Spawning movements of humpback whitefish in interior Alaska rivers

This study was conducted to describe the spawning movements and identify spawning areas for humpback whitefish Coregonus pidschian in the Minto Flats–Chatanika River complex, Alaska, during 2008 and 2009. Radio transmitters were surgically implanted in humpback whitefish in 2008 (N = 60) and 2009 (N = 100), and fish positions were determined through a combination of boat and aerial surveys and fixed receiving stations. Two spawning areas were identified: one in the Chatanika River downstream of the Elliot Highway Bridge and the other in the Tanana River near Fairbanks. Humpback whitefish dispersed from the wetland complex of Minto Flats in June, moved upstream through late August, arrived at the spawning areas in early September and began moving downstream in early October. In 2009, spatially segregated movements were observed when approximately 40% of the radio‐tagged humpback whitefish moved to the Tanana River, suggesting that humpback whitefish in Minto Flats are comprised of mixed spawning stocks. These study results provide a complete account of humpback whitefish movements and their associated spawning habitats, which will allow for better‐informed management strategies.     

Allochrony as a potential driver for reproductive isolation in adaptive radiations of European whitefish ecomorphs

In northern Fennoscandian lakes, monophylogenetic lineages of postglacial fishes are radiating into several adaptive forms, but the speciation process is still at an incipient stage. The speciation process has received increased attention over the years, but the underlying mechanisms and drivers are still debated and poorly understood. European whitefish (Coregonus lavaretus [L.]) is the most abundant fish species in these lakes and has evolved into several ecomorphs adapted to different trophic niches and habitats. Genetic divergence has been observed among these ecomorphs, but the mechanism(s) responsible for the ongoing build-up of reproductive isolation has still to be revealed. As these systems are young in evolutionary time (<10 kyr), prezygotic and postzygotic extrinsic isolation mechanisms are thought to be more likely to contribute to the reproductive isolation than intrinsic isolation mechanisms. We determined the gonadosomatic index (GSI) of three ecomorphs in two replicated lake systems and used GSI as a proxy to investigate the prezygotic isolation mechanism, allochrony, as a driving factor of divergence in this adaptive radiation of whitefish. We found that the three ecomorphs differed in GSI values within and between lakes, suggesting different spawning times of the ecomorphs. We also show that males of one ecomorph had equal onset of maturity as another ecomorph, giving novel insights into the ongoing gene flow observed between ecomorphs. The result supports allochrony as a driver for the divergence process of whitefish ecomorphs, but more evidence is still needed to rule out that the three ecomorphs make use of different spawning grounds.     

棘胸蛙产卵量、卵子孵化率的比较研究

为选择适于闽北的棘胸蛙养殖品种,比较了异地引种棘胸蛙和本地引种棘胸蛙的产卵量和卵子孵化率。试验表明,异地经过几个世代驯化的棘胸蛙在总产卵量上要比本地引种的棘胸蛙要多两倍多,产卵总数为3071枚,本地引种的棘胸蛙产卵总数为863枚。异地引种棘胸蛙在卵子孵化率上也比本地引种棘胸蛙要高,平均为95.3%,而本地引种的棘胸蛙的卵子孵化率仅为64.18%,说明异地引种的棘胸蛙在闽北有较好的推广前景。     

不同茭白品种福寿螺卵块分布及竹片诱螺产卵效果

为了研究控制茭白田福寿螺种群的方法,本文在调查不同茭白品种上福寿螺卵块分布差异基础上,开展不同规格(3、6、9 cm宽)竹片诱集福寿螺产卵试验。结果显示,不同茭白品种上福寿螺卵块分布数量差异大,单季茭白品种以‘杭州一点红’上卵块最多(11.6个/丛),远高于其他9个品种,最少的是‘八月茭’‘金茭1号’(分别为1.7、2.3个/丛)。双季茭白品种间的差异不显著,每个茭白品种上的卵块数在5.1~7.4个之间。不同规格竹片对福寿螺的产卵诱集效果差异大,引诱效果最好的为9 cm规格的竹片效果最差的是3 cm规格竹片。竹片凸面诱集到的卵块较多,凹面诱集到的卵块很少,竹片凸面朝田埂方向插入诱集产卵效果更好。福寿螺的产卵高度呈正态分布,主要集中在20~40 cm之间,未发现有靠近水面或在水下的卵块,卵块大小与数量呈线性正相关。研究结果为利用竹片诱集茭白田福寿螺产卵提供了技术依据。     

Confirmation of the spawning area of the striped marlin, Tetrapturus audax, in the so-called core area of the eastern tropical Pacific off Mexico

We report the presence of striped marlin larvae in coastal waters of the mouth of the Gulf of California, collected during seven oceanographic cruises during 1990 to 1993. From 169 sampled stations, 30 produced a total of 68 larvae of 2.4–30.5 mm total length. Most of the larvae were about 3 mm, indicating a recent spawn. The sea surface temperature at the sampled stations ranged from 19.4°C to 32.0°C, but larvae were caught at stations with temperatures between 27.8°C and 31.5°C. These results clarify the existence of a spawning area of striped marlin in the eastern Pacific, located closer to the coast than previously believed, during several months of the year.     

Larval transport during winter in the SABRE study area: results of a coupled vertical larval behaviour–three-dimensional circulation model

A three-dimensional circulation model was used in conjunction with larval fish vertical behaviour models to study the interaction between larval vertical distribution, advection and the outcome of larval transport along the central portion of the east coast of the United States. The circulation model was forced by tides, a northern boundary inflow, and winds. Vertical behaviour models were developed for Atlantic menhaden ( Brevoortia tyrannus ) and spot ( Leiostomus xanthurus ). The purpose of this modelling effort was to investigate the transport pathways of Atlantic menhaden and spot larvae from offshore spawning grounds to estuarine nursery habitats. The coupled circulation and behavioural model demonstrated the importance of along-shelf transport in what is generally thought to be a 'cross-shelf' problem. Cross-shelf transport was associated with bathymetric features, such as shoals. Both physical (e.g. wind) and biological (e.g. changes in larval behaviour) events were responsible for many of the observed patterns in larval transport. Overall, larval transport was determined by circulation but was modified by larval vertical distributions.     

The onset of spawning in the silver pomfret, Pampus argenteus (Euphrasen), in Kuwait waters and its implications for management

Abstract The spawning periodicity of silver pomfret, Pampus argenteus (Euphrasen), was investigated against a background of conflicting evidence on the onset of spawning in this species. Contrary to the existing view that silver pomfret in Kuwait waters begin to spawn in March–April, evidence is presented that indicates a delay in spawning until May. Only an insignificant level of spawning takes place in April which, from the management point of view, may be ignored. The species has a prolonged spawning period extending from May to August in females, although the males mature in April and ripe specimens are encountered in monthly samples until September. There are two spawning peaks, the first one in May and the second in August.     

Oceanographic influences on the distribution of Baltic cod, Gadus morhua, during spawning in the Bornholm Basin of the Baltic Sea

The Baltic Sea is a stratified, semienclosed sea typified by a low-salinity surface layer and a deep saline layer of varying volume, salinity, temperature and oxygen concentration. The relationships between these oceanographic factors and the distribution of Baltic cod are presented, utilizing results from a survey carried out during the 1995 spawning period in the Bornholm Basin, at present the main spawning area of this stock. Cod distribution, abundance and population structure were estimated from hydroacoustic and trawl data and related to hydrographic parameters as well as to bottom depth. In the central basin, cod were aggregated in an intermediate layer about 15 m thick. This area of peak abundance was defined at its upper limit by the halocline and at the lower limit by oxygen content. The majority of individuals caught in the basin centre were in spawning or pre-spawning condition with a high proportion of males to females. On the basin slopes, aggregations of cod were found near the bottom. These individuals were mainly immature and maturing stages with an increasing proportion of females to males with size. Salinity and oxygen conditions were found to be the major factors influencing the vertical and horizontal distribution of adult cod. Abundance of immature cod was also positively related to decreasing bottom depths. The effect of temperature was minor. The observed size- and sex-dependent spawning aggregation patterns, in association with habitat volume and stock size, may influence cod catchability and thereby the assessment and exploitation patterns of this stock.     

Broodstock spawning and larviculture of whiting (Merlangius merlangus L.) reared in captivity

In recent years, an increasing interest in the farming of marine ‘white’ fish, such as cod, has been observed in the aquaculture industry. One species being considered for aquaculture development is whiting (Merlangius merlangus L.). With little data being available on the domestication of this species, our study aimed to characterize spawning behaviour and rhythmicity in captive broodstock and provide original data on egg incubation, embryonic development and larval rearing. The results observed through video recording showed that spawning mainly occurred at night with active courtship behaviour. Daily egg batches were collected from two separate spawning seasons, with an average fertilization success declining from 77% to 53%. Time to hatch was inversely related to the incubation temperature and occurred after 78 degree‐days (9 days at 8 °C), with emerging larvae ranging in size from 3.3 to 3.46 mm total length and hatch success ranging from 48.3% to 99.9%. In comparison with a clear water environment, a green water regime during the first days of larval rearing significantly improved larval growth and survival. These results are the first to describe spawning activity, early development and larval performances in whiting and are promising for the potential future development of whiting aquaculture.     

伊洛河黄河鲤天然产卵场渔业水质评价

2004-2009年5-8月对伊洛河黄河鲤（Cyprinus carpio haematoperus）天然产卵场水体中的TN、TP等营养盐和WT、pH、DO、CODMn、挥发酚、Cu、Zn、Pb、Cd和Hg等理化指标进行了为期6年的连续监测,对该水域水质的年代变化趋势和质量状况进行了研究和综合评价。结果表明,黄河鲤天然...