Patterns of variability in ichthyoplankton occurrence and abundance in Biscayne Bay,Florida

Within-day variability in ichthyoplankton and microzooplankton abundances was examined at a single station in Biscayne Bay using replicate tows of 61-cm bongo nets and Niskin bottles to determine if patchiness occurred on the 10–1000 m scale and on the minutes to hours time scale. Fish eggs and larvae often were patchy but copepod nauplii, the predominant food of larvae, usually were randomly distributed at the scales examined and over the 3.15 m-depth water column. Mean patchiness index values were of similar magnitude for fish eggs and larvae but fish eggs were patchy more often than were larvae. Individual taxa of larvae had extremely high patchiness index values on some dates. Variability in fish egg catches often reflected increasing or decreasing abundance trends during the 2.5h sampling period while fish larvae catches often appeared to be clumped within the repetitive series of tows. There was no tendency for patchiness to be correlated among taxa on collection dates nor was it correlated with abundances or wind speeds. Patchiness indices of bay anchovy Anchoa mitchilli eggs and larvae were not significantly correlated, indicating little concordance in tendency to be aggregated, suggesting that distributions were influenced by biological processes related to spawning of adults and behaviour of larvae, in addition to physical processes. Although ichthyoplankton patchiness often did exist at the 10–1000 m scale, on many days ichthyoplankton was uniformly or randomly distributed. Copepod nauplii were abundant ($\text{x}\text{=90.41}{}^{\mathrm{?1}}$), randomly distributed on most dates, and apparently readily available as fish larvae food in Biscayne Bay.     

长江口春季鱼类浮游生物群落结构与环境因子的关系

随着源源不断的淡水径流入海与营养物质的输入，使长江口及其邻近海域成为生产力最高的水域，也孕育了我国近海重要的舟山渔场、吕泗渔场和长江口渔场。成淡水的交汇形成了长江口水域复杂的水文物理条件，使之成为众多鱼类的产卵场和育幼场(赵保仁等，1992；罗秉征等，1994)。河口鱼类浮游生物群落结构及其季节变化格局，既受制于其生殖种群的资源量，也与水域环境稳定性密切相关(Blaber et al.，1997；Joyeux，1998；Whitfield，1999)，因而受到国内外的广泛关注。有关以成体为基础的河口鱼类群落生态学已有较多的调查研究(杨伟祥等，1992；朱鑫华等，1994a，b)；而鱼类补充群体的研究，亦多集中于鱼卵和仔稚鱼的种类组成和分布等(杨东菜等，1990；沙学绅，1962)。本文利用1999年5月长江口生态环境与资源综合调査资料，主要研究鱼类浮游生物群落结构及其与环境因子的关系，以期深入探讨河口区鱼类补充过程与近海资源数量变动的关系，为动态监测三峡工程对河口生态环境影响提供科学依据。     

Spatial distribution and vertical migrations of fish larvae communities off Northwestern Iberia sampled with LHPR and Bongo nets

The spatial distribution and diel vertical migration of fish larvae were studied in relation to the environmental conditions off NW Iberia during May 2002. Larvae from 23 families were identified, the most abundant were the Clupeidae, Gobiidae, Callionymidae, Blenniidae, Sparidae and Labridae. Sardina pilchardus was the most abundant species, mean concentrations 1 order of magnitude higher than the other fish larvae species. Larval horizontal distribution was mainly related to upwelling-driven circulation, resulting in an offshore increase of larval abundance while the vertical distribution was closely associated to the Western Iberia Buoyant Plume. Despite this general trend, taxon-specific relationships between the distribution of larvae and environmental variables were observed, and temperature was an important regressor explaining the distribution of most taxa. A comparison between ichthyoplankton samples collected alternatively with the LHPR and Bongo nets resulted in captures of larvae ≈1 order of magnitude higher for the LHPR, probably related to its higher towing speed. The spatial distribution and relative composition of larvae were also different for both nets, although the most frequent/abundant groups were the same. A fixed station sampled for 69-h showed diel vertical migrations performed by the larvae, with the highest larval concentrations occurring at surface layers during the night and most larvae being found in the neuston layer only during that period.     

The influence of physical and biological processes on the ichthyoplankton communities in the Gulf of Sirte (Southern Mediterranean Sea)

This paper reports on the first study on the ichthyoplankton community structure in the Gulf of Sirte and its spatial distribution in relation to environmental conditions and zooplankton abundance. The results make an important contribution to the future management of fisheries in this unexplored, but much exploited, area. Biological samples were collected in July 2008 using a Bongo40 net. In total, 1914 larvae were found and 1652 of these were identified. In particular, bathypelagic taxa were the most abundant, followed by demersal, mesopelagic, pelagic and epipelagic taxa. The ichthyoplankton community had a patchwork distribution influenced by oligotrophic conditions, the bottom depth and oceanographical features. The results suggest that environmental forcings were able to transport the ichthyoplankton to productive areas. Indeed, maximum fish egg densities were found in coastal stations in correspondence with the Atlantic Tunisian Current inflow, whereas larvae were mainly concentrated in the east side of the Gulf, probably as a result of advection by the anticyclonic circulation. Additionally, the distribution patterns of the total larvae density and the different assemblages were well matched with the abundance of the zooplankton, probably determining final larval survival, growth and recruitment.     

海蜇(Rhopilema esculentum)浮游幼体对褐牙鲆(Paralichthys olivaceus)卵和初孵仔鱼捕食的比较研究

利用实验生态学方法研究不同个体大小的海蜇浮游幼体[平均伞径(2.5±0.1),(4.1±0.2),(11.7±0.5),(21.1±0.6)mm]对不同密度(10,30,50,80ind/L)的褐牙鲆卵[卵径(0.92±0.01)mm]和初孵仔鱼[全长(3.01±0.08)mm]的捕食率,解析海蜇浮游幼体对初孵仔鱼的捕食率随捕食时间(0.5,1,2,3,4,5h)的变化特征。结果表明,各个体组海蜇浮游幼体对卵的捕食率均显著低于对仔鱼的捕食率;它们对卵的捕食率与卵密度和海蜇个体大小的关系不显著,但对仔鱼的捕食率随海蜇个体大小及仔鱼密度的增大而显著升高;伞径21.1mm的个体对仔鱼的捕食率在开始捕食后1h时达到最大值[17.3ind/(predator.h)],此后随捕食时间的延长而逐渐下降。在自然水域中,如果二者发生时空上的匹配关系,海蜇浮游幼体对仔鱼的捕食可能影响褐牙鲆的早期存活及其资源补充量的变动。     

长江口鱼卵仔鱼资源现状的调查与分析

根据2003年5月至2004年11月长江口海域7个航次、115个站次的鱼卵仔鱼调查采样资料分析,共鉴定出该海域的鱼卵仔鱼51种,隶属10目27科45属;其中,5种仅鉴定到科,4种仅鉴定到属,还有两种未能鉴定。在长江口门附近鱼卵较为集中,绝大部分为凤鲚鱼卵,占鱼卵总数的95.7%,其它小部分分别为鮻、斑点马鲛、长蛇鲻、中华小公鱼、小带鱼以及鲆科的鱼卵。中华小公鱼的仔鱼出现次数最多,占仔鱼总次数的38.4%;凤鲚、虎鱼科、棘头梅童鱼、鮻和斑鱼祭的仔鱼分别占仔鱼总次数的19.7%、14.4%、6.6%、6.2%和3.5%。长江口门内分布的主要仔鱼种类为凤鲚、赤鼻棱鱼是、中华小公鱼等;长江口门以外分布的主要仔鱼种类为凤鲚、鮻、鲆科、小黄鱼和长蛇鲻等;其中凤鲚、中华小公鱼等的仔鱼和鱼卵较多。5月鱼卵仔鱼的种类和数量较多,2月和11月的较少。与历史同期相比,该海域部分种仔鱼类已经消失,棘头梅童鱼等经济种类的鱼卵仔鱼资源补充量急剧下降,表明长江口海域经济种类仔鱼资源已受到衰竭的威胁。     

Potential transport of plaice eggs and larvae between two apparently self-contained populations in the Irish Sea

A coupled physics particle-tracking model, driven by realistic meteorological forcing was used to examine the dispersal and transport of plaice eggs and larvae in the year 2000 from two spawning grounds in the Irish Sea. The model included passive transport of eggs and early stage larvae, diel vertical movements for larvae between 7 and 10.5 mm in body-length and tidally synchronised, vertical movements for larger larvae (>9 mm body-length). The year 2000 was chosen because of the availability of ichthyoplankton data with which to initialise the model. The majority of larvae originating from spawning in the eastern Irish Sea settled into nursery grounds along the Scottish, English and Welsh coasts, in agreement with previous findings. In contrast, a significant portion of larvae originating from spawning in the western Irish Sea was transported eastwards to these same nursery grounds. Transport across the Irish Sea resulted from the onset of tidally synchronised vertical behaviour encoded in the model for older larvae. Settlement of larvae into local nursery grounds along the Irish coast was limited. Because of the prevailing winds and currents in the region, plaice eggs and larvae are unlikely to be transported from east to west; in most years spawning in the western Irish Sea probably acts as an additional source of juveniles for nursery grounds along the Scottish, English and Welsh coasts.     

Composition and ecological distribution of ichthyoplankton in eastern Beibu Gulf

Surveys were conducted in four seasons in the eastern Beibu Gulf from July 2006 to November 2007,to determine the ichthyoplankton composition,abundance,as well as environmental factors impacted on their spatiotemporal distributions.The fish eggs and larvae were sorted from 303 zooplankton quantitative samples,in which at least 1 order,60 families,31 genera and 61 species of fish eggs and larvae were identified.The species number was highest in summer whereas lowest in winter.With the most abundant fish egg (the average density was 2.41 ind./m 3),spring was the main spawning season,while the greatest mean density of fish larva was 1.35 ind./m 3 in summer.In the whole year around,fish eggs had the trends to aggregate in the nearshore of Guangxi coast,fish larvae were more abundant in the northern water.Relationships between fish eggs and larvae abundance and environmental factors were analyzed by using the Yield-Density model.The spatiotemporal distribution of ichthyoplankton in eastern Beibu Gulf was closely related to the Chl a concentration,and the optimal temperature,salinity and Chl a were 19.4-21.7 C,31.8-33.1 and 1.5-4.8 mg/m 3,respectively.Additionally,the distribution of fish larvae could be effected by ocean currents in summer and autumn.     

Seasonality of occurrence,foods and food preferences of ichthyoplankton in Biscayne Bay,Florida

Ichthyoplankton and microzooplankton were collected twice monthly for one year at a single station in Biscayne Bay, Florida. Based on approximate 10-m³, 333-μm mesh bongo net samples, the mean annual densities were 17·7 m^?3 and 1·8 m^?3 for fish eggs and larvae, respectively. Ichthyoplankton was most abundant in spring-summer. The most common fish larvae were bay anchovy (Anchoa mitchilli), spotted dragonet (Callionymus pauciradiatus), thread herring (Opisthonema oglinum) and gobies (Gobiidae), which comprised 50% of all larvae collected. A comparison of 35-μm and 333-μm mesh, bongo net collections revealed that mean densities of fish larvae were 8·5 times higher in the smaller mesh. The most abundant microzooplankton, based on 35-μm bongo net collections, were copepod nauplii, <100 μm in width, which averaged 90·41^?1 and tintinnids which averaged 168·51^?1. The mean density of microzooplankton <100 μm wide, potentially suitable food for first-feeding fish larvae, was 104·91^?1, exclusive of tintinnids, and 273·41^?1 including tintinninds. Excepting tintinnids, seasonal variability in microzooplankton abundance was low relative to that for ichthyoplankton. High microzooplankton densities, combined with low seasonal variability, indicated that feeding conditions for fish larvae were usually good in Biscayne Bay. Copepods, especially nauplii, were the predominant food of fish larvae (71% of all food items). Only mollusc veliger larvae (18% of all food items) were highly preferred prey but they were a small component of most larval fish diets. Average width of prey eaten by first-feeding larvae was 74 μm. Prey size increased in relation to larval length.     

Spatiotemporal distribution of fish eggs and larvae in the Huanghe(Yellow) River estuary,China in 2005–2016

Decreasing fish resources in estuaries is a subject of anthropogenic activities. Studies of the spatiotemporal distribution of fish eggs and larvae can help identify the status and processes underlying recruitment in a fishery. As the fifth largest river estuary in the world, the Huanghe (Yellow) River estuary (HRE) is a typical estuary that has been seriously aff ected by human activities. Annual surveys on ichthyoplankton and environmental factors were conducted in the months of May of 2005 and 2009-2016 in the HRE to investigate the spatiotemporal distribution of fish eggs and larvae and the associated infl uencing factors. A total of 23 and 20 species of eggs and larvae, respectively, were collected. The dominant orders were Perciformes (51.2%) and Clupeiformes (25.6%). The average number of fish species eggs and larvae were 6.0 and 4.1 in average abundance of 0.91 and 0.13 ind./m^3 , respectively. The dominant species were mainly low-commercial-value small-sized fishes, such as Clupanodon punctatus , Harengula zunasi, and Acanthogobius, whereas certain traditional commercial fishes, such as Trichiurus lepturus , and Clupea pallasii, were not seen. Analysis of the fish egg and larval community revealed four temporal assemblages and two spatial assemblages. Salinity was the main factor on the spatial distribution of ichthyoplankton communities, the species number and Shannon-Weiner diversity index (H′) of the fish egg and larval community near the river mouth with lower salinity were signifi cantly lower than the community far away from the river mouth with higher salinity. In addition, increases of water temperature promoted the number and abundance of fish species eggs, and the areas of abundant prey tended to have a more diversified and abundant of ichthyoplankton species. In overall, overfishing, dam construction, and other human activities were the main drivers that led to the substantial decline in fishery resources in the HRE.     

黄海中南部近岸海域春季鱼类浮游生物群落空间格局研究

根据2015年春季在黄海中南部近岸海域进行的鱼类浮游生物大型浮游生物网水平拖网数据,采用生态多样性指数和多元统计分析等方法,研究了该海域鱼类浮游生物的种类组成和群落空间格局及其与环境因子的关系。结果表明,本次调查共采集到鱼类浮游生物35种,其中鱼卵21种,仔稚鱼23种。鱼类浮游生物隶属于8目18科34属,优势种为鳀（Engraulis japonicus）、鲬（Platycephalus indicus）、鱼衔属（Callionymus spp.）和小黄鱼（Pseudosciaena polyactis）。其中,鳀和鱼衔属主要分布于海州湾渔场海域,鲬主要分布于吕泗渔场海域,小黄鱼多分布于吕泗渔场北部海域。生态类型包括半咸水型、沿岸型和近海型种类。聚类分析表明,鱼类浮游生物群落可划分为以鱼衔属、鳀为优势种的站位组A（主要分布于海州湾海域）、以小黄鱼、黄鲫（Setipinna taty）等为优势种的站位组B（主要位于江苏沿岸海域）和以鲬为优势种的站位组C（主要位于江苏沿岸-近海海域）,以站位组B的群落物种多样性指数和均匀度指数最高。各站位组的鱼类浮游生物的生态类型和适温类型组成不同,这与其所处的海域生境有关。典范对应分析（CCA）表明,影响春季黄海中南部鱼类浮游生物群落空间结构的主要环境因子为水深和表层温度。同时也受洋流、底质类型等多种因素的综合影响。研究结果初步揭示了黄海中南部近岸海域鱼类浮游生物群落的空间格局,可为今后科学制定该海域水产种质资源保护区、资源量化管理等资源养护管理措施提供科学依据与技术支撑。     

The distribution of life cycle stages of two deep-water pleuronectids,Dover sole (Microstomus pacificus) and rex sole (Glyptocephalus zachirus), at the northern extent of their range in the Gulf of Alaska

Dover sole (Microstomus pacificus) and rex sole (Glyptocephalus zachirus) are both commercially valuable, long-lived pleuronectids that are distributed widely throughout the North Pacific. While their ecology and life cycle have been described for southern stocks, few investigations have focused on these species at higher latitudes. We synthesized historical research survey data among critical developmental stages to determine the distribution of life cycle stages for both species in the northern Gulf of Alaska (GOA). Bottom trawl survey data from 1953 to 2004 (25 519 trawls) were used to characterize adult distribution during the non-spawning and spawning seasons, ichthyoplankton data from 1972 to 2003 (10 776 tows) were used to determine the spatial and vertical distribution of eggs and larvae, and small-meshed shrimp trawl survey data from 1972 to 2004 (6536 trawls) were used to characterize areas utilized by immature stages. During the non-spawning season, adult Dover sole and rex sole were widely distributed from the inner shelf to outer slope. While both species concentrated on the continental slope to spawn, Dover sole spawning areas were more geographically specific than rex sole. Although spawned in deep water, eggs of both species were found in surface waters near spawning areas. Dover sole larvae did not appear to have an organized migration from offshore spawning grounds toward coastal nursery areas, and our data indicated facultative settling to their juvenile habitat in winter. Rex sole larvae progressively moved cross-shelf toward shore as they grew from April to September, and larvae presumably settled in coastal nursery areas in the autumn. In contrast with studies in the southern end of their range, we found no evidence in the GOA that Dover or rex sole have pelagic larval stages longer than nine months; however, more sampling for large larvae is needed in winter offshore of the continental shelf as well as sampling for newly settled larvae over the shelf to verify an abbreviated pelagic larval stage for both species at the northern end of their range.     

Shelf spawning habitat of Emmelichthys nitidus in south-eastern Australia – Implications and suitability for egg-based biomass estimation

The spawning habitat of Emmelichthys nitidus (Emmelichthyidae) in south-eastern Australia is described from vertical ichthyoplankton samples collected along the shelf region off eastern through to south-western Tasmania during peak spawning in October 2005–06. Surveys covered eastern waters in 2005 (38.8–43.5°S), and both eastern and southern waters in 2006 (40.5°S around to 43.5°S off the south-west). Eggs (n = 10,393) and larvae (n = 378) occurred along eastern Tasmania in both years but were rare along southern waters south and westwards of 43.5°S in 2006. Peak egg abundances (1950–2640 per m⁻²) were obtained off north-eastern Tasmania (40.5–41.5°S) between the shelf break and 2.5 nm inshore from the break. Eggs were up to 5-days old, while nearly 95% of larvae were at the early preflexion stage, i.e. close to newly emerged. Average abundances of aged eggs pooled across each survey declined steadily from day-1 to day-5 eggs both in 2005 (97-18) and 2006 (175-34). Moreover, day-1 egg abundances were significantly greater 2.5 nm at either side of the break, including at the break, than in waters ≥5 nm both inshore and offshore from the break. These results, complemented with egg and larval data obtained in shelf waters off New South Wales (NSW; 35.0–37.7°S) in October 2002–03, indicate that the main spawning area of E. nitidus in south-eastern Australia lies between 35.5°S off southern NSW and 43.5°S off south-eastern Tasmania, and that spawning activity declines abruptly south and westwards of 43.5°S around to the south-west coast. In addition, quotient analyses of day-1 egg abundances point to a preferred spawning habitat contained predominantly within a 5 nm corridor along the shelf break, where waters are 125–325 m deep and median temperatures 13.5–14.0 °C. Spawning off eastern Tasmania is timed with the productivity outburst typical of the region during the austral spring, and the temperature increase from the mixing between the southwards advancing, warm East Australian Current and cooler subantarctic water over the shelf. Overall, ichthyoplankton data, coupled with reproductive information from adults trawled off Tasmania, indicate that E. nitidus constitutes a suitable species for the application of the daily egg production method (DEPM) to estimate spawning biomass. This finding, together with evidence in support of a discrete eastern spawning stock extending from southern NSW to southern Tasmania, strengthens the need for DEPM-based biomass estimates of E. nitidus prior to further fishery expansion.     

Japanese anchovy egg accumulation at the sea surface or pycnocline—Observations and model

Near surface vertical distributions of Japanese anchovy eggs (isolated and pelagic) were studied at western Wakasa Bay, Japan. Samples were collected in horizontal tows with four plankton nets simultaneously operated at different four depths of 0, 0.5, 1.0, and 2.0 m. The egg concentration was found to decrease exponentially with depth. The egg concentration profile can be explained by considering the balance of the eggs' ascent and vertical diffusion. Taking further into account vertical difference in rising/sinking rates of the eggs, a clear accumulation of the eggs on a pycnocline, observed elsewhere, also can be explained. Vertical eddy diffusivity in the surface layer in a calm sea was 1–10 cm² s^–1, as estimated from the egg concentration profile and the velocities of the eggs in the vertical direction.     

Mesozooplankton and ichthyoplankton distribution around Gran Canaria,an oceanic island in the NE Atlantic

In October 1991, mesozooplankton biomass and ichthyoplankton were studied in the waters surrounding the island of Gran Canaria (Canary Islands). The average dry weight obtained for mesozooplankton biomass (4.5 mg m⁻³) is typical of the area. Average fish egg abundance (94 eggs per 10 m²) was similar to that found previously for the Canary Current. However, the average fish larva abundance (904 individuals per 10 m²) was higher than previously recorded for the Canary Current and similar regions. The horizontal distributions of the planktonic components studied appear strongly related to the mesoscale oceanographic structures in the area. These included an area of weak flow around the stagnation point upstream of the island, where higher concentrations of neritic ichthyoplankton occurred, a warm lee region downstream, where mesozooplankton biomass and neritic ichthyoplankton were increased, particularly on the convergent anticyclonic boundary, and the offshore boundary of an upwelling filament from the NW African coast, which acted as a barrier for neritic ichthyoplankton. These concentrations suggest that the stagnation point and the lee are areas of retention for neritic fish eggs and larvae. Simple Lagrangian simulations of particle trajectories in the observed field of flow demonstrate the potential for retention of organisms, both passive and with limited swimming ability, in these areas. On the flanks of the island and in the filament, the simulation suggests even swimming organisms will be largely swept away. The various oceanographic structures, by increasing the planktonic production, are partially responsible for the relatively high values of abundance obtained for fish larvae.     

Variability in duration and intensity of euphausiid spawning off central Oregon, 1996–2001

We tracked the duration and intensity of the euphausiid spawning season through biweekly sampling along a transect off Newport, OR (latitude 44°40′N) over a six year period from 1996 to 2001. Our sampling consisted of vertical plankton tows, CTD casts, and collection of water for determination of chlorophyll a. Here, we report on data collected from two stations, 5 and 15 nautical miles (9.3 and 27.8 km) offshore. The density of euphausiid eggs in our samples was highly variable spatially and temporally; we saw the most striking differences in egg densities and length of the spawning season, when we compared spawning before and after 1999. This year corresponded to the time when the Pacific Decadal Oscillation switched from warm phase (pre-1999) to cool phase (1999–present). The years 1996 and 1997 were characterized by one large, late summer peak in egg density at our inshore station. 1998, an El Niño year, followed this pattern for our offshore station, but eggs were nearly absent at our inshore station. Starting in 1999, we saw multiple peaks in egg density and found that the spawning season extended from spring through early fall. For example, in spring (March–May) at the inshore station, the abundance of eggs increased from an average of 0.4 m⁻³ (1996–1998) to 51.3 m⁻³ (1999–2001), and for summer (July–September), 27.8 m⁻³ to 132.6 m⁻³ for the same time period. At the offshore station, egg abundances doubled over the same two time periods: 7 m⁻³ versus 11 m⁻³ (spring) and 55 m⁻³ versus 186 m⁻³ (summer). Peaks in egg densities were often associated with phytoplankton blooms, but not in a predictable way. Peaks in egg densities often followed cold-water upwelling events, especially at the inshore station. It is not yet clear whether this connection is due to changes in advection or changes in upwelling-induced productivity.     

黄河口近岸海域鱼卵、仔稚鱼种类组成及群落结构特征

为了解调水调沙期间黄河口及邻近海域鱼卵、仔稚鱼群落结构的动态变化,作者分别于2011年和2018年黄河调水调沙期间（6月—7月）,利用大型浮游生物网对该海域的鱼卵、仔稚鱼进行表层水平拖网调查。结果表明：2011年3个航次共采集鱼卵1 280粒,仔稚鱼5 973尾,隶属于7目11科13属;2018年3个航次共采集鱼卵4 104粒,仔稚鱼237尾,隶属于7目11科13属。优势种以斑鰶（Konosirus punctatus）、鳀（Engraulis japonicus）和赤鼻棱鳀（Thryssa kammalensis）等短生命周期、低营养层级的小型中上层鱼类为主。靠近黄河入海口处站位的鱼卵、仔稚鱼密度相对较高,鱼卵、仔稚鱼分布范围向黄河入海口门处集中。鱼卵、仔稚鱼的多样性指数在调水调沙过程中出现波动,过后又恢复至调水调沙前水平。环境因子Pearson相关性分析表明,鱼卵数量与环境因子间无显著相关性（P0.05）,仔稚鱼数量与叶绿素a的含量呈极显著正相关（R=0.870,P<0.01）。两个年度调查结果对比发现,总体来说调查期间黄河口及邻近海域鱼卵、仔稚鱼种类数变化不大,在适温类型组成上均以暖温种为主;2018年鱼卵、仔稚鱼采集数量均小于2011年,但是鱼卵、仔稚鱼的均匀度指数（J’）和多样性指数（H’）均大于2011年,除6月上旬航次外,其他两个航次丰富度指数（D）也均大于2011年。本研究补充了黄河口及邻近海域鱼类早期补充资源的基础数据,旨为黄河口邻近海域及渤海的渔业资源评估和养护提供依据。     

温度、光照及仔鱼个体大小对稚海蜇(Rhopilema esculentum)捕食褐牙鲆(Paralichthys olivaceus) 仔鱼的影响

利用实验生态学方法,研究温度(15、19和23℃)、光照(明和暗)、仔鱼大小[全长(3.01±0.08)mm初孵仔鱼和(3.79±0.13)mm孵化后5天仔鱼]对稚海蜇[伞径(21.1±0.4)mm]捕食褐牙鲆仔鱼的影响。结果表明,稚海蜇对初孵仔鱼的捕食率随着水温升高而显著升高。光照条件在各仔鱼密度(10,30,50和80ind/L)下均不显著影响稚海蜇对初孵仔鱼的捕食率,说明光条件并不显著改善稚海蜇捕食仔鱼的能力。在高仔鱼密度(50和80ind/L)下,稚海蜇对孵化后5天仔鱼的捕食率显著低于对初孵仔鱼的捕食率;但在低密度(10和30ind/L)下,稚海蜇对两个不同发育阶段仔鱼的捕食率之间无显著差异。在低仔鱼密度下,稚海蜇对仔鱼的捕食率较低,这会降低仔鱼个体大小对稚海蜇捕食率作用的显著性。这既表明仔鱼逃避被稚海蜇捕食的能力随其发育生长而提高,也反映了稚海蜇对不同个体大小仔鱼捕食作用受仔鱼密度制约。     

Morphology ofSagitta elegans (Chaetognatha) in early larval stages

Spawned eggs and newly-hatched larvae ofSagitta elegans were obtained by rearing the species in the laboratory.The eggs immediately after spawning are spherical, about 0.3 mm in diameter, and mostly in such an advanced state that an embryo in the egg can be easily seen through the membrane. The embryo is found enclosed within the egg, with the tail overlapping the head.The body length (from the tip of the head to the base of the tail) of larvae, newly-hatched to 2-days old, ranged from 1.23 to 1.42 mm long in 6 individuals. The larva is provided with a pair of posterior fins, but not yet furnished with the anterior fin: the existence of eye pigments cannot be confirmed for the thick collarette extending nearly all over the body; no hooks are developed yet; the median vertical septum is found already in the posterior portion of the body, though the tail septum is not yet formed.Through the rearing of larvae for 12 days, it was found that seven-day old larvae, 1.47–1.65 mm in length, were mostly provided with the tail septum, but with neither hooks nor eyes, while eight to eleven-day old larvae, 1.69–2.20 mm in length, were furnished with eight hooks on each side, but still without eyes observable on the dorsal surface of the head. These features indicate that the early morphological development of the species is similar to that ofSagitta crassa.Needless to say, but the tail-segment defined in these larvae is incomparably longer than in adults, as seen generally throughout the Chaetognatha.Based on a dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Fisheries Science at Hokkaido University in 1973.     

Geographical variation in abundance of striped and common dolphins of the western Mediterranean

Line-transect data from sighting surveys conducted in the western Mediterranean (in 1991) and the Alboran Sea (in 1992) were analysed to estimate densities and numbers of striped and common dolphins in various areas of the western Mediterranean. Density of striped dolphins in the northwestern Mediterranean was estimated as 0.20 dolphins km⁻² (CV = 0.24; 95% CI = 0.12 and 0.32) and was 41% higher than in the southwestern Mediterranean, where it was estimated as 0.12 dolphins km⁻² (CV = 0.38; 95% CI = 0.05 and 0.25). The highest densities were observed in the Liguro–Provençal basin, with 0.24 dolphins km⁻² (CV = 0.26; 95% CI = 0.14 and 0.40), and the Alboran Sea, with 0.20 dolphins km⁻² (CV = 0.33; 95% CI = 0.10 and 0.36). These areas, and especially the Ligurian Sea, appear to be the most productive in terms of the food consumed by striped dolphins. Common dolphins were abundant only in the Alboran Sea with an estimated density of 0.16 dolphins km⁻² (CV = 0.40; 95% CI = 0.08 and 0.35), scarce in the south Balearic area and almost absent in the northwestern Mediterranean. The magnitude of the dolphin by-catch in fishing operations in the Alboran Sea and other areas stresses the need for further assessment of densities and numbers, notably in the Alboran Sea and the North African Mediterranean waters.