Distribution patterns of larval myctophid fish assemblages in the subtropical–tropical waters of the western North Pacific

We examined larval myctophid fish assemblages and their distribution patterns, based on discrete depth sampling. Samples were collected at 19 stations along a transect that crossed the subtropical–tropical waters of the western North Pacific. In total, we collected 27 189 larvae of 40 myctophid species or types, belonging to 15 genera. Three assemblages were recognized, based on their species composition: Kuroshio Axis (KuA), Kuroshio Countercurrent (KCC), and Subtropical Countercurrent–North Equatorial Current (SCC–NEC) assemblages. The distributions of these assemblages were well defined by the positions of the KuA and the Subtropical Convergence. Each species had a specific distribution depth, and none showed diel vertical migration. Larvae of the subfamily Lampanyctinae were distributed in shallower waters (0–50 m) than larvae of the subfamily Myctophinae (50–150 m). Larvae of the same species were distributed at lower depths in the SCC–NEC area than in the KCC area. This corresponded to the abundance of chlorophyll a, which would reflect abundance of prey organisms such as copepod nauplii and copepodites.     

Fish larvae distribution off Mejillones Peninsula (northern Chile) during a coastal upwelling event in Spring 1999: interactions with the cold upwelling plume

We examined the interaction between vertical and horizontal distribution of fish larvae off Mejillones Peninsula (23°S), northern Chile, under conditions of active coastal upwelling. An oceanographic survey covered spatial variability in temperature, chlorophyll- a (chl a ), dissolved oxygen, salinity and water density. Fish larvae were sampled during daytime and nighttime periods through two consecutive days in four stations: two inside and two outside of a well-developed upwelling plume, and at three depth strata: 0–20, 20–80 and 80–200 m. Eighteen taxa were analysed, of which the Myctophidae Diogenychthys atlanticus , Diogenichthys laternatus , and the anchovy Engraulis ringens , were most abundant. Our data showed little evidence for diel vertical migration and larvae were more abundant at depth (>80 m) under low temperature (∼12°C) and low chl a (∼2 mg m^–3), below the highly advective upper layer. The exploratory K -means analysis allowed the separation of data into two distinct habitats: upwelling and nonupwelling types. Most taxa were allocated in nonupwelling waters, i.e. outside the cold plume. However, short-term variations (<24 h) in the position of the upwelling plume influenced both horizontal and vertical occurrence as well as abundance of taxa, and caused variability in temperature, oxygen and chl a . These changes in oceanographic conditions, caused by upwelling circulation and the dynamics of the cold plume, may sharply modify the habitat of fish larvae and have an important role in survivorship and recruitment success.     

Vertical distribution of jack mackerel Trachurus japonicus larvae in the southern part of the East China Sea

ABSTRACT:   The vertical distribution of jack mackerel Trachurus japonicus larvae was described based on discrete depth sampling using a MTD net system from the surface down to 100 m depth at 13 stations in the southern East China Sea between 27 February and 10 March 2002. Of the 20 782 fish larvae collected, T. japonicus larvae were most abundant, accounting for 37.0% of the total catch. The average abundance of the larvae was 419.0 individuals/10 m², with the average (± standard deviation [SD]) body length of 2.6 ± 0.3 mm (range 1.8–7.5 mm). The larvae were concentrated in the mixed layer, with peak densities in the 10–30 m layer. The average (±SD) weighted mean depth was 21.5 ± 7.8 m. There was no evidence of either diel or ontogenetic vertical migration for the early larvae of <5 mm. More than 90% of the T. japonicus larvae were collected in the water temperature ranging from 21 to 23°C. Vertical profiles of the larval densities and chlorophyll a coincided with each other, which might reflect the abundance of their main prey organisms, copepod nauplii and copepodites, since copepod production is known to be closely related with the chlorophyll a concentration.     

Annual changes in distribution depths of bighand thornyhead <Emphasis Type="Italic">Sebastolobus macrochir</Emphasis> off the Pacific coast of northern Honshu,Japan

ABSTRACT:   Body size dependent distribution patterns of bighand thornyhead Sebastolobus macrochir were examined using bottom trawl surveys in the Tohoku area, off the Pacific coast of northern Honshu, Japan. In northern and southern Tohoku, distribution depths of ≤10-cm standard length (SL) fish increased from 500–600 m in 2003 to 600–700 m in 2005 with an increase in density of 11–20-cm SL fish at depths of 500–600 m. In 2004–2005, small fish (≤10 cm SL) were distributed in deeper waters than large fish (11–20 cm SL). In ≤20-cm SL fish, the main distribution depths changed from 300–600 m in 1997–2002 to 500–600 m in 2003 in southern Tohoku, but not in northern Tohoku. Stepwise multiple regression analysis showed that negative correlations were found in biomass densities between a few demersal fish species and bighand thornyhead at depths of 300–400 and 400–500 m in southern Tohoku. These results suggest that distribution of bighand thornyhead was affected by intra- and interspecific competitions in the Tohoku area.     

The relationship between stock and catch and the effect of bait on catch as determined for a UK recreational catch and release fishery

Abstract Twelve anglers fishing in a UK navigation canal for a total of 42 h caught 567 fish, mainly gudgeon, Gobio gobio (L.) ( n =306) and roach, Rutilus rutilus (L.) ( n =253) at an average catch rate of 13.4 fish angler-h⁻¹ or 128.5 g angler-h⁻¹. The species and size of fish caught were compared with the numbers determined by depletion estimates at six sections of canal using micromesh seine netting. Fifty four percent of fish caught in the net were < 60 mm FL. Gudgeon (60–99 mm) were over-represented in the anglers' catches whilst roach (60–99 mm) were under-represented. The size distribution of roach and gudgeon caught by anglers using two types of bait (small maggots and chironomid larvae) was examined and smaller fish were found to be caught using the latter.     

长江中游黄石江段三种不同类型河道中仔鱼空间分布研究

2016年6月10-15日对长江中游黄石江段三种不同类型河道(分汊型、顺直型和弯曲型)中仔鱼的空间格局进行了研究。共采集仔鱼12 331尾,隶属于5目7科25种,优势种为贝氏(Hemiculter bleekeri)(占仔鱼总数的89.4%)、鳊(Parabramis pekinensis)(占4.6%)和吻虾虎鱼属(Rhinogobius sp.)(占1.6%)。弯曲型河道仔鱼平均密度最大,为(2.34±1.10)ind/m~3;分汊型河道次之,为(1.97±2.03)ind/m~3,顺直型河道最低,为(1.79±1.19)ind/m~3。三种河道类型的仔鱼总体空间分布特征相似,在水平分布上,近岸处仔鱼密度最高(3.06±1.54)ind/m~3,江心最低(1.16±0.94)ind/m~3;垂直分布上,仔鱼密度表层(3.20±2.51)ind/m~3最高,其次为中层(1.69±1.35)ind/m~3,底层最低(1.20±1.20)ind/m~3。不同发育阶段的仔鱼分布呈现一定规律,总体上仔鱼从卵黄吸尽期开始倾向于分布在近岸处浅水区。本研究表明分汊型和弯曲型河道中的近岸水域是鱼类育幼场的主要分布区,在航道整治等涉水工程的建设中应该予以重点保护。     

The effect of depth, distance from dam and habitat on spatial distribution of fish in an artificial reservoir

Abstract –  Spatial distribution of the fish community in the deep canyon-shaped Římov Reservoir, Czech Republic, was studied using overnight gillnetting fishing in 1999–2007. Effects of depth, distance from the dam to the tributary and habitat type (benthic and pelagic) on fish community structure, catch per unit of effort (CPUE), biomass per unit of effort (BPUE) and average weight were tested. Fish were recorded in all sampled depths and parts of the reservoir. Redundancy analysis revealed that effects of three environmental variables were significant and most variability was explained by depth, then by distance from the dam and habitat type. CPUE and BPUE of all species decreased with depth and responses of individual species to depth were similar for juvenile and adult fish. Number of species, CPUE and BPUE of all species except perch increased heading towards the tributary and peaked close to or at the tributary part of the reservoir. Responses of juvenile fish to distance from the dam differed from that of adult fish. Structure of fish community differed in benthic and pelagic habitats with species preferably occupying epipelagic (bleak, asp, rudd and juvenile bleak, roach and bream) or littoral waters (perch, pikeperch, ruffe, roach, bream and juvenile percids). This study showed that fish distribution in the reservoir followed distinct patterns, which were probably shaped by a combination of physiological constraints plus trade-off between food resources and competition.     

Growth and habitat of spotted halibut Verasper variegatus in the shallow coastal nursery area, Shimabara Peninsula in Ariake Bay, Japan

ABSTRACT:   To determine the growth performances and habitat characteristics of spotted halibut Verasper variegatus , successive samplings were conducted in the south-eastern coastal area of Shimabara Peninsula in Ariake Bay. The push-net samplings were performed at Kamaga beach from May 2003 to April 2004 to determine the horizontal distribution of larvae and juveniles, while the gill net samplings were done in the coastal waters of Tatsuishi beach from July 2003 to July 2004 to collect the larger juveniles and adults. A total of 478 individuals from metamorphosing larvae to 2-year-old fish (15.2–447.0 mm total length [TL]) were sampled. In particular, the 2003-year class fish were successively collected from May 2003 to June 2004 (15.2–350.0 mm TL; n  = 418) and the mean total length in March, June, September, December 2003 and May 2004 was 22.4, 82.5, 172.5, 203.9 and 296.4 mm, respectively. The present study found that metamorphosing larvae migrated into the estuarine tidal flats during March 2003; newly settled juveniles inhabited the shallow intertidal areas; and juveniles had a remarkably high growth in shallow coastal areas. It is suggested that young fish around 300 mm TL migrated from the nursery grounds in Ariake Bay to deeper waters around Tachibana Bay during May–June 2004.     

Late winter larval mesopelagic fish assemblage in the Kuroshio waters of the western North Pacific

The larval mesopelagic fish assemblage and its distribution patterns were investigated in the Kuroshio region off southern Japan in late winter. A total of 8690 fish larvae was collected, 85.8% of which were mesopelagic fish larvae. Mesopelagic fish larvae were significantly more abundant in the area east of the Kuroshio axis than west of the Kuroshio axis (660.6 versus 194.5 ind 10 m^?2). Sigmops gracile, Bathylagus ochotensis, Notoscopelus japonicus, Diaphus slender type and Myctophum asperum were the five most abundant larvae and accounted for 16.9, 16.4, 15.2, 13.9 and 9.3% of the total catch in numbers, respectively. We conclude that these larvae were transported by the Kuroshio Current to the more productive transition waters, where they spend their juvenile stage from spring to early summer. The possibility of expatriation and southward long‐distance spawning migrations of N. japonicus and B. ochotensis are discussed, based on the geographic distribution patterns of their larvae, juveniles and adults.     

Effects on growth and survival of loach (Misgurnus anguillicaudatus) larvae when co-fed on live and microparticle diets

The effectiveness of co-feeding loach ( Misgurnus anguillicaudatus ) larvae with live and microparticle diets on weaning performance was described here. Dry weight, total length, length and weight-specific growth rate (SGR) and survivals were monitored at 23–25 °C from the 4th day post hatching (dph) in different diet regimes, which included: microparticle diets (A), live cladocerans (B), enriched cladocerans (C), half microparticle diets plus half live cladocerans (D) and half microparticle diets plus half enriched cladocerans (E). The SGR (L and W) were significantly lower in treatment A than in other treatments after completing metamorphosis (day 4–20, P <0.05). On 30 dph, dry weight (mg) and total length (mm) were significantly lower in treatment A than in other treatments ( P <0.05). There were no significant differences in growth in treatments B, C, D and E before 30 dph. However, when live feed was withdrawn from 31–60 dph, in metamorphosed fish, there were significant differences ( P <0.05) among the treatments in survival and growth. Metamorphosed fish in treatment E had higher survival than the fish in other treatments at the end of the experiment. The SGR (L and W) of weaned fish in treatments B and C were similar but lower than in treatments A, D and E respectively. However, dry weight and total length in treatment A were significantly lower than in treatments D and E. It is suggested that weaning of M. anguillicaudatus from early development would appear to be feasible and that larval co-feeding improves the growth and the survival.     

Vertical distribution patterns of zooplanktivorous fish in a shallow, eutrophic lake, mediated by water transparency

Abstract –  The vertical distribution pattern (VDP) of fish at shallow sites in eutrophic lake – Lake IJssel, the Netherlands – as affected by water transparency, was examined. The pattern was assessed by pair trawling at three depths and by hydroacoustics from June to August. Water transparency was estimated by light intensity and Secchi depth measurements. Hydroacoustics showed that fish were more dispersed at night than during the day. European smelt, ( Osmerus eperlanus ) and young-of-the-year Eurasian perch ( Perca fluviatilis ) comprised 97% of the fish in numbers. European smelt concentrated near the surface, at light intensities of >200 µW · cm⁻² when the water was turbid, and near the bottom when the water was clear (Secchi depth > 1.2 m). We concluded that low water transparency over-ruled the light sensitivity of European smelt, and caused European smelt to stay higher in the water column.     

罗源湾夏季鱼卵和仔稚鱼种类组成与数量分布

分析研究了2009年7月福建罗源湾鱼卵、仔稚鱼的种类组成及数量分布。共鉴定19种鱼类的鱼卵和仔稚鱼,隶属于13科。其中,鱼卵10种、仔稚鱼14种。夏季,罗源湾水平拖网鱼卵和仔稚鱼平均密度分别为1.80 ind/m3和0.54 ind/m3;垂直拖网鱼卵和仔稚鱼平均密度分别为4.11 ind/m3和2.63 ind/m3。鱼卵、仔稚鱼以鳀科数量最多,优势种类为中颌棱鳀(Thrissa mystax)和康氏小公鱼(Stolephoruscommersonli)。与历史资料相比,不但种类数减少,且优势种由多科鱼类并存向鳀科鱼类为主转变。夏季鱼卵、仔稚鱼主要分布在罗源湾中北部海域及湾口附近。     

Assemblages of vertical migratory mesopelagic fish in the transitional region of the western North Pacific

Assemblages of vertical migratory mesopelagic fish are described for the nighttime upper 20 m layer of the transitional and adjacent waters in the western North Pacific. Twenty-three mesopelagic fish species belonging to six families and 16 genera were collected during June 1996. Family Myctophidae was most speciose, represented by 17 species, followed by Sternoptychidae (two spp.) and Bathylagidae (one spp.). Six assemblages are recognized based on their species composition: Subarctic, Northern Transition, Southern Transition, Subtropical, Slope Water and Seamount Assemblages. These assemblages are also characterized by size composition and biomass of the catches. The distributions of the Subarctic, Northern Transition, Southern Transition and Subtropical Assemblages are approximately defined by the Kuroshio and Oyashio fronts and the Subarctic Boundary. Slope Water and Seamount Assemblages are closely related to the slope water around the shelf edge off Japan and waters around the Shatsky Rise and the Emperor Seamount chain, respectively. The importance of the Southern Transition Assemblage area between the Kuroshio front and Subarctic Boundary as spawning and nursery grounds of many subarctic, transitional and subtropical fishes is elucidated, based on the geographical distribution patterns of their larvae and juveniles.     

Depth, temperature and salinity preferences of newly recruited penaeid shrimps in Kuwait waters

Associations between catches and depth, temperature and salinity data obtained from the 1994–97 preseason shrimp trawl surveys in Kuwait waters were analysed using cumulative distribution functions and overlap coefficients. No single environmental factor had a controlling influence on shrimp distribution. Shrimp associations with the joint distributions of two environmental variables were stronger and more consistent over time than those with any single environmental factor. All three shrimp species examined in this study were significantly associated with the joint distributions of depth and temperature, and depth and salinity, indicating depth as the most influential factor in structuring the shrimp distributions during the surveys. Metapenaeus affinis and Parapenaeopsis stylifera were distributed at similar ranges of depth (8–15 m), temperature (26–31°C) and salinity (35–41‰), and had very high overlap coefficients. These two species can be categorized as co-occurring species in the sampled area. Penaeus semisulcatus had the widest range of the three environmental variables investigated in this study, particularly depth (8–32 m) and temperature (24–32°C).     

莱州湾大型砂壳纤毛虫丰度的水平分布

根据2011年5-11月及2012年3-4月在莱州湾进行的每月1次共9个航次的调查资料,通过解剖镜下镜检浮游生物网拖网样品,分析莱州湾3-11月大型砂壳纤毛虫丰度的水平分布。结果显示,砂壳纤毛虫总丰度的水平分布在不同时间呈现不同的特点:3–5月砂壳纤毛虫总丰度在湾底较高,向湾口递减;6-11月砂壳纤毛虫总丰度在湾中及湾口较高,湾底近岸海区较低。各月砂壳纤毛虫丰度较大的区域温度、盐度比较相似,表明砂壳纤毛虫可能有一定的适温性和适盐性。其中,6月砂壳纤毛虫丰度的分布与同期调查的鱼卵和仔稚鱼的分布较一致,表明砂壳纤毛虫可能是仔稚鱼的开口饵料,对鱼类仔稚鱼的成活和发育有帮助。3-11月砂壳纤毛虫种丰富度的变化范围是5-20种,有17个种在不同月份成为优势种。优势种种类数最多的是7、8月(10种),4月最少(2种)。各航次中不同优势种的最大丰度为489×103个/m3(运动类铃虫Codonellopsis mobilis,5月);较小的丰度仅为4×103个/m3(半旋拟铃虫Tintinnopsis hemispiralis,11月)。主要优势种(连续3个月或3个月以上为优势种的种类)有运动类铃虫(C.mobilis)、白领细壳虫(Stenosemella nivalis)、根状拟铃虫(Tintinnopsis radix)、妥肯丁拟铃虫(T.tocantinensis)和半旋拟铃虫(T.hemispiralis)。8月在黄河入海口附近的3个站位发现河口拟铃虫(Tintinnopsis estuariensis),这是在长江口海域发现的砂壳纤毛虫新种。     

Larval feeding behaviour of the endangered fish golden bubblebee goodeid, Allotoca dugesi, implications for conservation of an endangered species

Abstract To improve survival of cultured juvenile fishes, it is important to understand prey preferences and predation behaviour of fish larvae. In this study, the feeding behaviour and prey preference of Allotoca dugesi (Bean), a small fish species endemic to Mexico and currently threatened with extinction are presented. Three zooplanktonic prey, viz. Brachionus calyciflorus (Pallas) , Moina macrocopa (Goulden) and Daphnia pulex (Leydig) were tested. The mean size (standard length ± SE, mm) of the larvae ranged from 9.0 ± 0.1 mm at week 1 to 18 ± 2 mm at the end of the experimental period (8 weeks). The gape size (mean ± SE) increased from 0.125 ± 0.002 mm at the first week to 2.300 ± 0.361 mm by the eighth week. Capture success (capture/attack) ranged from 0.80 to 0.98 with Brachionus , 0.72–0.94 with Moina and 0.17–0.46 with Daphnia . Prey preference experiments were conducted using B. calyciflorus, M. macrocopa and D. pulex at a fixed ratio of 5 : 2 : 2 ind. mL⁻¹, respectively, and revealed a positive selection for rotifers and Moina , but avoidance of Daphnia . The results are discussed with reference to conservation efforts for Allotoca dugesi .     

Growth of pike larvae (Esox lucius) under different conditions of food quality and salinity

Abstract –  We measured growth of pike larvae ( Esox lucius ) fed with freshwater and brackish-water zooplankton by monitoring larval wet weight during 18 days. The fish food was analysed for species composition, carbon, nitrogen and fatty acids. Further, we analysed fish larval faecal pellet production. Larval weight was significantly higher in fresh water than in brackish water with natural zooplankton as food. Growth, given as wet weight, showed a significant relationship with zooplankton (>100  μ m) food carbon and highly unsaturated fatty acids, 20:5ω3, 22:6ω3, ω6 fatty acids and the ω3/ω6 fatty acid ratio. Phytoplankton fatty acids (10–50  μ m), such as polyunsaturated fatty acids, 20:5ω3, 22:6ω3 and the ω3 fatty acids also correlated strongly with the wet weight of pike larvae. We demonstrated that several factors impact on pike larval growth.     

Habitat preferences of selected demersal fish species in the Bay of Biscay and Celtic Sea, North-East Atlantic

According to the Ideal Free Distribution theory, individual fish are distributed where environmental conditions are optimal, and the occupied area may vary with population abundance. Thus, observed distributions are a combination of habitat suitability and density-dependent effects. Data from an annual bottom trawl survey taking place in autumn were used to assess associations between the distributions of eight demersal fish species, separately for juveniles and adults, and habitat characteristics (depth, temperature and salinity) in the Bay of Biscay and Celtic Sea. Cumulative distribution functions were used to describe the general frequency distributions of environmental variables and their relationships with fish density. During the period 1992–2006, observed bottom temperatures fluctuated with no time trend (ΔT = 8°C in the first 80 m) and population abundances varied significantly. Juvenile hake, poor cod, blue whiting, adult red gurnard, adult megrim, and lesser-spotted dogfish were found to be significantly associated with specific depth ranges. Associations with bottom temperature and salinity were weaker. For some species, preferred environmental conditions changed over time, independently of variations in environmental conditions. In general, most species seemed to be able to cope with the experienced range of conditions. Habitat associations were not influenced by abundance variations. Fluctuating abundances had an impact on spatial occupation only for red gurnard adults, lesser-spotted dogfish and blue whiting juveniles, independent of absolute densities.     

Spatial distribution and feeding habits of Pacific cod (Gadus macrocephalus) larvae in Mutsu Bay, Japan

The spatial distributions and feeding habits of Pacific cod ( Gadus macrocephalus ) larvae, and the spatial distributions of copepod nauplii and copepodites, their main prey, were examined in Mutsu Bay from February to March during 1989–92. Yolk-sac larvae were caught at 30–45 m depth at the bay mouth. Larvae without yolk were collected at 8–45 m depth at the bay mouth and the inner part of the bay, and large larvae were chiefly found in the bay. This geographical pattern in larval size may have been because of transport to the inner part of Mutsu Bay by the Tsugaru Warm Current. The dominant taxa of copepod nauplii and copepodites in the diet and the environment changed each year. Larvae fed mainly on abundant taxa in the environment, suggesting that larvae are opportunistic feeders. Nauplii and copepodites were abundant in the bay, especially in 1992. Copepodites were slightly more abundant in the diet of cod larvae in 1992 than in 1991, but this difference was smaller than in the environment. In addition, larvae with empty digestive tracts were scarce in 1991 and 1992. Prey concentrations in the bay in 1991 and 1992 seem to have been high enough to sustain most Pacific cod larvae.     

Larval group differentiation in Atlantic cod (Gadus morhua) inside and outside the Gullmar Fjord

The spatial and temporal occurrence of pelagic fish stages and their biological variability may affect their dispersal and survival, and ultimately fish recruitment. We collected Atlantic cod larvae at one station inside and at one station outside the Gullmar Fjord, eastern Skagerrak, in order to investigate small-scale larval group differentiation. Rectangular midwater trawl hauls were taken every 6 h (during 24 h) from three separate depth intervals between the surface and 70 m depth. About 80% and 20% of all larvae occurred above the halocline at the Fjord station and the Coastal station, respectively. Hatching (at both stations) occurred from the 3rd week in February to the 1st week in May, indicating that cod larvae were present for at least 5 months (from late February to early August). The length and hatch date frequency distributions of larvae from the surface layer were unimodal inside the fjord but bimodal outside the fjord. Analyses of seven microsatellite DNA loci indicated that larvae collected inside the fjord (where local spawning occurs) were genetically distinct from larvae sampled on the outside (F_ST = 0.0026). The two age cohorts outside the fjord were not, however, genetically different, nor were larvae collected at different depths. We conclude that small-scale variability of vertical concentration and larval life history variability should have consequences for interpreting models of larval dispersal and survival, and subpopulation structure analyses.