The ICES International Bottom Trawl Survey (IBTS) quarter 3 (Q3) data, Dutch Beam Trawl Survey (BTS) Q3 data, and ICES stock assessment data were analysed to model the catchability of each 1-cm size class of demersal fish caught in the Q3 IBTS. Estimates of catchability were generally low, suggesting that raw trawl survey density data seriously underestimated actual densities.

No description available.

The purpose of this study is to establish the background metal concentrations of several demersal aquatic organisms in the coastal waters off Yunlin county before the development of petroleum industries camp at Tai-shi area, S. W. Taiwan. In addition to, the proper bioindicators are also investigated for future monitoring purpose. Twenty-seven species of sedimentary organisms, including 11 species of fishes, 3 species of crabs, 9 species of shrimps, 2 species of mollusca, and 2 species of cephalopods were collected in 5 seasons from September 1998 to November 1999. Metal concentrations of Ag, As, Cd, Co, Cu, Fe, Hg, Mn, Se and Zn were analyzed in the muscles and internal organs. The results showed that metal concentrations were significantly different according to species and tissues. Muscle concentrations of As, Fe and Zn were higher in fish, shrimp and cephalopod, whereas Zn, Cu and As were in crab, and Fe and Zn in mollusca. In the internal organs, Fe concentrations were the highest metal contents of fish and mollusca, but Cu were the highest for crab and shrimp. Nevertheless, Fe and Cu concentrations were respectively the highest elemental contents in two species of cephalopods, Octopus ocellatus and Sepiotenthis lessoniana. In gonads, Zn was the highest metal concentration in both gender of fish. However, in crab, Cu and Zn were respectively the highest metal concentrations of Portunus pelagicus and Charybdis hellerii. Among the all, Ag, Co, Cd and Hg showed the lowest concentrations in the species. In most cases, the metal concentrations of internal organs were higher than those of muscles, except Ag and Hg turned out to be reverse. The mean metal concentrations found in this study were similar to those measured in uncontaminated waters worldwide, so that it represents the background values of the aquatic demersal organisms in Yin-lin waters. The metal concentrations in the editable parts of the organisms were all below the food safety standard worldwide. Among the 10 metals analyzed, only As, Se and Zn concentrations of gonad showed the gender-differences. A positive correlation between a metal concentration and the body size were found in several cases, e. g. Ag in internal organs of Neverita lineata, As in muscles of Penaeus cornutus, Hg in muscles of Sillago sihama, Penaeus cornutus, Penaeus hardwickii and Neverita didyma, and Zn in hepatopancrea of Portunus pelagicus. However, Zn in viscera of Neverita didyma revealed a negative correlation to the size. Seasonal variations of metal concentrations were also found in the internal organs of most species. The concentrations of Cu, Fe, Mn, Se, Zn and As of internal organs showed a peak in both February and April, which may relate to the seasonal in put of anthropogenic pollutants in the area. Based on the metal concentrations of internal organs, the ratio of internal organ to muscle and the relative deviations, we suggest Octopus ocellatus, Portunus sanguinolentus (great for Ag, Cd, Co, Cu, Se and Zn), Penaeus cornutus (great for As and Cd), Neverita didyma(great for Co, Hg and Zn) and Arius maculatus(great for Fe, Se and Zn), which potentially concentrated high levels of metals, could be the good bioindicators in future.

Magister Scientiae (Biodiversity and Conservation Biology) - MSc (Biodiv and Cons Biol) / The objective of this thesis was to elucidate intra- and interspecific variability in the distribution patterns and diet of the two most common demersal catsharks taken as by-catch by the commercial trawling industry targeting the two Cape hake species off the West and South coasts of South Africa. Samples and data were collected during routine demersal hake biomass surveys conducted by DAFF, with distribution data collected from 1994 to 2015 and stomach content and stable isotope data collected from 2014 to 2015. On examination of the distribution data, Holohalaelurus regani was found to be more abundant on the West Coast and Scyliorhinus capensis was found to be more abundant on the South Coast. Both catsharks were observed to display size-based segregations, with catshark size increasing with depth in both species. Differences in the distribution patterns of male and female H. regani were also noted, with female catsharks inhabiting inshore areas and male catsharks inhabiting offshore areas. The two catsharks appeared to display high levels of dietary overlap, with individuals feeding on the most abundant crustaceans and cephalopods caught as by-catch in the trawl on each coast.

Made available in DSpace on 2014-06-12T23:02:01Z (GMT). No. of bitstreams: 2 arquivo8363_1.pdf: 969516 bytes, checksum: 819d753816ad2faf1e67e5a8a6c7c850 (MD5) license.txt: 1748 bytes, checksum: 8a4605be74aa9ea9d79846c1fba20a33 (MD5) Previous issue date: 2003 / Conselho Nacional de Desenvolvimento Científico e Tecnológico / Estudos na Área de Proteção Ambiental (APA dos Corais) de Tamandaré (PE) foram realizados com o objetivo de testar o uso de armadilhas na coleta do zooplâncton demersal, sendo também verificado o efeito da luz na migração dos organismos, a influência de diferentes tamanhos de malhas nas armadilhas, as diferenças sazonais, o efeito do tipo de substrato, a biodiversidade e o papel dessa comunidade na área recifal. As amostras foram obtidas em duas estações fixas (recife e cascalho), nos períodos chuvoso (julho/2000) e seco (janeiro/2001), sendo as amostragens em cada período feitas durante três dias consecutivos, em maré de quadratura. As 46 amostras do zooplâncton demersal foram obtidas através de oito armadilhas, em cada substrato, quatro das quais possuíam malhas de 125&#956;m (duas com luz e duas sem luz) e as outras quatro com malhas de 300&#956;m (duas com luz e duas sem luz). Essas armadilhas foram colocadas no local de coleta às 18h00 e retiradas às 06h00. Após as coletas as amostras foram fixadas com formol a 4%, neutralizado com bórax. Em laboratório, a biomassa foi obtida através da determinação do peso úmido. As análises qualitativas e quantitativas foram feitas sob microscópio composto. A temperatura variou de 24.0ºC a 25,25ºC no período chuvoso e de 27,00ºC e 28,80ºC no período seco. A salinidade variou de 31,60 a 33,70 no período chuvoso e de 30,69 a 32,0 no período seco. As armadilhas utilizadas em Tamandaré foram eficientes na coleta do zooplâncton demersal. A comunidade foi composta por organismos holoplanctônicos (56%), meroplanctônicos (15%) e ticoplanctônicos (29%) de origem oceânica e estuarina. A biodiversidade foi alta com 118 taxa, em decorrência da inclusão na comunidade zooplânctonica de grupos demersais. A composição do zooplâncton apresentou diferenças mínimas entre as amostras. Os copépodas destacaram-se nas armadilhas de 125&#956;m de abertura de malha e as larvas de crustáceos nas de 300&#956;m. A diversidade específica foi, geralmente, alta com valores maiores que 3bits.ind-1. A biomassa variou de 0,09 g.m-2 (período seco, armadilha 125 &#956;m) a 75,09 g.m-2 (período chuvoso, armadilha 125 &#956;m). A densidade zooplanctônica das armadilhas com malhas de 125&#956;m (~659.153,8 org.m-2) foram bem maiores que as de 300&#956;m (~186.483,6 org.m-2), embora não apresentando diferenças estatísticas significativas (p>0,005). As armadilhas sem luz apresentaram maior densidade, porém estatisticamente sem diferenças significativas (p>0,05). As maiores diferenças entre amostras coletadas em substratos recifal e de cascalho foi na densidade, com maior quantidade nos recifes, porém essas diferenças não foram significativas (p>0,05). Contudo, diferenças entre períodos seco e chuvoso foram significativas (p<0,05), sendo a biomassa maior no período chuvoso e a densidade no período seco, neste último grande quantidade de organismos de tamanho menor. As migrações tróficas noturnas por grande parte do zooplâncton demersal evidencia seu importante papel estruturador da comunidade recifal

Since the beginning of the Industrial Revolution, carbon dioxide (CO2) has been emitted into the atmosphere at rates unprecedented to Earth’s history. Nearly 30% of the anthropogenic CO2 in the atmosphere has been absorbed in surface waters of the ocean, pushing carbonate chemistry towards increased bicarbonate ions and hydrogen protons and decreased carbonate ions. Consequently, seawater pH has decreased from pre-Industrial Revolution levels of 8.2 to current levels of 8.1, and it is expected to continue to drop to 7.8 by the year 2100 if carbon emissions continue as predicted. The combination of these effects is referred to as ocean acidification. It is at the forefront of marine research as it poses a serious threat to several marine organisms and ecosystems. Ocean acidification has the most notable direct effect on calcifying organisms with calcium carbonate skeletons and shells, because fewer carbonate ions in the water column result in reduced calcification. Coral reefs are especially vulnerable to ocean acidification since reefs are composed of complex carbonate structures. Coral reefs have a high biodiversity; thus, not only will the corals themselves be affected by ocean acidification, but so will many of the animals that dwell in them. The primary objective of this thesis was to examine the effects of ocean acidification on demersal zooplankton that reside in coral reefs. Ocean acidification research on zooplankton has primarily been single- species experiments on calcifying species or generalist copepod species. Scaling-up to experiments examining ocean acidification effects on entire zooplankton communities is logistically difficult, thus the ability to predict community changes in zooplankton due to ocean acidification has been rather limited. However, a few locations around the world have submarine volcanic CO2 seeps that can be used as natural laboratories to study ecosystem effects of ocean acidification. Two CO2 seeps located in coral reefs in Papua New Guinea were used as windows into the future to examine the effects of ocean acidification on entire zooplankton communities while they live naturally in their environment. Over three expeditions to two CO2 seeps, nocturnal plankton were sampled with horizontal net tows and emergence traps. Additional experiments were also conducted, and collectively this work is summarized in chapters 2-5 as outlined below. Chapter 2 reports on the observed changes in zooplankton abundance and community composition between control and high-CO2 sites. Consistent results between seep sites and expeditions showed that zooplankton abundances were reduced three-fold under high-CO2 conditions. The abundance loss was partially attributed to habitat change within the coral reef, from more structurally complex corals in the control sites to a replacement of massive bouldering corals in the high-CO2 sites. The loss of structural complexity in the reef meant there were fewer hiding spaces for the zooplankton to seek refuge in during the day. All zooplankton taxa were reduced under high-CO2 conditions but to varying levels, suggesting that each taxon reacts differently to ocean acidification. Since each taxonomic group within the zooplankton communities was reduced to varying levels under ocean acidification, the copepod genus with the largest reduction in abundance was investigated in more detail. Labidocera spp. are pontellid copepods that are generally considered surface-dwellers and are not known to inhabit coral reefs. Therefore, as a preface to the ocean acidification study, the new discovery of these copepods living in coral reefs is first described (Chapter 3). Not only were they found to be residential to the reef, but Labidocera spp. living at the control reefs preferred to reside in coral rubble, macroalgae, and turf algae. Labidocera spp. were one of the most sensitive copepods to high-CO2 conditions and were reduced by nearly 70% in abundance, prompting a more detailed investigation about the effect of ocean acidification on their physiology and habitat preference (Chapter 4). Physiological parameters, e.g. size, feeding, and oocyte development, were unaffected by ocean acidification. Unlike the zooplankton community as a whole, the main cause for the abundance loss of Labidocera spp. was not a shift in the habitat because their preferred substrata were of equal percent coverage across high-CO2 and control sites. Instead, Labidocera spp. were no longer associated with any substrata type. Multiple direct and indirect effects of ocean acidification will act on each zooplankton taxa separately, and their collective response will contribute to the community response. The effects of ocean acidification on zooplankton communities were then scaled up to potential impacts on entire ecosystems. Zooplankton are the primary food source for corals, fish, and other zooplanktivores. The impacts of ocean acidification on zooplankton communities will have cascade effects on the food chain via the pathway of zooplanktivorous organisms. A case study on the stony coral Galaxea fascicularis explored the effects of ocean acidification on the ability of corals, which had lived their entire lives under high-CO2 conditions, to feed on zooplankton (Chapter 5). Under anthropogenic changes, whether it is from bleaching, high turbidity, or ocean acidification, some corals rely more on heterotrophy and consume more zooplankton. Contrary to expectation, this study showed that when given equal quantities of food particles these corals consumed less zooplankton under ocean acidification. Corals rely on heterotrophy for essential nutrients, like nitrogen and phosphorus, which they cannot otherwise obtain from autotrophy and their symbiotic zooxanthellae. In conclusion, my thesis shows that not only is there fewer zooplankton available to consume, but the existing zooplankton is consumed with lower capture rates under high CO2 conditions. Coral reefs in future oceans will likely have reduced zooplankton abundances as an indirect effect of ocean acidification, partially caused by a change in habitat from branching corals to more massive bouldering corals. Zooplankton abundances were reduced yet the community composition was unaffected by ocean acidification. All zooplankton taxa were reduced yet present under high-CO2 conditions suggesting that the zooplankton are at least able to survive under ocean acidification. Fewer zooplankton will be available to zooplanktivores, but the fatty acid content and nutritional value of the zooplankton as a food source is expected to be similar to current food. Together this is expected to negatively impact the entire coral reef ecosystem, with some coral species unable to consume zooplankton at normal rates. In an ecosystem already highly vulnerable to ocean acidification, coral reefs may be even more threatened if the very basis of their food webs is reduced.

Dissertação(mestrado) - Universidade Federal do Rio Grande, Programa de Pós–Graduação em Oceanografia Biológica, Instituto de Oceanografia, 2010. / Submitted by Cristiane Gomides (cristiane_gomides@hotmail.com) on 2013-12-16T02:03:18Z No. of bitstreams: 1 Paloma Lumi Costa.pdf: 5921417 bytes, checksum: f675464f8e1a0f393d83b8cfc5e4ed76 (MD5) / Approved for entry into archive by Sabrina Andrade (sabrinabeatriz@ibest.com.br) on 2013-12-18T18:15:15Z (GMT) No. of bitstreams: 1 Paloma Lumi Costa.pdf: 5921417 bytes, checksum: f675464f8e1a0f393d83b8cfc5e4ed76 (MD5) / Made available in DSpace on 2013-12-18T18:15:15Z (GMT). No. of bitstreams: 1 Paloma Lumi Costa.pdf: 5921417 bytes, checksum: f675464f8e1a0f393d83b8cfc5e4ed76 (MD5) Previous issue date: 2010 / O presente estudo teve como objetivo principal a realização de um mapeamento de fundo, através de metodologia acústica, para a região da Bacia de Pelotas e, de correlacionar tipos de substratos à diversidade e abundância de teleósteos demersais. O mapeamento foi realizado utilizando o parâmetro de refletividade da superfície do fundo, definido como a razão entre a intensidade acústica que atinge o leito marinho e é refletida pelo mesmo, registrando dessa forma características de fundo associadas a impedância do substrato. Os dados referentes a peixes foram obtidos na bibliografia ou disponibilizados por pesquisadores. Inicialmente foi realizado um estudo piloto em um setor costeiro da Bacia de Pelotas, Banco do Capela (RS), onde foram adquiridos dados de BSBS, posteriormente separados em quatro classes de valores: -5 a -10dB; -10 a -15dB; - 15 a -20dB e < -20dB. Um mapa com estas classes foi gerado por meio da interpolação dos valores BSBS e comparado a um mapa sedimentológico. Os resultados indicaram coerência para a classe de -15 a -20 dB, a qual foi predominante em áreas com a presença de sedimentos arenosos. No entanto, altos valores de refletividade foram encontrados nos setores mais costeiros onde o mapa sedimentológico apontou a predominância de sedimentos lamosos. Interpreta-se este resultado à presença de beach rocks presentes em sub-superfície. O passo seguinte foi a elaboração de um mapa de classes de BSBS utilizando dados referentes a quatro cruzeiros realizados em uma área da Bacia de Pelotas, em profundidades entre 100 e 1000 m, mapa este que apresentou coerência quando comparado a mapas sedimentológicos. Quatro feições com altos valore de BSBS foram identificadas entre as profundidades de 100 e 200m, a maior delas na altura do Cabo de Santa Marta e atribuídas principalmente a fundos consolidados ou com presença de material biodetrítico. Acima dos 500 m predominaram fundos com baixa refletividade acústica, atribuídos a presença de sedimento lamoso. Ao mapa acústico foram sobrepostas as ocorrências de nove espécies de teleósteos demersais cujas distribuições mostraram-se não aleatórias em relação às classes de refletividade acústica de fundo. Mullus argentinae, Nemadactylus bergi, Prionotus punctatus, Genypterus brasiliensis, Cynoscion guatucupa e Lopholatilus villarii ocorreram com mais freqüência e abundancia nas classes com menores valores de refletividade. Já o Pagrus pagrus teve maior abundancia e ocorrência em fundos com maiores valores de refletividade acústica, atribuídos a presença de sedimentos consolidados e biodetríticos. Posteriormente, o mapa foi analisado frente a informações de ocorrência de corais de profundidade, disponíveis na literatura. A comparação dos mapas gerados com base em informações dos corais de profundidade apresentou forte relação com áreas alta refletividade. / The main aim of this study was conduct a seabed mapping, using acoustic methods, in the region of Pelotas Basin and to correlate different types of substratum to the occurrence and abundance of demersal bonefishes. The map was created using the parameter BSBS, defined as the ratio between the acoustic intensity which reaches the ocean bottom and is backscattered and it is a function of the seabed surface acoustic impedande. Fish data were gathered from the literature or made available by researchers and overlaid to the map. Initially an experiment study was conducted in a coastal sector of the Pelotas Basin, Banco do Capela (RS) where BSBS data were acquired, post processed and grouped in four classes of values, namely: -5 to -10dB, -10 to -15 dB, -15 to -20dB and < -20dB. A map was created with these classes and compared with a sedimentological map. The results were consistent with in the class of - 15 to -20 dB, which was dominant and coincident with the presence of sandy sediments. However, high values of reflectivity were found in the most coastal sectors where the sedimentological map indicated the presence of muddy sediments. It is suggested that these results might be associated with the presence of beack rocks in the subbottom. Next was generated a map using BSBS data from four large scales cruises in the Pelotas Basin area, between 100 and 1000 m deep. This map was consistent when compared to sedimentological maps of the region. Four features with high acoustic reflectivity were identified between depths of 100 and 200 m, the largest in the Cabo de Santa Marta area. These features were attributed mainly to consolidated sediments or to the presence of biodetritus. Deeper than 500 m the map showed bottoms with low reflectivity associated to the presence of muddy sediments. To the BSBS map was overlayed the occurrences of nine species of demersal bonyfishes which showed not to be randomly distributed with relation to the BSBS classes. Mullus argentinae, Nemadactylus bergi, Prionotus punctatus, Genypterus brasiliensis, Cynoscion guatucupa and Lopholatilus villarii occurred more often and in higher abundances in classes with low values of reflectivity. In addition, Pagrus pagrus showed greater abundances and occurrences in higher acoustic reflectivity bottoms, related to the presence of biodetritus and consolidated bottoms. The acoustic map was also compared with the presence of deep sea corals as obtained from the literature. The comparison showed strong similarities among areas with high reflectivity identified in this work.

En Guinée, le constat a été établi par divers auteurs que l’intensification de l’exploitation des ressources démersales sur ces dernières décennies a induit une baisse générale de leur abondance. Cette intensification est supposée avoir induit également des modifications de la structure multi-spécifique et fonctionnelle des assemblages de poissons de cette zone, mais peu d’études ont permis d’en juger jusqu’ici, la plupart des travaux antérieurs sur ces ressources ayant concerné des approches strictement mono-spécifiques et des approches strictement taxonomiques. Dans ce contexte, l’objectif de cette thèse est de contribuer à un diagnostic écosystémique plus complet de l’état actuel des ressources marines guinéennes et de déterminer en particulier si la diversité taxonomique et fonctionnelle des assemblages de poissons a été affectée par la pêche.Les données de campagnes de chalutages scientifiques collectées sur le plateau continental guinéen entre 1985 et 2012, les statistiques sur les captures de pêche et dix-sept traits fonctionnels liés aux fonctions de locomotion et d’acquisition de nourriture de 50 espèces de poissons démersaux sont étudiés à travers divers indicateurs de diversité pour analyser l’impact de la pêche.Les résultats montrent que l’intensification de la pêche a eu des effets significatifs sur certaines caractéristiques générales du peuplement en question. Depuis 1985, on observe ainsi une baisse de la densité et du niveau trophique moyen des poissons ainsi qu’un turnover des dominances, par lequel les espèces principales, à forte valeur commerciale, caractérisées par des masses corporelles importantes et une croissance lente sont progressivement remplacées par des espèces de plus petites tailles à moindre valeur commerciale et à croissance rapide. On observe également une baisse significative de la richesse fonctionnelle dont l’évolution conforte les résultats obtenus à partir des évaluations taxonomiques et confirme que l’écosystème côtier du plateau continental est perturbé en lien avec la pression de pêche. / In Guinea, was highlighted by various authors that the intensification of the exploitation of demersal resources over recent decades has led to a general decline in abundance. This intensification is supposed to have also induces changes in the specific and multi-functional structure of the fish assemblages of this zone, but few studies have Judging far, most previous work on these resources with relevant strictly mono-specific approaches and strictly taxonomic approaches. In this context, the aim of this thesis is to contribute to a more complete ecosystem diagnosis of the current state of the Guinean marine resources and in particular whether the taxonomic and functional diversity of fish assemblages was affected by fishing. Data from scientific trawl surveys collected on Guinean continental shelf between 1985 and 2012, statistics on catches of fishing and seventeen functional traits related to locomotion functions and food purchase 50 groundfish species are studied diversity through various indicators to analyze the impact of fishing.The results show that the intensification of fishing has had significant effects on certain general characteristics of the population in question. Since 1985, we thus observed a drop in the density and the mean trophic level of fish and a turnover of dominance, whereby major species of high commercial value, characterized by substantial body masses and slow growth are gradually replaced by species of smaller sizes at lower commercial value and rapid growth. There is also a significant decrease in functional richness whose evolution confirms the results obtained from the taxonomic assessments and confirms that the coastal ecosystem of the continental shelf is disrupted in connection with fishing pressure.

Ecosystem-level changes have taken place in the Mediterranean Sea over the last decades due to both anthropogenic interferences and natural perturbations. Compared to the western Mediterranean Sea, influences of these factors especially on flora and fauna characteristics are much more dramatic and intense in the eastern part, particularly in the northeastern Levant Sea where the study area is located. In this study, life history traits of some core species (both native and immigrant) occupying the continental shelf of the northeastern Levant Sea were studied in this changing ecosystem to improve limited ecological understanding of the demersal fish assemblages of the northeastern Levant Sea. For this purpose, the annual patterns in allocation and utilization of energy in demersal fish species, temporal and bathymetrical trends in fish distribution with respect to biological requirements of the species and strategies adapted by the species in growth, reproduction and energy storage were investigated by examining growth parameters, biological indices and abundance and biomass variations. Influences of environmental variables on spatiotemporal distribution and biological characteristic of Mullus barbatus were also explored by generalized additive models. Biological data were collected at monthly intervals between May 2007 and May 2010 by trawl sampling while sample collection of environmental variables (temperature and salinity) was performed from December 2008 to May 2010. Results of this study reveal that the components of the demersal fish assemblage in the region fulfill their biological activities within a short period of time when the highest productivity is reached in the area. Moreover, results indicate that within this short period of time, some native components of the demersal fish assemblages studied (Mullus barbatus and Pagellus erythrinus) exhibit strategies such as fast growth, early maturation, short reproduction season, secondary spawners to cope with the environmental peculiarities. On the other hand, the successful exotic colonizers develop strategies as well but these successful immigrants also use time (Lagocephalus suezensis) and space (depth) (Upeneus pori) slot that the native species avoid. In some of the species examined (Mullus barbatus and Lagocephalus suezensis), growth is fast, sexual maturity is early, reproduction period is short, and reproduction potential is high. With the peculiar environmental condition, these life history traits are attributed to the &ldquo / r-strategy&rdquo / of the species. In this study, generalized additive models of Mullus barbatus explain 81.5 % variations in Gonadosomatic Index (GSI), 55.2 % in Hepatosomatic Index (HSI) and 43.9 % in Condition Factor (K). The time component in the GAM model captures the same cyclic pattern observed in GSI of Mullus barbatus. Besides, The GAM results suggest that the highest GSI values associated with the bottom water temperature are between 18 &ndash / 19 &deg / C while the partial effect of bottom salinity is at 38.7 psu. A positive effect of depth on GSI of the species starts after 60 meters depth and increasing trend continues until 125 meters depth and then decreases. The HSI results are almost identical to GSI outputs indicating that the effects of the parameters concerned act in a similar manner. The results of the GAM models failed to explain influence of environmental parameters on vertical and seasonal distribution of adult Mullus barbatus. However 83.5 % variances were explained in distribution of juveniles. The salinity and temperature have the highest impact on the distribution of juveniles among the parameters evaluated. The results indicate that the occurrence of Atlantic Water in the area has a positive influence on M. barbatus, particularly on the recruits through either by its low salinity or by another factor associated with this water mass. The vertical distribution range are set by the high temperatures (&gt / 27 &deg / C) at the shallow depths during summer and the low temperatures on the shelf break zone (&lt / 16 &deg / C). A comparison of vertical abundance distribution of Mullus barbatus and the vertical temperature variations indicate that the species may tolerate up to 27 &deg / C and then individuals move to the deeper depths so that to the cooler waters when the temperature exceeds their tolerance limit. As well as the life history traits adopted by the species, there are some other factors providing advantages to the species. The fisheries regulations, particularly the time limits applied in the area are in favor of the species especially of pre-recruits. In the study area the pre-recruitment phase and summer YOY aggregations in shallow waters of most species studied in this thesis take place during a time when the fishing season is closed.

The deep ocean (> 200-m depth) covers more than 65 percent of earth's surface and is known as the largest active carbon sink of the planet. Photosynthesis fixes inorganic carbon into organic rich-compounds to fuel the biological production in the upper ocean. A small portion of the photosynthetic carbon eventually sinks to the seafloor to support diverse deep-sea life. In this dissertation, the phytoplankton production and export flux of particulate organic carbon (POC) to the seafloor were linked to standing stocks and compositional changes of the deep-sea soft bottom assemblages. The pattern and processes of energy transfer from the surface ocean to the deep sea was examined by modeling the global benthic bacteria, meiofauna, macrofauna, and megafauna biomass from remotely sensed ocean color images and the seafloor relief. The analysis was then scaled down to the macrofauna of the Gulf of Mexico (GoM) to examine the global pattern on regional oceanic features with contrasting productivity regimes. These results suggested a universal decline of benthic standing stocks down the continental margins that is caused by an exponential decrease of export POC flux with depth. A revisit of historical epibenthic invertebrate sampling in the North Atlantic showed that both individual species and multi-species assemblages occurred in narrow depth bands that hugged the topography from the upper continental slope out to the Hatteras Abyssal Plain. The continuum compositional change suggested that the continuous decline of benthic food supply with depth was the potential driving force for the pattern of bathymetric faunal zonation. A broad, systematic survey across multiple depth transects in the northern GoM suggested that macrofauna zonation is not only taking place across isobaths, but also form the northeast to the northwest GoM due to a horizontal productivity gradient created by the nutrient-laden Mississippi River. Analyses of long-term demersal fish data from 1964 to 2002 in the northern GoM showed no evidence of large-scale faunal change across different sampling times. Base on the pooled data, a shift in rate of fish species replacement may be caused by complex biological interactions or changes in environmental heterogeneity along depth or productivity gradients.