutive years, especially for adult cockles. The omnipresence of parasites in this dominant bivalve species has important implications for sampling designs and as a potentially confounding variable in e.g. physiological studies. It suggests strong and cumulative negative effects on the cockle hosts. 相似文献
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黄海浒苔绿潮防灾减灾现状与早期防控展望 总被引：4，自引：2，他引：2
截至2019年，浒苔绿潮连续12年大规模暴发，对近海生态系统、沿岸环境与社会经济造成严重影响，已经成为黄海最严重的生态环境问题。本文总结了黄海浒苔绿潮防灾减灾现状与成效，分析了存在的问题，然后基于对该绿潮起源与成因的认识，将其早期分为3个关键过程，即浒苔微观繁殖体在养殖设施上的着生与生长过程，定生浒苔脱离附着基形成漂浮浒苔过程，浅滩漂浮浒苔进入深水区形成大面积绿潮过程。最后分别从加强新材料与技术研发防控绿藻着生、强化养殖设施回收管理严控定生绿藻落滩、浅滩汇聚通道拦截打捞等3种途径提出了早期防控措施建议，以期为黄海浒苔绿潮的源头防控提供科学依据。 相似文献
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The South African coastline has been invaded by numerous alien species. Rare pre-invasion (1980) and post-invasion datasets (2001 and 2012) exist for Marcus Island, a small land-tied island in Saldanha Bay, South Africa. These snapshot datasets of the island’s intertidal invertebrate community were complemented with monitoring across seasons, from 2014 to 2016. Invertebrate communities were compared among the summers of 1980, 2001, 2012, 2014, 2015 and 2016 to assess interannual differences, while invertebrates and algae were monitored quarter-annually to assess seasonal changes. In addition, the population dynamics of the alien mussel Mytilus galloprovincialis were monitored. Differences in invertebrate communities between consecutive summers were significant but much smaller than changes induced by the arrival of alien species. Invertebrate and seaweed communities differed among years and shore zones but not among seasons, whereas species diversity differed among years, seasons and shore zones, with zones having the strongest influence. The invasion by M. galloprovincialis, and ensuing spatial and temporal variability in its recruitment, emerged as the most important factor influencing community composition, overshadowing interannual and seasonal changes. This work highlights that the impacts of alien species can be distinguished from natural variability by combining long-term monitoring with surveys at finer temporal scales. This is an important step in extending our understanding of the impacts of marine alien species. 相似文献
12.
Changes in life cycle of the Ponto‐Caspian amphipod Pontogammarus robustoides at in the northernmost part of its range 
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下载免费PDF全文 Nadezhda A. Berezina 《Marine Ecology》2016,37(6):1434-1446
The aim of this study was to investigate the dynamics of abundance, population structure and reproductive variables of the invasive Ponto‐Caspian amphipod Pontogammarus robustoides in its northernmost population, located in the Baltic Sea. Pontogammarus robustoides population variables were studied every month from May to October over 7 years (2002–2008) at two locations in the eastern part of the Gulf of Finland, one site in the north and one in the south. Observations of macrozoobenthos were also conducted once per year in July at 12 sites in this gulf during 2002–2014. This was to monitor the distribution area of P. robustoides and its abundance/biomass in different parts of the Gulf. The results showed that P. robustoides is a widely spread species in the Gulf, preferring to colonize stone‐sandy, vegetated and littoral habitats, from the shore to a depth of 5 m, with water salinity of 0.2–3 ppt. This species co‐exists with other amphipods, such as the Baikalian Gmelinoides fasciatus, the North Atlantic Gammarus tigrinus and the native Gammarus spp. The abundance of P. robustoides varied between the two study sites and among years (2002–2008), reaching a maximum level of 1000 ind.·m?2 for adults and 3000 ind.·m?2 for juveniles. The temperature‐dependent duration of egg development (embryogenesis) in the amphipod and the annual number of generations in P. robustoides populations varied among years. Three generations were recorded in most years and two generations in the coldest years. Clutch size (or fecundity) was dependent on the body length of female and averaged between 33 and 43 eggs per clutch for females ranging in body length from 11.2 to 12.2 mm. A maximum of 75 eggs were observed in a female with a body length of 16 mm. This paper concludes that life‐cycle variables change when P. robustoides spreads from the southern (Ponto‐Caspian region) to northern (Baltic Sea) range areas. In the studied northernmost location, the fecundity and number of generations of this amphipod were 1.5–2‐fold lower compared with the more southern locations. In addition, these variables and P. robustoides abundance were different between the coldest and warmest years at study sites that testify about their distinct dependence on local environmental conditions; further changes in life cycle of this species may be expected together with current climate warming. 相似文献
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The narrow-barred Spanish mackerel Scomberomorus commerson is one of the most important linefish species caught in KwaZulu-Natal and southern Mozambique waters, forming the basis of important commercial, artisanal and recreational fisheries. A total of 439 S. commerson were sampled along the east coast of southern Africa (KwaZulu-Natal, South Africa, and southern Mozambique) between April 2011 and March 2012. Retrospective length-at-age data observed from whole otoliths were used to compare and describe sex-specific growth. Growth rates obtained from otolith-derived data were compared with those estimated from 29 tag-recaptured fish. Overall, ages ranged from 0.48 to 14.6 years for females and 0.4 to 13.57 years for males. Otolith readings yielded an average percent error of 11.21%, lower than recorded in a previous study from the region. Marginal zone analysis provided strong evidence that one translucent and one opaque growth zone were laid down annually. Schnute growth-function parameters indicated significant differences in growth between sexes. Females approached their mean asymptotic length at a faster rate, and grew to a greater mean length-at-age, relative to males. Growth in both sexes was rapid, achieving 67.46 cm FL (females) and 65.4 cm FL (males) in their first year of life. Growth rates obtained from tag-recaptured S. commerson indicated slower growth for smaller/younger fish up until 70 cm FL after which growth was very similar to that observed from otolith-derived data. The results of this study provide accurate, validated life-history parameters for king mackerel that are important for the assessment of stock status in the region. 相似文献
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An opportunistic macrobenthic assemblage was studied from 2001 to 2003 in a central area of the Cabras lagoon (western Sardinia, Italy), known to be affected by environmental disturbances (i.e. organic over-enrichment of sediments, and episodic events of hypoxia/anoxia and sulphide development). We identified recurrent seasonal changes in this macrobenthic assemblage, with a general impoverishment in summer and a recovery in winter/spring. The nereids Neanthes succinea and Hediste diversicolor were found to replace the spionid Polydora ciliata as the most dominant species in the summer for 3 consecutive years. Occasional, unsynchronized appearances of small-sized deposit feeders, such as Tubificidae, Capitella cf. capitata, chironomid larvae and Hydrobia spp., were observed in winter/spring. We suggest that these changes are driven by the interplay of environmental conditions (worse in summer) with numerous biotic factors. This includes different tolerance levels of taxa to low oxygen concentrations and sulphides, variability in larval supply and post-larval transport, as well as competition for space and food between and within different functional groups, and facilitation through animal bioturbation and sediment reoxidation. A conceptual model is proposed to demonstrate how environmental conditions and biotic interactions may control the benthic assemblage in such a harsh lagoon environment. 相似文献
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《African Journal of Marine Science》2013,35(1):881-889
Pup mortality in the South African (Cape) fur seal Arctocephalus pusillus pusillus was measured throughout the pupping seasons over consecutive years (1987–1991) at two large mainland colonies in Namibia. Cumulative rates of mortality were obtained by counting live and dead pups every second day. Most young pups die shortly after birth in November/December each year, following which there is a decline in the rate of mortality. The average rate of mortality from birth to age 30 days at the Atlas Bay colony was 20 per cent. There was little inter-colony variation in the mortality rates of pups over the four years of the study. Differential rates of mortality between the sexes were found, significantly more female pups dying. Environmental factors are influential in the deaths of newborn pups at these mainland colonies, a combination of changes in wind velocity and direction leading to heat stress in pups being the most important. 相似文献
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Guiomar Rotllant Carles G. Simeó Guillermo Guerao Marta Sastre Daniel F. R. Cleary Ricardo Calado Alicia Estévez 《Marine Ecology》2014,35(3):298-307
The spider crab Maja brachydactyla is an important commercial species in Europe and supports intensive fisheries in the NE Atlantic. A field survey was performed to assess long‐term and consecutive interannual (2005–2010) variation of the biochemical composition of newly hatched larvae of M. brachydactyla. Larval biochemical profiles differed significantly among years, with pronounced differences being recorded in 2010. Differences among batches of newly hatched larvae were mainly explained by the contribution of triacylglycerols and, to a lesser degree, by protein and lipid content. The use of different nutrition indices is discussed. The biochemical composition of newly hatched larvae from M. brachydactyla was highly variable, even though surveyed broodstock was obtained from the same local population and was always sampled during the same season. The unpredictable biochemical profiles of newly hatched larvae may condition their survival and recruitment. This largely overlooked aspect of larval variability should be considered in future fisheries management strategies and captive production of marine organisms that still rely on wild seeds. 相似文献
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能产生名贵珍珠的合浦珠母贝Pinctada martensi(Dunker)是一种栖息在近岸内湾的暖水性双壳类,是国内外珍珠养殖的主要母贝。 珍珠养殖包括母贝养成和植核育珠两大部分。从母贝育种至养成可供植核的大贝,不论从珍珠养殖的生物学考虑还是从企业的经济效 相似文献
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本研究采用石蜡组织切片和H.E.染色法对军曹鱼原始性腺的形成、分化及精巢和卵巢首周年发育的组织结构变化进行观察。结果显示,军曹鱼原始生殖细胞在7孵化日龄(days post hatching,dph)时迁移到达生殖嵴,随后体细胞出现聚集和分裂,并于15 dph将原始生殖细胞完全包绕形成原始性腺。军曹鱼卵巢分化的时间要早于精巢,34 dph的稚鱼性腺组织尚未分化,但可观察到两种存在明显组织学差异的性腺类型,其中一种类型的性腺出现卵原细胞群,而另一种类型的性腺横切面较狭长,生殖细胞数量明显较少,因此推定为未分化精巢;卵巢的解剖学分化开始于44 dph,其标志为卵巢腔的形成;50 dph时精巢开始细胞学上的分化,此时精原细胞由基底膜包被形成囊泡状的细胞团。在首周年发育期间 (60～360 dph),军曹鱼的精巢发育包含I、II、III、IV、V 5个时期,而卵巢发育只包含I、II、III 3个时期。60 dph时,精巢和卵巢均处于I期;90 dph时,精巢发育至II期,卵巢仍处于I期;120 dph时,超过半数的精巢已发育至 III期,仅少部分卵巢发育至II期;150 dph时,精巢已发育至III期,而大部分卵巢发育至II期;185 dph时,精巢仍为III期,卵巢均已发育至II期;210 dph时,大部分精巢发育至IV期,卵巢仍处于II期;360 dph时,精巢已发育至V期,大部分卵巢发育至III期。上述研究结果可丰富军曹鱼的繁殖生物学研究基础,阐明其早期性腺发育规律,还可为其人工繁殖提供理论依据。 相似文献