Food and feeding habits of ribbonfish Trichiurus lepturus in coastal waters of south-western Taiwan

ABSTRACT:   The catch of ribbonfish Trichiurus lepturus in the coastal waters of south-western Taiwan has significantly declined in recent years. To examine the effects of exploitation on the feeding habits of ribbonfish, 1570 specimens were collected on a monthly basis during March 2002–March 2003 from the landings by trawlers operating in the coastal waters of south-western Taiwan. The size of the ribbonfish ranged from 83–298 mm preanal length (PL), with a peak at 201–250 mm PL. Although they fed on shrimps and squid, fishes including Benthosema pterotum , Bregmaceros lanceolatus and Encrasicholina heteroloba were their main food items . In particular, B. pterotum was the most important food all year except during summer. No evidence of cannibalism was found in this study. No differences between day and night were found in the feeding activity of T. lepturus . However, B. pterotum and Acetes intermedius were the most important prey in the daytime, whereas B. lanceolatus , B. pterotum and E. heteroloba were at night. Feeding activity and the number of food items increased with increasing size of ribbonfish. Their feeding intensity in February to June, the main spawning season, was significantly greater than in other months. Changes in the food and feeding habits of this species before and after the recent period of heavy exploitation are discussed in detail in this study.     

Seasonal movements of silver kob, Argyrosomus inodorus, (Griffiths and Heemstra) in Namibian waters

A seasonal migration pattern for silver kob, Argyrosomus inodorus (Griffiths & Heemstra) is elucidated based on tag-recapture data. Spawning adults start migrating southwards against the north-westerly surface currents at the beginning of the austral summer from the northern end of their distributional range to their spawning grounds, Sandwich and Meob Bays, at the southern end of their distributional range. It is suggested that after spawning larvae drift north with the current to the nursery areas, the West coast Recreational area (WCR). When juveniles reach the age of approximately 2 years they will gradually move north towards the adult feeding ground, the Skeleton Coast Park (SCP) waters. At the end of the spawning season when the surf-zone water temperature decreases to about 15 °C adult silver kob complete their spawning cycle by returning to the adult feeding ground, probably moving slightly offshore and with the current.     

福建中部近海鱼类生态类群的季节变化

为探究福建中部近海鱼类生态类群组成的季节变化,采用非线性多维标度(NMDS)和相似性检验(ANOSIM)方法,依据2009年冬季、2010年春季和夏季于福建中部近海3个航次的海洋综合调查资料,对该海域鱼类的种类组成和生态类群结构进行分析。结果显示,冬季出现鱼类40种,生态类群以暖水种为主,但暖温种比例为3个季节中最高(30%),且暖温种占该季鱼类总质量和总尾数比例分别为17.65%和16.96%。春季出现鱼类39种,生态类群以暖水种为主,分别占该季节鱼类总质量和总尾数的86.48%和94.52%。夏季出现鱼类61种,暖水种占绝对优势(56种),分别占该季鱼类总质量和总尾数的97.17%和99.35%。受浙闽沿岸流和台湾海峡暖流的交替影响,从冬季到夏季物种更替率逐渐升高,暖水种种类数和数量密度不断上升,并伴随着河口种消失、外海种出现。此现象与冷、暖水团交替影响这一海域时,鱼类进行相应的产卵、索饵及越冬洄游等有关。研究表明,福建中部近海鱼类生态类群和种类组成的季节变化可能由水团不断变化所导致。     

Variations in spawning ground area and egg density of the Japanese sardine in Pacific coastal and oceanic waters

The spawning ground of the Japanese sardine, Sardinops melanostictus (Schlegel), was distributed over the oceanic waters as well as the coastal waters along the Pacific coasts of western and eastern Japan during 1978–1992. The area of the spawning ground in the coastal waters on the continental shelf has ranged from 95 000 km² in 1992 to 143 000 km² in 1988, constituting 44–77% of the total area of the spawning ground. The area of the coastal spawning ground was relatively constant in spite of the large fluctuations in egg abundance, i.e. size of the spawning population, from 88 trillion (1987) to 668 trillion (1989) in the waters. Spawning adults seemed to extend over the coastal waters irrespective of the size of the spawning population. In contrast to the coastal waters, the spawning area in the oceanic waters offshore of the continental shelf increased from 31 000 km² in 1978 to 183 000 km² in 1988 and then shrank to 83 000 km² in 1992, as a function of the spawning population size. The egg distribution density in the coastal waters stayed less than 6000 m⁻² mo⁻¹, but it reached as high as 27 400 m⁻² mo⁻¹ in the expanded spawning ground in the oceanic waters. The oceanic waters seemed to function as a reserve spawning ground for the sardine in years of extremely high spawning population.     

Using coupled fish behavior–hydrodynamic model to investigate spawning migration of Japanese anchovy,Engraulis japonicus,from the East China Sea to Taiwan

Adult Japanese anchovies (Engraulis japonicus) migrate from the East China Sea to the coastal region of Taiwan to spawn around late winter and early spring and, later, their larvae constitute important fisheries in Taiwan. However, their migration route and its mechanism remain unclear. To investigate their spawning migration, we used a coupled fish behavior–hydrodynamic modeling approach. The physical field is simulated by the Pacific Ocean adaptation of the TaIwan Multi‐scale Community Ocean Model (TIMCOM) and the fish migration by Lagrangian tracer tracking with the aid of approximation of fish swimming behavior. We investigated three fish behavioral scenarios: (i) passive tracking of the current, (ii) swimming along with the current, and (iii) swimming along with the current and then changing to swimming toward the optimal spawning temperature. The comparison with and without Changjiang discharge is used to investigate the impacts of discharge reduction due to the Three Gorges Dam. Our results suggest that spawning migration of Japanese anchovy from the East China Sea to Taiwan may be aided by the China Coastal Current and that adult anchovies cannot reach the spawning site by passive advection alone. Thus, the swimming behavior of anchovies is crucial during the spawning migration, as it provides extra velocity and the orientation to the favorable spawning grounds. In addition, the adult anchovy is unlikely to reach the coastal area of Taiwan without Changjiang discharge. Our findings indicate that a coupled fish behavior–hydrodynamic model can help understand the influences of physical environment on the migration of Japanese anchovies.     

Feeding habits of Baird's beaked whale Berardius bairdii, in the western North Pacific and Sea of Okhotsk off Japan

ABSTRACT:   We examined the stomach contents of 26 Baird's beaked whales caught off the coast of Japan by small-type coastal whalers. The main prey for these whales was rat-tails and hakes in the western North Pacific. Pollock and squids were also important food in the whales collected from the southern Sea of Okhotsk. The prey species found in the stomachs of the whales were almost identical to those caught in bottom-trawl nets at depths greater than about 1000 m in the western North Pacific, which suggests that the Baird's beaked whale forages for prey at depths of about 1000 m or more. Baird's beaked whales in the western North Pacific migrate to waters of 1000–3000 m in depth, where demersal fish are abundant. This implies that Baird's beaked whales migrate to waters where demersal fish, especially rat-tails and hakes, are abundant. Although there is limited information on the feeding habits of ziphiid whales, they are generally thought to prefer squid. The present data suggest that demersal fish are also important prey for ziphiid whales.     

中国主要海洋底层鱼类生物学研究的回顾与展望

回顾了中国海洋主要底层经济鱼类资源生物学的研究历史和科研成果,并重点叙述了带鱼、小黄鱼、大黄鱼和绿鳍马面鲀等重要经济鱼类资源生物学研究概况.概述的内容包括地理种群及其产卵群体的鉴别和划分、生活史型的演变、种群和群体结构、种群数量变动、年龄组成和生长特性、摄食习性、性成熟周期、性腺成熟指数(GSI)、产卵群体生殖力、产卵场、索饵场、越冬场及洄游路线、资源量和渔获量、各种作业渔船的调整及其捕捞力量的限制措施等,并展望了中国海洋底层经济鱼类资源生物学研究的前景.     

Migration and spawning behavior of the greater amberjack Seriola dumerili in eastern Taiwan

Greater amberjack (Seriola dumerili) is an important fishery resource with a circumglobal distribution from tropical to temperate waters. Here, we investigated the spawning migration and habitat utilization of S. dumerili in the East China Sea (ECS). Archival tags were attached to 22 adult fish to examine their horizontal and vertical movements and estimate the spawning ground. S. dumerili were captured and released in the coastal waters of eastern Taiwan on November of 2016 and 2017. Information from seven pop-up satellite archival tags and seven depth–temperature recorders was recovered. Almost all of the fish stayed in the Taiwanese exclusive economic zone. Most individuals moved from released site to the southern edge of the ECS and showed behavior associated with the topographic features in winter (November to December). These phenomena may be related to foraging and be driven by oceanographic features such as the seasonal monsoon and the Kuroshio. The fish then migrated to the south offshore area of Taiwan in January and February. During their southward migration, the fish experienced a slowly elevated water temperature regime (SETR), which is one of the environmental factors that induce final oocyte maturation. In the spawning season (February to April), tagged females exhibited continuous diel vertical movements (DVMs) after experiencing the SETR. These continuous DVMs were observed over a wide geographic range from north to south in the Kuroshio off eastern Taiwan. Our study demonstrated that the putative spawning ground of S. dumerili must extend further in a north–south direction than predicted in a previous study.     

Food and feeding habit of taiwan mauxia shrimp <Emphasis Type="Italic">Acetes intermedius</Emphasis> in the coastal waters of Southwestern Taiwan

The stomach contents and feeding habits of the Taiwan mauxia shrimp Acetes intermedius were examined based on 420 specimens collected in the costal waters of south-western Taiwan. Two 24-h periodic samplings of specimens were completed to describe the diel feeding periodicity of this species. Phytoplankton was the main food for the Taiwan mauxia shrimp, and the dinoflagellates was the most important food. They also fed on zooplankton and amorphous materials. Their diet changed with the seasons. The feeding activity of this species mainly occurred at night. The results obtained in this study supported the hypothesis that A. intermedius performs a nocturnal vertical migration to avoid predators and to allow for safe feeding.     

The influence of seasonal environmental changes on ontogenetic migrations of the squid Loligo gahi on the Falkland shelf

The Patagonian longfin squid Loligo gahi undertakes horizontal ontogenetic migrations on the Falkland shelf: juveniles move from spawning grounds located in shallow, inshore waters (20–50 m depths) to feeding grounds near the shelf edge (200–350 m depths). Immature squid feed and grow in these offshore feeding grounds and, upon maturation, migrate back to inshore waters to spawn. The possible influence of environmental factors on L. gahi migrations was investigated using data from oceanographic transects, crossing the region of known L. gahi occurrence. They were made from the inshore waters of East Falkland eastwards to depths of 1250 m on a monthly basis from 1999 to 2001. Four main water types were found in the region: Shelf, Sub‐Antarctic Superficial and Antarctic Intermediate water masses, and Transient Zone waters. The inshore spawning grounds occur in the Shelf Water mass, whereas the feeding squid (medium‐sized immature and maturing individuals) were associated with the Transient Zone. The 5.5°C isotherm appeared to mark the limit of squid distribution into deeper waters in all seasons. Seasonal changes in water mass characteristics and location were found to be important for seasonal changes in L. gahi migrations on the Falkland shelf.     

Effects of lunar phase and habitat depth on vertical migrationpatterns of the sergestid shrimp Acetes intermedius

ABSTRACT:   The effects of lunar phase and habitat depth on the verticalmigration patterns of the sergestid shrimp Acetes intermedius wereexamined based on seven field observations in coastal waters offsouth-western Taiwan. The results indicate that the pattern of nocturnalvertical movement of A. intermedius depends on the lunarphase. The shrimp evaded moonlight during the ascending period andthen the moon was used as a trigger for resuming an ascent towardsthe sea surface or descending towards the 10 m water layer.During the descending period, A. intermedius moved rapidlyto the bottom or to a middle water depth at 50–80 mbefore sunrise. However, A. intermedius in waters of deepKaoping Canyon can also perform a slow descending migration thatcoincides with photosynthetically active radiation of 4 µmol/sper m². Because the density of A. intermedius onthe surface layer is affected by moonlight, the lunar phase is oneof the factors affecting the catch rate of large-skimming nets duringthe night in waters off south-western Taiwan.     

山东半岛南部近岸海域蟹类群落结构特征

根据使用单船底拖网进行2014年8月和10月、2015年2月和5月4个航次的调查数据,对山东半岛南部近岸海域蟹类种类组成、时空分布、优势种、物种多样性等群落结构特征进行了研究。结果显示,4次调查共捕获蟹类15种,隶属于7科12属,其中三疣梭子蟹(Portunus trituberculatus)、日本蟳(Charybdis japonica)是主要经济种类,其余多为小型饵料型蟹类;双斑蟳(C.bimaculata)在4个季节中皆为优势种,三疣梭子蟹在8月和10月航次为优势种,优势种季节更替明显;生物量季节变化明显,春季时较低,在夏季达到峰值,夏季到冬季呈降低趋势;蟹类群落物种多样性指数(H′)变化范围为0.32~0.53,均匀度指数(J′)变化范围为0.23~0.37,丰富度指数(D)变化范围为0.32~0.55,其中物种多样性指数与丰富度指数季节变化明显,均匀度指数季节变化不明显;多元统计分析结果表明,山东半岛南部近岸海域4季节蟹类群落结构均可以划分为西南部海域组、东北部远岸海域组和西北部近岸海域组3个组群,季节间组群站位组成变化明显,群落结构不稳定。研究表明:1)山东半岛南部近岸海域蟹类以小型饵料型蟹类为主,蟹类多样性水平较低,优势种更替明显,蟹类群落不稳定;2)山东半岛南部近岸海域蟹类群落划分较为明显,特征种主要为双斑蟳、泥脚隆背蟹(Carcinoplax vestita)等小型饵料型蟹类。     

东、黄渤海带鱼的洄游路线

为了研究带鱼的洄游路线,根据我国10余个主要渔业公司1971、1972、1981和1982年带鱼捕捞统计资料,先绘制带鱼鱼群移动影像图,据此进一步研究东、黄渤海近海带鱼的洄游路线图。结果显示,带鱼越冬场、产卵场和索饵场范围广阔,在空间上具有一定的重叠性。带鱼还有分批越冬、产卵和索饵洄游的特性,不同群体越冬、产卵和索饵洄游在时间上也有一定的重叠性。北方带鱼群体的越冬场主要在32°00'～36°00'N,124°00'～126°00'E黄海暖流水域。3—7月北上进入海州湾、乳山湾、海洋岛和渤海各湾产卵场;8—9月在产卵场外围宽阔水域索饵;9—11月游出渤海,绕过成山头南下,沿禁渔线外侧,沿途分别汇合海州湾、乳山湾及海洋岛的越冬鱼群,到了34°00'N后折向东南,分批于12月到达越冬场。南方带鱼群体越冬场主要位于浙江中南部禁渔线外侧,其次是济州岛西南海域。每年3—4月起,南部越冬的带鱼鱼群大致以每2个月1个纬度的速度向东北方向移动;5—7月,产卵洄游的鱼群到达舟山渔场和长江口渔场产卵;7—8月,产卵后的索饵群体北上黄海南部大沙渔场索饵;9月,索饵群体前锋到达35°00'N禁渔线外侧。10月以后,随着冷空气南下,南部群体带鱼向南越冬洄游,并且在10月回到长江口海域。其中小部分群体游向外海越冬场,大部分群体继续南下回到东海中南部近海的越冬场。台湾暖流和黄海暖流的进退和消长是影响带鱼越冬洄游路线空间和时间变化的主要环境因素。     

黄海南部和东海浮游动物分布与鲐鯵渔场关系

黄海南部和东海的日本鲐鱼和蓝圆鲹以浮游动物为主食,并兼食鯷鱼等小型鱼类。因此浮游动物的分布及其季节变化同鲐、鲹渔场的关系密切。本文报导了1972—1975年间,对黄海南部和东海浮游生物组成和数量分布的调查结果,并据此对鲐、鲹渔场的位置、渔期、渔获量以及洄游路线等进行了分析研究。不同季节,鲐鲹鱼类的产卵群、索饵群和越冬群形成的渔场位置及其变迁,都和浮动动物的分布、数量变化有密切的关系。     

Temperature conditions in the Argentine chub mackerel (Scomber japonicus) fishing ground: implications for fishery management

We describe the seasonal migrations of Argentine chub mackerel ( Scomber japonicus ) into the fishing ground in relation to sea surface temperature conditions and analyse the temperature evolution during the fishing season on the basis of 1955–97 time-series. The upper temperature limit for the presence of schools was around 19°C. At higher values, most schools leave coastal waters (< 50 m) for the shelf. An inverse relationship was observed between catches per unit of effort (CPUE) of the inshore fishery and sea surface temperature. The highest standardized CPUE values corresponded to temperatures lower than 19°C. Above this temperature, the probability of obtaining a standardized CPUE higher than 1 was extremely low, and the standard deviations were minimal. The economic benefit from catches was also analysed through the different months of the fishing season. It was found that the mean benefit corresponding to temperatures lower than 19°C exceeded approximately 15 times that obtained at higher temperatures. A simple fishing strategy was proposed to the commercial fleet in order to improve the economic benefit of the catches. The migratory pattern followed by mackerel during the spawning period was also analysed in relationship to other environmental factors like food availability. Zooplankton composition, size structure and abundance in coastal and shelf waters are described, and their implications for feeding ecology of larvae and adults of the species are discussed.     

Staged spawning migration in Icelandic capelin (Mallotus villosus): effects of temperature,stock size and maturity

Capelin (Mallotus villosus) is the largest commercial fish stock in Icelandic waters and also an important forage fish. Every winter pre‐spawning capelin migrate 500–1000 km from their offshore (>200 m bottom depth) northern feeding areas (67–71°N) to inshore (<200 m bottom depth) southern spawning areas (63–65°N). The major migration route is east of Iceland. The route consists of both offshore and inshore phases. The migration begins offshore as capelin skirt the shelf edge north of 65°N, then abruptly veer inshore between latitudes 64° and 65°N. Hydro‐acoustic data from 1992–2007 demonstrated that the timing of the offshore phase migration varied by as much as 1 month, from 22 December to 21 January. A combination of larger spawning stock and colder feeding ground temperatures (August–December) resulted in earlier offshore migration. The timing of the inshore migration phase was not dependent on the offshore migration timing, and never began prior to the first week of February. Many cohorts arrived at latitudes 64–65°N in early January but staged offshore at latitudes 63.8–65.8°N until early February. The longest observed delay in the staging area was 5 weeks. Timing of the inshore migration was controlled by gonad maturity, with migration beginning when roe content attained 12–14%. Staging limited the time capelin spent on the continental shelf before spawning to 3 weeks. We suggest that offshore staging evolved to minimize temporal overlap with predatory gadoids, especially Atlantic cod (Gadus morhua).     

Movement patterns of armado, Pterodoras granulosus, in the Paraná River Basin

Abstract –  We studied the migratory behaviour of armado, Pterodoras granulosus , in the Paraná River Basin of Brazil, Paraguay and Argentina, during 1997–2005. This species invaded the Upper Paraná River after upstream dispersal was facilitated when Itaipu Reservoir inundated a natural barrier. Fish were tagged ( N  = 8051) in the mainstems of the Yacyreta and Itaipu reservoirs, bays of major tributaries, the Paraná River floodplain above Itaipu Reservoir, and below dams. In all, 420 fish were recaptured of which 61% moved away from the release area. Fish moved a maximum of 215 km (mean 42), and at a maximum rate of 9.4 km·day⁻¹ (mean 0.6). Of the 256 armados that moved away from the release site, 145 moved upstream towards unimpounded stretches of the Paraná River and 111 moved downstream into the reservoir and bays of its tributaries (maximum 150 km). Based on the observed migratory movements, we suspect that most of the reproductive output originates in tributaries to the reservoirs. The ability of this species to expand its range presents a conundrum by pitting fishery management interests against conservation needs. Maintenance of the important armado fisheries depends on the ability of the species to migrate freely to use spawning and nursery areas in reservoir tributaries and floodplains. However, its ability to migrate long distances can allow this non-native species the opportunity to invade most of the Upper Paraná River.     

黄海北部辽宁近岸海域鳀产卵场分布特征及其影响因素

为掌握黄海北部辽宁近岸海域鳀(Engraulis japonicus)产卵场的分布特征及其关键环境因子,基于2021年4—12月开展的产卵场综合调查获取的鳀样品及其鱼卵密度数据,运用Garrison重心分布法阐释鳀产卵洄游分布特征及其主产卵期;通过基于Tweedie分布的广义可加模型(generalized additive model, GAM)的构建,分析主产卵期内鳀卵密度与同步获取的海水表层温度(SST)、海水表层盐度(SSS)、海水表层叶绿素浓度(Chla)、浮游动物丰度(Fd)、浮游植物丰度(Fz)和深度(Depth)等6个环境因子,以及时间(月份,Month)和空间(经纬度、Lon和Lat)因子之间关系,并识别主控因子。结果显示,海域内鳀产卵期较长,由4月持续至11月,5—8月为主产卵期,其中,5—6月为产卵盛期。鳀产卵场规模和位置时空变化明显,时空因子与鳀卵密度分布呈密切非线性相关(累积偏差解释率为48.1%),(SST, SSS) (18.7%)和Depth (5%)次之。鳀产卵期适温范围较广,产卵场分布表现出高温高盐(低温低盐)增效作用和高温低盐限制作用。产卵初期(4月),鳀产卵场规模和鱼卵密度均较低,产卵重心位于海洋岛东南侧深水区;盛期(5月底—6月初)在SST主导下,鳀产卵场规模和鱼卵密度均至年内最高值,核心产卵场位于石城岛–庄河河口一带海域;此后,随着辽南沿岸水系盐度的下降,高温低盐的抑制作用使SSS因素主导产卵鱼群避开沿岸海域,鳀产卵场迁移至外海深水区,7月后位于30~50 m等深线之间;9—10月鳀繁殖活动基本结束,10月鳀卵仅零星分布于调查海域,直至12月未有鳀卵采获。研究可为黄海北部辽宁近岸海域鳀产卵场研究及鳀资源合理开发利用提供参考依据。     

海州湾及邻近海域春夏季典型断面鱼类浮游生物群落的结构特征

根据2015年5―7月在海州湾及邻近海域存在空间异质性的南北两个典型断面进行的鱼卵、仔稚鱼水平拖网调查数据,采用多元统计分析等方法研究了该海域春、夏季鱼类浮游生物群落的空间变化。结果表明,本次调查共获得鱼卵33587粒,仔稚鱼713尾。出现鱼卵25种(未定种1种),隶属于14科25属,仔稚鱼13种(未定种1种),隶属于13科13属。鱼卵优势种主要是鳀(Engraulis japonicus)、多鳞鱚(Sillago sihama)、(魚銜)属(Callionymus spp.)、皮氏叫姑鱼(Johnius belengerii)、江口小公鱼(Stolephorus commersonni)和短吻红舌鳎(Cynoglossus joyneri);仔稚鱼优势种主要是(魚銜)属和斑鰶(Konosirus punctatus)。鱼类浮游生物种类组成年代际变化明显,目前以生命周期短、个体小、资源更新节律快的小型鱼种为主;研究表明,鱼类浮游生物的优势种在不同月份和断面之间存在一定变化,5、6月南北两断面优势种组成不同,7月开始出现共同优势种。从鱼类浮游生物的空间分布来看,近岸海域的丰度较高,5、6月鱼类浮游生物的平均丰度均为北面断面1高于南面断面2,7月反之。鱼类浮游生物群落在两个典型断面随月份呈现出不同特征,水深、温度和盐等海洋环境因子综合影响着春、夏季海州湾及邻近海域鱼类浮游生物群落结构。     

Genetic identification of <Emphasis Type="Italic">Conger myriaster</Emphasis> leptocephali in East China Sea

ABSTRACT:   A subsample of Conger leptocephali collected in the East China Sea (ECS) was genetically analyzed and most were found to be the larvae of Conger myriaster , the most commercially important marine eel species in East Asia. However, these leptocephali (22.3–74.0 mm total length [TL]) did not have a complete row of lateral pigmentation, like the leptocephali of this species are commonly known to have when they are collected over the continental shelf or in coastal waters as they recruit. These leptocephali were in the western edge of the Kuroshio Current and the mixing zone over the shelf in the northern part of the ECS, and two smaller leptocephali (22.3, 46.5 mm TL) were collected to the south of the Ryukyu Islands. This evidence of an ontogenetic change in the presence of lateral pigmentation of C. myriaster indicates that previous efforts to determine the spawning area and recruitment patterns based on only morphological examination of Conger leptocephali in the region must be reconsidered. New research efforts based on genetic identification methods are needed to understand the spawning ecology and recruitment of this important fishery species.