Distribución,Abundancia y Reproducción de Harengula jaguana Goode y Bean, 1879, en la Plataforma Continental del Sur del Golfo de México (Pisces: Clupeidae)1

Harengula jaguana is a dominant species in the southern Gulf of Mexico. It is a demersal, estuarine-dependent species, distributed throughout the Campeche Sound area (12-54 m). It is found in areas influenced by coastal discharges. The size at first maturity of females is 117 mm total length. Reproduction occurs from February to October in depths 18-36 m. The juveniles are found on the shelf (<20 m) and inside the Terminos Lagoon. Recruitment is in two distinct periods, March–June and August–November, when adults and juveniles migrate to the outer shelf. Greatest abundance is observed in depths of 12-36 m. The biology and ecology of H. jaguana was analyzed in the Campeche Sound to better understand the structure and function of the demersal fish communities. It is a very important species in the trophic dynamics of the ecosystem because it transports matter and energy. A model of the biological pattern for this species in the area is proposed.     

Mapping of the Biological Resources of the Continental Shelf

Distribution patterns of the penaeid shrimp and demersal fishspecies are discussed based upon collections totaling in excessof 330,000 shrimp and 2,245,000 fishes. Depth related zonationreveals nearshore, mid-shelf, outer shelf, and trans-shelf assemblages.Estuary related species are particularly prominent on the northwesternGulf shelf, while rock and reef related species are most importantin the fauna of the eastern Gulf shelf. Recognizable elementsin the shelf fauna also include species of tropical affinity;open ocean and upper slope species; inhabitants of seagrassbeds, mangrove swamps, and carbonate rubble and shell hash;burrowers in soft bottoms; and inhabitants of the upper watercolumn. The eastern Gulf shelf is inhabited by twice as manyfish species and eight times as many unique species as the northwesternshelf, reflecting the great diversity of habitat types in theeastern Gulf. A few key species numerically dominate the ichthyofaunaof the northwestern shelf, but dominance is spread through manyspecies in the east. Seasonal shifts in species density primarilyreflect inshore/offshore seasonal migrations of estuary relatedspecies, but seasonal inshore/offshore density shifts are alsoobserved among the true shelf residents. Trophically the shelfsystems are supported by precipitated plankton and organic detritusderived from rivers, bays and estuaries, seagrass beds, andmangrove swamps, although attached algae are also importantproducers in the east. Mollusks, polychaetes, and small crustaceanswhich feed upon this material, in turn, support the demersalfish communities whose species are generally short-lived. Largerlonglived predators are mostly seasonal migrants which appearin the northern Gulf during the warmer months. Bottom-feedinggeneralists are prominent in the northwest, while specialistsare in great evidence in the east. These distributional studieslay the foundation for understanding the shelf ecological systems,and they also provide a basis for informed management decisions.     

Feeding habits and trophic morphology of inshore lizardfish (Synodus foetens) on the central continental shelf off Veracruz, Gulf of Mexico

The inshore lizardfish, Synodus foetens, is one of the most common coastal demersal predators on the continental shelf of the Gulf of Mexico (GOM), but the biology and feeding ecology of this species is virtually unknown. Between November 2001 and January 2003 (10 collections), 603 individuals of S. foetens ranging from 112 to 420 mm standard length (SL) and 13 to 630 g (wet weight) were collected from the continental shelf of Alvarado, Veracruz, Mexico. About 60% of the individuals had empty stomachs with the stomach fullness of the remaining individuals being distributed as follows: 5% full (24.8%), 50–75% full (13.5%), and completely full (1.7%). The mean (± SD) wet weight of stomach contents was 12.1 ± 10.8 g during the rainy season, and 19.0 ± 13.0 g during the nortes season. Seventeen prey items were identified, with the majority thereof being fish. The most important prey items were Upeneus parvus, Loligo pealei, Engyophrys senta, Trachurus lathami, and Anchoa hepsetus. Seasonal changes in the diet were observed, with U. parvus and L. pealei being the most important prey during the nortes season, whereas E. senta and L. pealei were the main items during the rainy season. Prey size selection was evident among size classes of S. foetens, although no trophic overlap was observed among size classes (C_ik ≤ 0.004). High trophic level values were determined for all size classes by season (rainy season = 4.67, nortes season = 4.84), and indicated this species belongs to the piscivorous trophic guild that preys upon both demersal and pelagic species.     

Demersal fish diversity of the isolated Rockall plateau compared with the adjacent west coast shelf of Scotland

This study compares the diversity of the demersal fish assemblage of an isolated shelf sea, the Rockall plateau, with that of the nearest adjacent continental shelf sea ecosystem, the west coast of Scotland. Bottom trawl surveys were carried out between 1986 and 2008 on the Rockall plateau and the adjacent shelf sea to the west of Scotland. All demersal fish were identified and counted. Analyses of species richness and abundance were undertaken. The fish assemblage of the Rockall plateau was less diverse and the proportional representation of species was markedly different. A number of species common at Rockall were rare on the west coast shelf and, in general, there were fewer common and temporally stable species and more rare and ephemeral species at Rockall. Some species absent from Rockall have life‐history stages associated with inshore habitat. The Rockall plateau fish assemblage can be described as an impoverished subset of the north‐west European shelf sea fish assemblage. It is likely that there are constraints on diversity imposed by the relatively small area of the Rockall plateau and its degree of isolation by depth, distance and ocean currents. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 104 , 138–147.     

Distribution of fishes on the Cretan shelf

Information on the abundance of demersal fishes on the shelf of Crete has been collected through a 3-year bottom trawl survey carried out at fixed sampling stations. Cluster analysis identified three major station-groups delimited by the nature of the substrate. Two of the identified substrate zones were situated on the continental shelf while the beginning of the third zone coincided with the start of the continental slope. Discriminant analysis applied to the abiotic variables defined that depth was the most important variable in discriminating between the identified groups. Discriminant analysis also identified that the most important species in discriminating among station-groups were Capros aper (Linnaeus, 1758), Gadicuh argenieus argenteus Guichenot, 1850, Merluccius merluccius (Linnaeus, 1758), Mullus surmuletus Linnaeus, 1758 and Spicara flexuosa Rafinesque, 18 10. Association analysis revealed few species pairs having significant associations which in most cases seem to be related to the reproductive migration of these species. The results demonstrate that there is a pronounced change with the substrate and by extension with depth in the ichthyofaunal composition of the shelf of Crete. It has also been suggested that there may be a particular relationship between the fish communities of the two zones of the continental shelf.     

Stomatopods (Crustacea: Hoplocarida) from the Gulf of Tehuantepec, Mexico

A total of 1,173 specimens of Stomatopoda were captured in 27 localities at different depths (20 to 73 m) during three oceanographic cruises in the Mexican Pacific along the continental shelf of the states of Oaxaca and Chiapas. Seven species were identified of the families Eurysquillidae, Lysiosquillidae and Squillidae. Squilla hancocki and Squilla parva were the most abundant species and the most frequently found together. The relationships between total length and carapace length were obtained for these species, which show that males of S. hancocki have a longer carapace length than females having the same total length, whereas for S. parva the opposite occurs. Larger sizes than previously reported were obtained for Lysiosquilla panamica and Squilla mantoidea. Squilla bigelowi was recorded for the first time in the Gulf of Tehuantepec. All the species were found in the intermediate platform (25-60 m); E. veleronis, S. hancocki and S. parva extended their distributions to the external platform (60-120 m), and S. hancocki and S. parva reached the circalittoral zone (10-25 m).     

Reproduction of the spiny puffer, Diodon holocanthus (Pisces: Diodontidae) in the continental shelf of Mexican Central Pacific

Diodon holocanthus is an important economic and ecological species of the demersal fish community, caught as bycatch from local shrimp fishery. The reproductive biology of this long-spine porcupinefish has not yet been described, and reproductive season, the sex ratio, length distribution, length at first gonad maturity, and the gonad macro and microscopic features are described. A total of 400 organisms, ranging from 5.0 to 40.3 cm (average 18.4 cm) total length, were caught from the continental shelf of the Central Mexican Pacific, from December 1995 and December 1998. Sex ratio was 1:0.86 females to males (n = 253). The length at which 50% of the individuals showed maturing gonads was 19.7 cm for females and 20.1 cm for males. Length of the smallest organism with ripe gonads was 12.2 cm for females and 13 cm for males. Four gonadal maturation stages were found in both sexes, and five oocyte development phases were identified. The oocyte development pattern is of asynchronous type, which means the species can reproduce several times a year. Testicle development is lobular type, as in most teleost fishes. Monthly mean values of the gonad-somatic index suggest the reproduction activity peaks in June, and September-December.     

Habitat specialization in tropical continental shelf demersal fish assemblages

The implications of shallow water impacts such as fishing and climate change on fish assemblages are generally considered in isolation from the distribution and abundance of these fish assemblages in adjacent deeper waters. We investigate the abundance and length of demersal fish assemblages across a section of tropical continental shelf at Ningaloo Reef, Western Australia, to identify fish and fish habitat relationships across steep gradients in depth and in different benthic habitat types. The assemblage composition of demersal fish were assessed from baited remote underwater stereo-video samples (n = 304) collected from 16 depth and habitat combinations. Samples were collected across a depth range poorly represented in the literature from the fringing reef lagoon (1-10 m depth), down the fore reef slope to the reef base (10-30 m depth) then across the adjacent continental shelf (30-110 m depth). Multivariate analyses showed that there were distinctive fish assemblages and different sized fish were associated with each habitat/depth category. Species richness, MaxN and diversity declined with depth, while average length and trophic level increased. The assemblage structure, diversity, size and trophic structure of demersal fishes changes from shallow inshore habitats to deeper water habitats. More habitat specialists (unique species per habitat/depth category) were associated with the reef slope and reef base than other habitats, but offshore sponge-dominated habitats and inshore coral-dominated reef also supported unique species. This suggests that marine protected areas in shallow coral-dominated reef habitats may not adequately protect those species whose depth distribution extends beyond shallow habitats, or other significant elements of demersal fish biodiversity. The ontogenetic habitat partitioning which is characteristic of many species, suggests that to maintain entire species life histories it is necessary to protect corridors of connected habitats through which fish can migrate.     

Decadal Changes in Zooplankton of the Northeast U.S. Continental Shelf

The abundance of the subarctic copepod, Calanus finmarchicus, and temperate, shelf copepod, Centropages typicus, was estimated from samples collected bi-monthly over the Northeast U.S. continental shelf (NEUS) from 1977–2010. Latitudinal variation in long term trends and seasonal patterns for the two copepod species were examined for four sub-regions: the Gulf of Maine (GOM), Georges Bank (GB), Southern New England (SNE), and Mid-Atlantic Bight (MAB). Results suggested that there was significant difference in long term variation between northern region (GOM and GB), and the MAB for both species. C. finmarchicus generally peaked in May – June throughout the entire study region and Cen. typicus had a more complex seasonal pattern. Time series analysis revealed that the peak time for Cen. typicus switched from November – December to January - March after 1985 in the MAB. The long term abundance of C. finmarchicus showed more fluctuation in the MAB than the GOM and GB, whereas the long term abundance of Cen. typicus was more variable in the GB than other sub-regions. Alongshore transport was significantly correlated with the abundance of C. finmarchicus, i.e., more water from north, higher abundance for C. finmarchicus. The abundance of Cen. typicus showed positive relationship with the Gulf Stream north wall index (GSNWI) in the GOM and GB, but the GSNWI only explained 12–15% of variation in Cen. typicus abundance. In general, the alongshore current was negatively correlated with the GSNWI, suggesting that Cen. typicus is more abundant when advection from the north is less. However, the relationship between Cen. typicus and alongshore transport was not significant. The present study highlights the importance of spatial scales in the study of marine populations: observed long term changes in the northern region were different from the south for both species.     

North Atlantic demersal deep‐water fish distribution and biology: present knowledge and challenges for the future

This paper summarizes knowledge and knowledge gaps on benthic and benthopelagic deep‐water fishes of the North Atlantic Ocean, i.e. species inhabiting deep continental shelf areas, continental and island slopes, seamounts and the Mid‐Atlantic Ridge. While several studies demonstrate that distribution patterns are species specific, several also show that assemblages of species can be defined and such assemblages are associated with circulatory features and water mass distributions. In many subareas, sampling has, however, been scattered, restricted to shallow areas or soft substrata, and results from different studies tend to be difficult to compare quantitatively because of sampler differences. Particularly, few studies have been conducted on isolated deep oceanic seamounts and in Arctic deep‐water areas. Time series of data are very few and most series are short. Recent studies of population structure of widely distributed demersal species show less than expected present connectivity and considerable spatial genetic heterogeneity and complexity for some species. In other species, genetic homogeneity across wide ranges was discovered. Mechanisms underlying the observed patterns have been proposed, but to test emerging hypotheses more species should be investigated across their entire distribution ranges. Studies of population biology reveal greater diversity in life‐history strategies than often assumed, even between co‐occurring species of the same family. Some slope and ridge‐associated species are rather short‐lived, others very long‐lived, and growth patterns also show considerable variation. Recent comparative studies suggest variation in life‐history strategies along a continuum correlated with depth, ranging from shelf waters to the deep sea where comparatively more species have extended lifetimes, and slow rates of growth and reproduction. Reproductive biology remains too poorly known for most deep‐water species, and temporal variation in recruitment has only been studied for few deep‐water species. A time series of roundnose grenadier Coryphaenoides rupestris recruitment spanning three decades of fisheries‐independent data suggests that abundant year classes occur rarely and may influence size structure and abundance even for this long‐lived species.     

Distribution,abundance and biology of polar cod, <Emphasis Type="Italic">Boreogadus saida</Emphasis>, in Iceland–East Greenland waters

Recent warming has caused a northern extension in the distribution of many southern fish species in Icelandic waters. Polar cod (Boreogadus saida) around Iceland are near the southern limit of their distribution, but are poorly studied in the area. Therefore, material sampled during demersal fish surveys in March 1985–2013 and in pelagic 0-group surveys in Iceland–East Greenland waters in August–September 1974–2003 was used to investigate their distribution, abundance and biology. Demersal polar cod were most often caught on the outer shelf to the north-west and north of Iceland, but during years of widest distribution and highest abundance, they were caught farther to the east on the northern shelf. Pelagic 0-group polar cod were only caught sporadically and mainly confined to the waters off the north-west shelf of Iceland and the East Greenland shelf (southern Denmark Strait). In demersal hauls, the number of stations with polar cod decreased with increasing bottom temperature and polar cod were most widely distributed in the years 1989, 1994 and 1995. Highest numbers of demersal polar cod per haul were caught at temperatures of ?0.5 to 2.5 °C and at 200–450 m depth. The length of demersal polar cod ranged from 5 to 32 cm, while the fish caught in the pelagic trawl ranged from 2.2 to 19 cm. The polar cod in the subarctic waters north of Iceland most likely originate from the waters off East Greenland and further warming and decline in sea ice may eventually lead to the disappearance of polar cod from Icelandic waters.     

Length–weight relationship of thirteen demersal fishes from the tropical Brazilian continental shelf

This study provides the length‐weight relationship (LWR) for 13 demersal fish species belonging to 11 families and 8 orders. Data were collected in the northeast Brazilian continental shelf during two scientific surveys (2015 and 2017) using a bottom trawl net (side length of body mesh: 40 mm, side length of cod‐end mesh: 25 mm) at 35 stations between 15 and 60 m of depth. We provide novel LWRs for four species and expand the size range of 9 relationships previously established.     

Distributional ecology of milkfish,Chanos chanos,larvae in the Great Barrier Reef and Coral Sea near Lizard Island,Australia

Synopsis Plankton hauls captured 682 milkfish larvae (2.1–12.3 mm) in the Great Barrier Reef Lagoon and Coral Sea during 1979–1986. Larvae were present from November to March, and absent in April, July and October. We analyzed concentration, abundance and size-frequency data and concluded that spawning took place in the Coral Sea or at the outer edge of the continental shelf, apparently following an adult spawning migration of at least 50 km. Larvae then moved inshore to at least our most inshore routine sampling site near midshelf. Some larvae may have remained for a period in the lee of reefs along the shelf edge. Larvae apparently occupied the upper few metres of the water column, thereby becoming susceptible to shoreward movement in the wind-driven surface layer. Movement from spawning sites to midshelf probably required active maintenance of vertical position by larvae which enabled passive movement with favourable currents, and perhaps horizontal swimming. By the time larvae reach midshelf, continued inshore movement by horizontal swimming alone is possible.     

Community structure of deep-sea demersal fish in the North Aegean Sea (northeastern Mediterranean)

The spatial structure and seasonal changes of the demersal fish assemblages on the continental shelf (100–200 m) and upper slope (200–500 m) in the North Aegean Sea (Northern Aegean and Thracian Seas, northeastern Mediterranean, Greece) were analysed. Seasonal experimental trawl surveys, carried out from summer 1990 to autumn 1993, provided a total of 151 demersal fish species. Analysis of 259 bottom trawls showed the existence of four groups associated with the continental shelf and the upper slope; each group was dominated by a small number of species. The bathymetric distribution of the species, established using measures of the centre of gravity and habitat width, revealed that most of the species had a wide distributional range within the study area, although a few were restricted to the greatest depths. Density, biomass, species richness and diversity decreased significantly with depth, and were also indicative of distinctive characteristics between these fish assemblages. Mean fish weight exhibited two different trends: a bigger-deeper phenomenon at the continental shelf and a smaller-deeper phenomenon at the upper slope. The variability in assemblage structure was determined mainly by depth and, to a lesser extent, by season and geographical location. For some species, results suggest a pattern of gradual species replacement along the depth gradient coupled with ontogenetic habitat shifts.     

奥茅卷转虫Ammonia aomoriensis(Asano,1951)与毕克卷转虫Ammonia beccarii(Linnaeus,1758)(有孔虫)的分类学以及在黄东海分布的温盐深特征比较研究

Ammonia aomoriensis(Asano,1951)和Ammonia beccarii(Linnaeus,1758)是两个形态学易混淆,但被广泛使用并具有重要环境指示意义的有孔虫。通过对渤海、黄海和东海陆架区60个站位表层沉积物的水平分布调查,并连续17个月对潮间带分低潮区和高潮区进行了季节调查,对二者的形态分类、生态分布和环境关系进行比较研究。结果表明A.aomoriensis和A.beccarii在潮间带的丰度都有季节性变化,体现冬高夏低的特点,前者一般在高潮区较多,后者在低潮区较多。二者的丰度从潮间带到陆架区随着水深的增加呈阶梯式锐减:平均含量分别达22%和39%;在水深<20m的陆架区平均含量分别降至15%和6%;在水深>20m的陆架区平均含量分别再次降至0.6%和1.4%。统计分析表明二者对盐度和水深的响应相似,但对温度的反应存在差异:在潮间带环境,二者的丰度都与盐度显著正相关;在浅海陆架环境,二者的丰度都与水深呈显著负相关;无论在潮间带还是陆架海区,A.beccarii的丰度都与海水温度呈显著负相关,但A.aomoriensis与温度相关性不显著。本研究结果显示A.aomoriensis和A.beccarii对滨岸浅海都具有优越的指示作用,在古环境分析中,首先可根据二者的含量进行环境推测(潮间带或者陆架浅海),再利用不同环境下本文所建立的线性方程对海水温、盐、深进行大体的估算。     

Stability of spatial pattern of fish species diversity in the Strait of Sicily (central Mediterranean)

In this paper, species diversity of demersal fish communities was analysed over an area covering about 45,000 km² of the Italian side of the Strait of Sicily (central Mediterranean). Fish abundance data come from a 10-year series (1994–2003) of experimental bottom trawl surveys carried out within the framework of the international program MEDITS. A simple GIS-based method was proposed to identify areas supporting high or low values of diversity and evaluate their temporal stability. A well-defined spatio-temporal pattern in diversity emerged from the analysis, with some areas of great ecological relevance being identified. Importantly, the greatest diversity within the fish communities was consistently seen at the offshore bank on the western part of the south Sicilian shelf (Adventure Bank). The site also supports high total biomass of demersal resources and shows the presence of species of great concern to fisheries. Results suggest that Adventure Bank represents a priority site for investigating the possibility of innovative management of marine ecosystems and demersal fisheries in offshore zones.     

Biodiversity of the deep-sea continental margin bordering the Gulf of Maine (NW Atlantic): relationships among sub-regions and to shelf systems

Background

In contrast to the well-studied continental shelf region of the Gulf of Maine, fundamental questions regarding the diversity, distribution, and abundance of species living in deep-sea habitats along the adjacent continental margin remain unanswered. Lack of such knowledge precludes a greater understanding of the Gulf of Maine ecosystem and limits development of alternatives for conservation and management.

Methodology/Principal Findings

We use data from the published literature, unpublished studies, museum records and online sources, to: (1) assess the current state of knowledge of species diversity in the deep-sea habitats adjacent to the Gulf of Maine (39–43°N, 63–71°W, 150–3000 m depth); (2) compare patterns of taxonomic diversity and distribution of megafaunal and macrofaunal species among six distinct sub-regions and to the continental shelf; and (3) estimate the amount of unknown diversity in the region. Known diversity for the deep-sea region is 1,671 species; most are narrowly distributed and known to occur within only one sub-region. The number of species varies by sub-region and is directly related to sampling effort occurring within each. Fishes, corals, decapod crustaceans, molluscs, and echinoderms are relatively well known, while most other taxonomic groups are poorly known. Taxonomic diversity decreases with increasing distance from the continental shelf and with changes in benthic topography. Low similarity in faunal composition suggests the deep-sea region harbours faunal communities distinct from those of the continental shelf. Non-parametric estimators of species richness suggest a minimum of 50% of the deep-sea species inventory remains to be discovered.

Conclusions/Significance

The current state of knowledge of biodiversity in this deep-sea region is rudimentary. Our ability to answer questions is hampered by a lack of sufficient data for many taxonomic groups, which is constrained by sampling biases, life-history characteristics of target species, and the lack of trained taxonomists.     

Distribution and relative abundance of main species of grenadiers (Macrouridae, Gadiformes) from the African Atlantic Coast

This study describes the geographic and bathymetric distribution patterns of abundance of the main macrourid species found in Atlantic African waters. A series of demersal trawl surveys, carried out in waters off Morocco, Western Sahara, Mauritania, Guinea Bissau, Gabon, Angola, and Namibia provided the catch data analysed. The survey area was between latitudes 35°56??N and 29°39.50??S and the sampled depths from 20 to 2000 m on the continental shelf and the slope. We collected 50 macrourid species belonging to 15 genera. The most abundant species was Nezumia micronychodon, with 91980 specimens caught, followed by Nezumia duodecim, Trachyrincus scabrus, and Hymenocephalus italicus with 31461, 28411, and 25349 specimens, respectively. The bathymetrical distribution ranges are extended for 21 species of grenadiers.     

The Current Status of Demersal and Pelagic Fish Stocks in the Olyutorsky-Navarin Shelf Area

Russian Journal of Marine Biology - Stocks of demersal and pelagic fish species in the near-bottom layer over the outer shelf and upper part of the continental slope between Cape Olyutorsky and...     

The Seasonal Relationship Between Meroplankton and Megabenthos on Georges Bank,Gulf of Maine,Northwest Atlantic

A broad based environmental study of Georges Bank included samples of zooplankton and dredge samples of megabenthos for four seasons. The purpose of this account is to examine the seasonal relationship between meroplankton and megabenthos. Mean densities of meroplankton were relatively high at shallow near shore stations and the central Bank and low at deeper stations. Densities were highest in the summer and lowest in the winter for major taxa. For megabenthos the number of species, relative abundance and relative biomass was also highest in the summer and lowest in the winter. Dominant megabenthos provided year round occupants and seasonal pulses. Year round occupants and seasonal peaks of some megabenthos facilitate year round foraging by demersal finfish enhancing the general production of the Bank. It was concluded that Georges Bank megabenthos was part of a broad ranging continental shelf, sand bottom fauna extending at least from Gaspe Bay to the offing of Chesapeake Bay.