Aquaculture is playing an important role in the development of fisheries in Vietnam, a role which has accelerated since 2000. Sustainability in aquaculture is receiving increasing attention, and this issue is not only the concern of government, but also stakeholders participating in the value chain. Therefore, this study aims to identify sustainability issues of farmed seafood by assessing the main sustainability issues raising concern. The Global Value Chain framework described by Gereffi et al. (2005) is applied for this study to explore the business relationships in supply chain and the perceptions of sustainability concerned by the value chain actors. A combination of qualitative and quantitative methods was used to collect data. An assessment of four species cultured on the Mekong Delta, the countries farmed seafood ‘hub’, found a clear distinction between species cultured with a local domestic market orientation (Giant Freshwater Prawn Macrobrachium rosenbergii; and Tilapia Oreochromis niloticus) and the two key export commodities - Striped catfish (Pangasianodon hypophthalmus) and Penaeid shrimp (Penaeus monodon & Litopenaeus vannamei). These orientations were based on a range of factors including the development of effective seed supplies and the cultural value of marketing in the live format. This study, conducted in ten provinces in the Mekong Delta from 2009 to 2013 had a focus on understanding the export-orientated commodities, striped catfish and shrimp through collection of baseline information on the value chain of farmed seafood, focusing on the farming sector, the actors and institutions involved and beneficiaries. Sustainability issues and perceptions of experts (top-down) and primary stakeholders (bottom-up) opinions were assessed through participatory workshops. Shrimp and striped catfish production are mainly farmed for export, with 83% and 95% of its production, respectively, leaving the country mainly after processing. Currently, mainly families operate small-/medium-scale farms; while large-farms are integrated within seafood processors. Production efficiency of large-farms tends to be better than small-/medium farms. Many striped catfish and shrimp farms are likely to reach several standard criteria such as economic feed conversion ratio (eFCR), stocking density, no banned chemical/drug and wild-seed use, and land property rights; however, there were still many standard criteria that existing farms could not meet such as effluent management, farm registration, fishmeal control, farm hygiene and record-keeping requirement. Hence, current farming practices, especially small-/medium farms have a long way to go to meet emergent international food standards. Recently, many small-/medium catfish farms faced problems with low fish prices, so they have had to cease catfish farming activities and temporarily stop farming; while some larger farms also had to temporarily stop farming. Therefore, fish price has tended to be a main driving force for catfish farm changes. In the shrimp industry, there were technical changes occurring in the high intensity level of shrimp farms (HiLI); whereas, the remaining shrimp farms had fewer changes in farm management. Most HiLI shrimp farms were affected by AHPNS disease, which was a main factor driving their farm changes. Many perceptions of sustainability were identified by stakeholder groups, however seven sustainability issues had a high level of agreement among stakeholders including input cost, capital & credit costs, unstable markets, government regulation & policy, disease, seed quality, water quality and water availability factors. Hatcheries, farmers and manager groups were more concerned about environmental issues; while for the input suppliers and processors, economics was the main issue. Farmers and processors were two main actors that played an important role in the production process of the value chain. Small-/medium farms dominated the number of farms overall and still played an important role in primary production. However, small-scale farms were considered as more vulnerable actors in the value chain, and they faced more difficulties in meeting increasing requirements on food quality/safety. To maintain the position in the value chain, the solutions could be horizontal and vertical coordination. Thus policy makers will need to find ways to include them in the planning processes. To reach sustainability will require the efforts of direct stakeholders, the role of the state agencies is essential in negotiation and diplomacy to create partnerships with the seafood importing countries. However, efforts to develop sustainable production become impossible without participation from importers, retailers and consumers.

The giant freshwater prawn, Macrobrachium rosenbergii (De Man, 1879), is gaining popularity as a key aquaculture species; global production currently exceed 220,000 tonnes, however, industry expansion is limited by high operational costs, with the feed accounting for between 40 to 60% of these. Attention, therefore, has been devoted to increasing the inclusion of plant proteins into the formulation of aqua feeds as a consequence of the limited, unpredictable supply and increasing price of fishmeal. The concomitant introductions of anti-nutritional factors (ANFs), such as phytic acid (PA) with the plant protein fraction, however, are major impediments in the efforts toward the increased use of plant protein ingredients in aqua feeds. Phytic acid is an anti-nutrient that can curtail the development of this as PA has been reported to suppress growth impairing proper nutrient intake, diminishing the availability of minerals, and causing damage to the body tissues and organs which can result in mortality. Although the anti-nutritive effects of PA have been studied extensively in terrestrial agriculture farm species, as well as in a variety of fish species, there is almost no information regarding the effects of PA in crustaceans, including the freshwater prawn, M. rosenbergii. The aims of this present thesis were, therefore, to gain a greater understanding of dietary PA and microbial phytase and their effect on growth performance, feed utilisation, nutrient utilisation and digestibility, mineral availability and whole body proximate composition in juvenile M. rosenbergii. Specifically, the first major experiment set out to investigate the effect of including increasing amounts of PA in the diets presented to M. rosenbergii on growth. The dose-response relationships between PA and growth performance, feed utilisation, nutrient digestibility and utilisation and whole proximate composition were investigated. Four replicate groups of M. rosenbergii with a mean initial carapace length of 6.03 ± 0.30 mm and mean initial weight of 0.29 ± 0.02 g were fed graded levels of PA for 140 days. The basal diet, to which different levels of PA were added to obtain 0.26 (control), 6.48, 11.28, 16.53, 21.45 and 26.16 g PA kg-1, contained fishmeal, soy protein concentrate, wheat meal and corn starch. The results indicated that growth performance, feed utilisation and survival did not differ significantly between the groups receiving the different inclusions of PA within their diets. The apparent protein, lipid and energy utilisations responded negatively, decreasing significantly (p<0.05) with an increasing inclusion of PA, particularly within the groups of prawns fed the diet with the highest inclusions of PA, i.e. the 21.45–26.16 g PA kg-1 diets. The digestibility of protein and lipid were also reduced as the inclusion of PA increased. The whole body composition of protein (p<0.04), lipid (p<0.01) and gross energy (p<0.05) decreased significantly with an increasing supplementation of PA, while the ash content significantly increased (p<0.01), most notably in the groups of prawns receiving the highest levels of dietary PA. The second major experimental trial investigated the effect of microbial phytase on the growth of juvenile M. rosenbergii, when fed diets supplemented with various doses for a period of 80 days. The study set out to improve the growth performance, feed utilisation, nutrient digestibility and utilisation and body composition of M. rosenbergii when fed diets high in plant protein ingredients. To investigate this, four plant protein based diets, which included soybean meal, wheat gluten and wheat meal, were formulated and supplemented with microbial phytase at levels of 0, 500, 1000 and 2000 FTU kg-1 (one phytase unit per kg) and fed to sixty juvenile M. rosenbergii (mean initial carapace length of 8.51 ± 0.52 mm; mean initial weight of 0.40 ± 0.07 g) for 80 days. High levels of plant protein in the diets supplemented with 0–2000 FTU kg-1 did not result in any negative effect on growth performance, feed utilisation nor on the survival of M. rosenbergii. Noticeable moderate growth improvements in line with increasing microbial phytase supplement levels were observed and the highest growth performance was seen in the group fed 2000 FTU kg-1. Supplementation of the diets with 500–2000 FTU kg-1 were found to affect the nutrient utilisation, resulting in a significant (p<0.05) increase in the protein and lipid utilisation when compared to the prawns analysed from the control group. In addition to this latter finding, an increasing supplement of phytase in the diet also resulted in an increase in the dry matter fraction as well as improvements in the digestibility of protein and lipid. There were, however, no significant differences in moisture, protein, lipid, gross energy and the ash content of the whole body of the M. rosenbergii among the groups. This thesis, in a third major trial, explored the impact of other potential ANFs associated to PA, the binding effect of PA with mineral. The effects of graded levels of PA (i.e. 0.26–control, 6.48, 11.28, 16.53, 21.45 and 26.16 g PA kg-1) on the moult frequency and mineral availability in juvenile M. rosenbergii fed over a period of 140 days were determined. The levels of PA assessed in this feed trial had no major detrimental effects on moult frequency. Negative effects (p<0.05) of high PA levels (i.e. 21.45–26.16 g PA kg-1), however, were found on the whole body P concentration. An inverse trend was recorded for the Ca content in the whole body (p<0.005) and carapace (p<0.004) with increasing PA inclusion. These results are consistent with findings for marine shrimp species such as Marsupenaeus japonicus and Litopenaeus vannamei. The graded inclusion of PA in the experimental diets also resulted in a significant reduced (p<0.03) P content in the carapace. Significant changes (p<0.05) were observed in the carapace Zn, Cu, K and Na compositions, particularly in the prawns fed the diet containing 11.28 g PA kg-1, which suggests that the specific minerals were either selectively utilised or retained in the carapace. Accordingly, this thesis investigates the potential of adding dietary supplements of microbial phytase in order to improve mineral availability as proven in several fish species. To explore this, four experimental diets were formulated - three incorporating different levels of microbial phytase (i.e. 0 FTU kg-1, 1000 FTU kg-1 and 2000 FTU kg-1) and a fourth, a control. An aliquot of 15 g PA kg-1 was also added to each treatment. The mineral premix was omitted from the test group diets except the control diet was identical to the 0 FTU kg-1 diet but included a mineral premix and an aliquot of 8 g kg-1 monosodium phosphate which replaced an equal amount of wheat meal fraction. The trial found no significant differences in growth, feed utilisation and moult frequency with the microbial phytase level within the diet, however, survival was compromised. The proximate composition of the prawn whole body was in most cases unaffected by the level of phytase. Supplementation of the diets with microbial phytase did, however, result in significant higher (p<0.05) concentrations of minerals including: 1) Ca, Mg, K and Na in the whole body; 2) Ca and Zn in muscle tissue; and, 3) Ca and Mg in the carapace. The Zn content of the carapace, however, was negatively affected by the inclusion of microbial phytase suggesting the necessity of this mineral within the diet of M. rosenbergii. This thesis contributes to current understanding surrounding the inclusion of dietary PA and the benefits of microbial phytase within the experimental diets consumed by juvenile M. rosenbergii. The knowledge gained from this work provides a means to optimise the use of plant protein ingredients and with the potential to decrease the dependability of fishmeal without compromising M. rosenbergii production and profitability, thus ultimately promoting the sustainable expansion of M. rosenbergii aquaculture.

For decades, humans have impacted marine ecosystems in a variety of ways including contamination by pollution, fishing, and physical destruction of habitats. Global change has, and will, lead to alterations in in a number of abiotic factors of our ocean in particular reduced oxygen saturation, salinity changes, elevated temperature (ocean warming or OW) and elevated carbon dioxide (ocean acidification or OA). Now and in the future, OA and OW will operate together with local anthropogenic drivers such as oil pollution. And yet, at present, very little is known about their potential combined interactive effects on physiological performance and tolerance of marine organisms. Therefore, multiple driver experiments are required if we are to understand and predict future vulnerability of species, populations and ecosystems. Early life stages of invertebrates are generally considered most vulnerable to environmental stress. However, few studies consider the combined effects OA and OW on survival and growth during early development of marine invertebrates, and to our knowledge, there is no information on the additional effects of oil pollution. Therefore, the aim of this thesis was to investigate the effects of combined exposure to OA, OW, and incorporating local drivers such as oil pollution on the development, morphology and physiology of three economically and ecologically important marine invertebrates. These are Northern shrimp Pandalus borealis, Northern krill Meganyctiphanes norvegica, and the green sea urchin Strongylocentrotus droebachiensis. All are cold-water species, assumed to have a narrower tolerance than more temperate species, and so could be particular sensitive to combined stressor affects. Both Northern krill and to a lesser extent Northern shrimp larvae survived experimental conditions, mirroring those predicted under a future global change scenario (combined OA and OW exposure). Neither was hatching success affected. Both shrimp and krill larvae exhibited accelerated developmental rates and incurred greater maintenance costs as a result of exposure to these stressors. Shrimp larvae showed accelerated developmental rates (-9 days), increased metabolic rates (+20 %), and increased feeding rates (+20 %), but reduced growth (- 9 %) when exposed to OW compared with the control. OA increased development rate but only at the control temperature. Although juvenile mortality of krill was not affected by predicted OA/OW conditions, metabolic rate increased significantly (+ 36 %), as did larval developmental rate, while number of moults, feeding rate and growth (- 67 %) decreased significantly (- 67 %, - 60 % and -8 % respectively). Accelerated development was accompanied by greater maintenance costs possibly due to experience a mismatch between energy supply and demand. Both species had an excess of food, and so growth reduction was more likely to be associated with higher metabolic demands in the future global change treatments. Food shortage in situ, due to variable food availability in the sea and/or mismatch with key prey species (algae and zooplankton) could result in more negative effects on growth and ultimately survival. Green sea urchins were also able to survive OA exposure, without detectable effects on hatching success. However, at day 44 post-fertilization, larval body length in the OA treatment was 9 % lower compared to the control. Furthermore, there was a significant tendency of urchin larvae to increase swimming activity in the OA conditions that might indicate compensatory feeding. Elevated maintenance and repair costs as a result of exposure to multi-stressors affected the energy budget of all the three species studied here resulting in reduced growth. Global drivers (OA and OW) resulted in trade-offs with more energy reallocated to swimming activity and metabolism, rather than growth. Exposure to oil reduced the acquisition of energy by reduced feeding which in turn resulted in less energy being available for growth. Both shrimp and sea urchin larvae showed reduced activity and feeding when exposed to oil. It is possible that the reduced swimming activity observed may be due to a narcotic effect of the oil. Furthermore, early stage sea urchin larvae showed increased mortality when exposed to oil while the older larvae did not, indicating a stage specific toxicity to oil for sea urchin larvae. The combination of global drivers and oil pollution acted additively on growth for both sea urchin and shrimp larvae. The impact of combined drivers on the size of shrimp larvae was equal the sum of the negative impacts observed for each driver: a 5 % reduction when exposed to OA and OW, a 9 % reduction when exposed to oil, and a cumulative 15 % reduction when exposed to all stressors. Similarly, the impact of combined drivers on the size of sea urchin larvae was equal to the sum of the negative impacts observed for each driver: a 14 % reduction when exposed to OA, a 9 % reduction when exposed to oil, and a 21 % reduction when exposed to all drivers. Therefore, the study demonstrated the additive physiological effects of OA, OW and a contaminant, and indicated that larval (sea urchin and shrimp) resilience to future changes (i.e. pollution) could be greatly reduced if larvae were already energy limited and severely stressed (reduced development) as a result of exposure to the global drivers. This study therefore shows the importance that the effective management of local drivers such as oil pollution could have against the backdrop of OA and OW, and emphasises that it is important to study impacts of toxicants, such as an oil pollution, in the context of predicted changes in the environment, as OW and OA are becoming major concerns. Finally, the fact that some local and global drivers seem to act additively should encourage local managers to act on local driver regulations, to obtain positive effects on local populations and environment and thereby rendering them more resilient to the negative impacts of future global drivers.

The distribution of Callianassa kraussi in southern Africa extends from Lamberts Bay on the west coast to San Martinho in Mocambique. This represents a northerly extension of the range from the previous known limit of Inhaca Island. In this area 59 localities were visited and records obtained for an additional 16. Three areas were selected for detailed study. These were the west Kleinemonde estuary, which is normally closed off from the sea by a sand bar and the open Swartkops estuary both on the southeastern Cape coast, and the Swartvlei system, which consists of a lake connected to the sea by a channel which closes intermittently, on the southern Cape coast. The nature of the burrows constructed by C. kraussi was investigated in these areas. Burrow complexes may have up to nine entrances but more commonly two to four. Laboratory studies suggest that the number of entrances does not exceed the number of prawns present and consequently burrow opening counts will give an estimate of population density. Water movement can result in the closing off of burrows while strong water and sand movement will exclude C.kraussi from an area. C.kraussi is also excluded from areas which have very coarse substrates. A three year regular sampling program showed that C.kraussi breeds mainly in winter/spring with a smaller breeding peak in summer. Egg development time at 20°C in a salinity of 35° /₀₀ is 30-33 days. There are two larval stages which last 3-5 days. Development time of the eggs is tripled at temperatures of 13-15°C while larval development time is extended to 9-14 days. Development is possibly slightly accelerated at 25 ± 3°C but the number of eggs hatching is markedly reduced. Larval development times were similar to those at 20° and 35°/₀₀. There are no planktonic larval stages. Growth was more rapid and greater size was attained in the open Swartkops estuary than in the closed Kleinemonde estuary. Prawns hatching in winter/spring breed for the first time in the following summer at an age of about 16 months and then again in the following winter/spring at an age of about 2 years. Prawns hatching in summer breed in the following winter at an age of about 18 months and then again in the immediately following summer. Longevity in both sexes is about 2 years. Dispersal is accomplished by migration of the post-larval juvenile phases at an age of 3-5 months. Non-selfmaintaining populations exist in areas where salinities are too low to permit breeding. Population densities were found to vary markedly in different areas. Investigations of osmotic and ionic regulation showed that C.kraussi is a strong hyper-regulator and thus distinct from any other known species in the genus. Volume regulatory ability is well developed and depends on variable rates of urine production. Salt loss in dilutions occurs almost equally via the gills and the urine. The general responses of C.kraussi to dilutions of sea water are discussed. Various suggestions for conservation measures based on the distribution and iife cycle of C.kraussi were made. The factors affecting the distribution of C.kraussi are discussed. The problem of the larval development in C.kraussi was discussed in relation to reviews of larval types of benthic invertebrates. The importance of the burrow, the possible route by which C.kraussi has invaded estuaries and the differences between open and closed estuaries as shown by the effects on C.kraussi were discussed.

In South African estuaries the anomuran mud prawn, Upogebia africana (Ortmann), is the main organism exploited as bait by recreational and subsistence anglers. In the Knysna estuary, three groups of bait collectors were identified on the basis of their source of income: subsistence fishermen who rely on bait-collecting and fishing for their income, supplementary anglers who catch fish to supplement their income and leisure anglers who draw no income from fishing. Two groups were identified based on the methods used: lelsure anglers who collect bait using a prawn pusher or pump and fish using a fishing rod and tackle, and non-leisure anglers who collect mud prawns using tin cans and fish with handlines. The hypothesis was erected that bait-collecting does not affect the U africana populations in the Knysna estuary. The approach adopted was to assess the distribution, density, population structure and reproductive patterns of the bait stock and to estimate the intensity of bait collection, to test the validity of the hypothesis. U africana has an extensive distribution, occupying 62 % of the available intertidal area of the Knysna estuary. Mud prawns have a broad intertidal distribution from the high water level (Spartina zone) to the shallow subtidal. The density, biomass and population structure of the mud prawns vary significantly with distance up the estuary and with tidal height on each shore. The Invertebrate Reserve supports very low densities of U africana (x = 11.7 m⁻²), whereas a relatively inaccessible centre bank in the middle reaches of the estuary appears to be a very effective natural mud prawn reserve as it supports the highest densities (x = 176.5m⁻²). The mud prawn stock of the estuary is estimated to be 2.19 x 108 prawns (82.7 tonnes dry mass). The numbers of bait collectors present per mudbank is highest on public holidays (x = 34) and higher during the summer holidays (x = 16) than during the winter (x = 4). A total of 1.858 x 106 U africana or 700.53 kg (dry mass) are removed by bait collectors annually from the 6 popular bait-collecting sites studied. This represents 8.49 % of the mud prawn stocks at these sites and 0.85 % of the entire estuary stock. 85 % of the U africana taken as bait annually, is removed by the 77.12 % of bait collectors who are non-leisure anglers. Recreational or leisure anglers are responsible for removing 14.2 %. The reproduction of female U africana in the Knysna estuary is seasonal and occurs from late July to April. There is evidence that this breeding season consists of two merging breeding cycles. The largest percentage (63 %) of ovigerous females is found in the middle reaches of the Knysna estuary at the Oyster Bank where the highest numbers of stage 1 larvae (165 m⁻³) are released. Larvae were exported from the estuary on the crepuscular ebb tide with peaks in abundance of nearly 1500 m⁻³ in November 1995 and January 1996. Although numbers caught are not significantly higher, larvae are nearly twice as abundant on crepuscular neap tides following a new moon (waxing quarter) than on those following a full moon (waning quarter). Recruitment of juvenile U africana to populations in the estuary was highest in December (45 m⁻²) and decreased over the summer. The highest numbers of recruits (31 m⁻²) were found at those sites closest to the mouth or on the main channel. Recruitment to the Leisure Isle and Thesens sites which are intensively exploited by bait collectors is high (20 - 32 m⁻²). The number of juveniles recruiting to U africana populations is estimated to be four times as high as the numbers of mud prawns taken by bait collectors. Legal methods of bait collection used in the Knysna estuary by the majority of anglers appear to cause minimal sediment disturbance and are not likely to affect the associated infauna. Illegal bait-collecting methods are however highly destructive and must be prohibited. It is concluded that the null hypothesis is acceptable, as mud prawn stocks of the Knysna estuary are not over-exploited and appear to be naturally regulated. The recruitment rate of juvenile U africana is estimated to be sufficiently high to sustain the present levels of exploitation.

published_or_final_version / abstract / toc / Ecology and Biodiversity / Master / Master of Philosophy

The crayfish plague pathogen, the oomycete Aphanomyces astaci, has been decimating populations of European crayfish species for more than 150 years, and is therefore considered one of the 100 worst world's invasive species. A. astaci is highly specialised for a parasitic life, but it can be isolated from moribund crayfish and grown on synthetic media, as it is the case also for several other oomycetes (chapter 7). The life of A. astaci includes three basic forms: mycelium in host's tissues, and the infective units occurring in water, zoospores and cysts. All North American crayfish species tested so far have shown some resistance to A. astaci, i.e., they could carry the infection for long, serving as vectors of the pathogen. Massive sporulation from infected North American crayfish starts when the host is moulting, stressed, or dying (chapter 4). However, I could show in my experiments that some sporulation occurs even from apparently healthy and non-moulting American crayfish hosting A. astaci, so infected North American crayfish must be considered a permanent source of the infection (chapter 4). Five genotype groups of A. astaci have already been distinguished. Strains from a particular genotype group probably share the same original host crayfish species of North American origin. Nevertheless, they can...

Thesis: Ph. D., Joint Program in Oceanography/Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Department of Biology; and the Woods Hole Oceanographic Institution), 2017. / Cataloged from PDF version of thesis. / Includes bibliographical references. / Every genome tells a story. This dissertation contains four such stories, focused on shared themes of marine population dynamics and rapid change, with an emphasis on invasive marine species. Biological invasions are often characterized by a range expansion, during which strong genetic drift is hypothesized to result in decreased genetic diversity with increased distance from the center of the historic range, or the point of invasion. In this dissertation, population genetic and genomic tools are used to approach complex and previously intractable fundamental questions pertaining to the non-equilibrium dynamics of species invasions and rapid range expansions in two invasive marine species: the lionfish, Pterois volitans; and the shrimp, Palaemon macrodactylus. Using thousands of loci sequenced with restriction enzyme associated DNA sequencing in these two systems, this research tests theoretical predictions of the genomic signatures of range expansions. Additionally, the first chapter elucidates patterns of population genetic connectivity for deep-sea invertebrates in the New Zealand region demonstrating intimate relationships between genetics, oceanographic currents, and life history traits. Invasive shrimp results extend our understanding of marine population connectivity to suggest that human-mediated dispersal may be as important - if not more important - than oceanographic and life history considerations in determining genetic connectivity during specific phases of marine invasions. In invasive populations of lionfish, measures of genomic diversity, including a difference between observed and expected heterozygosity, were found to correlate with distance from the point of introduction, even in the absence of spatial metapopulation genetic structure. These results indicate a signal of rapid range expansion. The final study in this dissertation uses an innovative temporal approach to explore observed genomic patterns in the lionfish. In all, this dissertation provides a broad perspective through the study of multiple species undergoing superficially parallel processes that, under more intense scrutiny, are found to be mechanistically unique. It is only through comparative approaches that predictable patterns of population dynamics will emerge. / by Eleanor Kathleen Bors. / Ph. D.

O camarão corrupto Callichirus seilacheri foi erigido por Bott (1955) através de uma breve e incompleta descrição carente da maioria das ilustrações sobre as principais estruturas corporais desta espécie. Callichirus seilacheri é considerada, atualmente, como o único representante do gênero Callichirus na costa do Pacífico Leste. Sua distribuição geográfica abrange um amplo gradiente latitudinal de aproximadamente 50º graus (~13º N - 37º S) desde a praia Los Blancos (localidade-tipo), El Salvador até Lenga na costa de Chile. O estado taxonômico da grande população de C. seilacheri tem sido questionado no passado em reiteradas oportunidades. Este questionamento tem relação com a falta de estudos taxonômicos associados com estas populações e com o fato que alguns antecedentes moleculares têm demonstrado que as populações de Callichirus da costa do Pacífico de Nicarágua e México são diferentes. Considerando estes antecedentes, o primero objetivo do presente estudo foi avaliar o estado taxonômico de C. seilacheri na costa do Pacífico Leste da América Central. Para isto, foi coletado material de C. seilacheri em diferentes localidades da costa do Pacifico de América Central, incluindo a localidade-tipo desta espécie na costa de El Salvador. Conforme as observações morfológicas do material coletado, os caracteres diagnósticos de C. seilacheri incluem entre outros aspectos: (i) pedúnculos oculares com uma alongada projeção pré-córneal, cujas pontas divergem lateralmente; (ii) segmentos terminais do pedúnculo antênular e antenal com as bases paralelas; e (iii) pereiópodo maior do primeiro par de pereiópodos dos machos adultos com o mero armado de um lóbulo retangular na região ventral anterior e ísquio curvado para baixo com um gancho na margem ventral. Uma das descobertas mais relevantes foi que todas as fêmeas de C. seilacheri têm ambos gonóporos masculino e feminino, o qual representa o primeiro registro de intersexualidade no gênero Callichirus. O segundo objetivo desta tese foi avaliar se a espécie da costa chilena Callichirus garthi (Retamal, 1975), considerada como uma sinonímia-junior de C. seilacheri da costa do Pacífico da América Central, é uma espécie válida. Para isto, comparou-se o material-tipo de C. garthi e outros lotes desta espécie coletados ao longo da costa de Chile (~18º e 37º S) com os espécimes de C. seilacheri coletados na localidade-tipo (Playa Los Blancos, El Salvador) e em outras localidades da América Central. A comparação morfológica revelou importantes diferenças morfológicas entre os tipos morfológicos identificados em ambas espécies. Entre as principais diferenças e possível mencionar que C. garthi possui as pontas dos pedúnculos oculares paralelas, enquanto que em C. seilacheri são divergentes formando um angulo de 60-70°. Os machos adultos de ambas espécies compartilham quelípodos desiguais na fase adulta, mas somente, C. seilacheri tem um gancho sobre a margem ventral do ísquio e um lóbulo meral retangular. A analise morfológica do material biológico coletado em ambas regiões permite concluir que os espécimes coletados ao longo da costa do Chile pertencem à C. garthi, enquanto que os exemplares coletados na costa do Pacífico da Costa Rica pertencem à espécie C. seilacheri. Conforme a essas informações, C. garthi é uma espécie válida. Portanto, sugere-se a separação da grande população de C. seilacheri em duas diferentes populações: (i) uma pertencente ao C. seilacheri a qual ocorre desde a costa do El Salvador ate Costa Rica (~19º N 08º N), (ii) outra pertencente ao C. garthi a qual ocorre entre os 18º S e 37º S da costa chilena. A hipótese do centro abundância (HCA) é baseada na suposição de que as retricções fisiológicas limitam o desenvolvimento das populações nas bordas do seu intervalo de distribuição. Com o intuito de testar a validez desta hipótese, espécimes da espécie modelo Callichirus garthi foram coletados em sete populações distribuídas ao longo da costa chilena. Em cada população foram avaliados a densidade junto com uma serie de atributos populacionais de C. garthi (e.g. tamanho máximo do corpo, razão sexual, etc). Os principais resultados revelaram que C. garthi foi significativamente menos abundante nas populações locais, perto do centro e aumentou para as bordas norte e sul da sua distribuição na costa do Chile. No extremo sul e norte da distribuição, a estrutura da população foi composta por indivíduos de todos os tamanhos, em contraste com às localidades do centro, onde os indivíduos estavam concentrados em uma faixa de tamanho mais estreita. Surpreendentemente, nas bordas (norte e sul), à razão entre os sexos foi estremamente equilibrada. A abundância local foi levemente correlacionada com a distância entre cada localidade e o rio mais próximo e foi fortemente correlacionada com a estrutura da população. Aparentemente, a proximidade de um rio oferece as condições ideais para que C. garthi forme populações densas e equilibradas, o qual seria um reflexo do sucesso a nível individual que esta espécie atinge em direção às bordas. O modelo de distribuição de abundância de C. garthi pode ser considerado como uma exceção nas populações naturais devido que na maioria dos estudos prévios nesta matéria o modelo usualmente reportado é o modelo normal de abundância para um dos extremos. As generalizações acerca do padrão reprodutivo dos invertebrados bentônicos costeiros propõem que as espécies tropicais tenham reprodução do tipo continua, como reflexo das baixas oscilações térmicas ao longo de todo o ano (hipótese de Orton). Com o propósito de testar esta suposição em um ambiente tropical da América, foram realizados durante um ano amostragens mensais em uma população de C. seilacheri da costa do Pacífico de Costa Rica (América Central). Os resultados revelaram que C. seilacheri tem uma marcada sazonalidade reprodutiva, a qual contradiz os padrões esperados em regiões tropicais. As fêmeas ovígeras estiveram presentes desde maio até novembro, o que está estatisticamente relacionado com a diminuição da salinidade durante a estação chuvosa. A temperatura não teve influência sobre a periodicidade reprodutiva. Aparentemente, à reprodução em C. seilacheri está fortemente relacionada com a variabilidade climática da costa do Pacífico na Costa Rica, sendo desencadeada por oscilações na salinidade. Uma comparação entre C. garthi da costa chilena e C. seilacheri da costa do Pacífico da América Central revelou importantes diferenças na produção de ovos. Callichirus seilacheri produz uma media de quatro menos ovos e menores que C. garthi da costa do Chile. A variabilidade nas características reprodutivas (produção e tamanho dos ovos) e de tamanho corporal dos indivíduos observada nestas duas espécies de camarões corruptos sugerem a imposição de importantes restrições fisiológicas dadas principalmente por a temperatura em ambas às regiões da América. Os aspectos examinados no presente estudo constituem novos antecedentes sobre a taxonômia, morfologia e ecología em um dos gêneros da família Callianassidae mais representativos nas praias de areia da América. Cada um destas informações pode ser considerado de especial relevância para a conservação das populações de C. garthi e C. seilacheri no Pacífico Leste. Especialmente, porque ambas espécies são frequentemente recolhidas como isca para a pesca comercial e esportiva em algumas pequenas vilas costeiras. / The ghost shrimp Callichirus seilacheri was erected by Bott (1955) through a brief and poorly illustrated description. This species is considered as the only one current representative of genus Callichirus along the eastern Pacific. Their distribution encompasses approximately 50 degree of latitude, from Los Blancos, El Salvador (13º N) to Lenga, Chile (37º S). The identity of the large population of C. seilacheri along the Pacific coast of Americas has been questioned by different researchers whom have indicated the existence of more than one species of Callichirus for the Pacific coast of Mexico and the Pacific coast of Costa Rica and Nicaragua. Considering this information, the first focus of this thesis was realize a redescription of C. seilacheri based on specimens collected in different localities from Central America, including the type-locality of this species. According to the observations, the diagnostic features of C. seilacheri include (i) the eyestalks with elongated precorneal projection with tips diverging laterally; (ii) terminal segments of antennular peduncle and antennal with the parallel base and (iii) adult male with larger cheliped with rough rectangular lobe over anterior ventral margin of merus, ischium curved downward with a hook on ventral margin. All females analyzed herein have both male and female gonopores, thus firstly recorded the presence of intersex within the genus Callichirus. The second objective of this thesis was test whether Callichirus garthi (Retamal, 1975) which is considered as a junior synonymy of C. seilacheri constitute a valid species for the eastern Pacific. For this, a full comparison between specimens of the genus Callichirus collected along the Pacific coast of Central America and Chilean coast, including the type-locality of C. seilacheri and C. garthi was realized. The comparison revealed important morphological differences between both species. For example, in C. garthi the tips of the eyestalk are parallel while diverge distally forming an about 60-70° angle in C. seilacheri. Adult males of both species share unequal chelipeds; however, only C. seilacheri has a hook on ventral margin of ischium and its merus is armed with a rectangular lobe over anterior ventral margin. Additional material collected along the Chilean coast and from different localities from the Pacific coast of Costa Rica allowed confirms the taxonomic status of both species in the Eastern Pacific. All specimens collected along the Chilean coast belong to C. garthi while those of Costa Rica fit to form of C. seilacheri from El Salvador. According to the results, C. garthi is a valid species. Therefore, it is postulated the separation of large population of C. seilacheri into two different populations: (i) one belonging to C. seilacheri which distributes from Mexico to Costa Rica (~19º 08º N), (ii) other assigned to C. garthi which encompasses, at least, between 18º S 37º S of the Chilean coast. The abundant-centre hypothesis (ACH) is based on the assumption that physiological constraints limit populations at the edges of their distributional range. In the third chapter is examined the applicability of the ACH in a marine system by testing whether physiological predictions are reflected in large-scale variations of life-history traits. In order to achieve this information, specimens of Callichirus garthi were collected in the intertidal zone at seven sampling sites. In each site we evaluated (i) local abundance, (ii) maximum body size, (iii) sex-ratio, (iv) length-size frequency distribution, and (v) size at maturity. The main outcomes revealed that C. garthi is a species of low occurrence which was present in seven of all visited beaches (N = 61). Callichirus garthi was clearly less abundant within local populations near the centre and increased towards the northern and southern edges of its distribution. This pattern of abundance was significantly fitted by the abundant edge model. At the southern end and northern of the distribution, population structure was composed by individuals of all sizes in contrast with localities from the centre where individuals were concentrated in a narrow size range. Surprisingly at the edges (north and south), the sex ratio was extremely balanced. Physical variables (SST, grain size) had not influences on variation of life-history traits; however, the local abundance was slightly correlated with the distance between each locality and the closest river and was strongly correlated with population structure. Overall, the observed pattern was intimately linked with input of nutrients from the closest rivers. The findings allow separate the great population of C. garthi along the Chilean coast in two kinds: (A) stable populations (at the border of distribution), and (B) unstable populations (at the centre of distribution). In both cases, the population demography is controlled by dense-dependent factors. The results underline the importance of incorporating ecological, physiological and life-history studies in future tests of the ACH. Generalizations about breeding patterns of near-shore benthic marine invertebrates have proposed that tropical species have continuous reproduction as a reflection of constant temperature throughout the year (Ortons hypothesis). Based on this assumption, it was analysed the reproductive periodicity and egg production in the intertidal ghost shrimp Callichirus seilacheri from the Central Pacific coast of Costa Rica. In order to obtain such information, a total of 449 individuals were collected monthly from December 2011 to November 2012. The results showed that females with ovaries filled with mature oocytes were present throughout the whole year. However, the presence of ovigerous females was restricted to the period between May and November which fits to a seasonal breeding cycle. Apparition of egg-bearing females was statistically correlated with the decrease of salinity detected during rainy season, but not with temperature. Compared to C. garthi from temperate waters, C. seilacheri produced on the average four times less eggs and smaller. Variability in reproductive features and body size of these species seem to reflect physiological constraints imposed by temperature in cold and warm regions. The aspects examined in each chapter of this thesis constitute new antecedents about morphology, taxonomy, and ecology of one of the most representative genus of the family Callianassidae from American coast. Each one of these informations may be considered of especial importance for the management and conservation of the Callichiruss populations from the eastern Pacific. Especially, because both species herein analyzed are frequently collected as bait for commercial and recreational fishing in some small villages along Pacific coast of America.

Deep-water trawling (>200 m deep) for crustaceans in the South West Indian Ocean (SWIO) yields catches of several species, including prawns (Haliporoides triarthrus, Aristaeomorpha foliacea, Aristeus antennatus and Aristeus virilis), langoustine (Metanephrops mozambicus), spiny lobster (Palinurus delagoae) and geryonid crab (Chaceon macphersoni). Infrequent deep-water trawling takes place off Tanzania, Kenya and Madagascar; however, well-established fisheries operate off Mozambique and South Africa. Regular trawling off South Africa started in the 1970’s, mainly targeting M .mozambicus and H. triarthrus. Catch and effort data for the South African fishery were regularly recorded in skipper logbooks over a 23 year period (1988 – 2010); this database was obtained from the Department of Agriculture, Forestry and Fisheries (DAFF) in order to assess abundance trends of M. mozambicus and H. triarthrus. Generalized linear models (GLM) were used to quantify the effects of year, month, depth and vessel on catch per unit effort (CPUE). By year, the standardized CPUE of M. mozambicus increased, and three factors (or a combination of them) could explain the trend: reduced effort saturation, improved gear and technology, or an increase in abundance. By month, CPUE peaked in July and was highest between depths of 300 and 399 m. The standardized CPUE of H. triarthrus fluctuated more by year than for M. mozambicus, possibly because it is a shorter-lived and faster growing species. The monthly CPUE peaked in March, and was highest between depths of 400 and 499 m. Totals of 2 033 M. mozambicus (1 041 males and 992 females) and 5 927 H. triarthrus (2 938 males and 2 989 females) were sampled at sea between December 2010 and March 2012, during quarterly trips on-board a fishing trawler. A GLM framework was used to explore their size composition, sex ratio variability, size at maturity and reproductive cycles. Male and female M. mozambicus size distributions were similar, but varied by month and decreased as depth increased. Female H. triarthrus were significant larger than males; size structure varied by month, but showed no change over depth. The sex ratio of M. mozambicus favoured males (1 : 0.89), but was close to parity in all months, except November when males predominated. H. triarthrus exhibited parity (1 : 1.002) with no significant variations in sex ratios by month. The proportion of egg-bearing M. mozambicus in the population declined between March and August (hatching period) and then increased until December (spawning period). The L₅₀ (length at 50% maturity) of M. mozambicus was estimated to be 49.4 mm carapace length (CL), and the smallest and largest observed egg-bearing females were 33.5 and 68.6 mm, respectively. No reproductively active female H. triarthrus were recorded during the sampling period. Growth parameter estimates for M. mozambicus (male and female combined) using Fabens method were K = 0.48 yearˉ¹ and L∞ = 76.4 mm CL. Estimates for the von Bertalanffy growth formula (VBGF) were: K = 0.45 yearˉ¹ and L∞ = 76.4 mm CL. H. triarthrus male and female growth parameter were estimated separately. For males they were K = 0.5 yearˉ¹ and L∞ = 46.6 mm CL using Fabens method, and K = 0.76 yearˉ¹ and L∞ = 46.6 mm CL using the VBGF. For females they were K = 0.3 yearˉ¹ and L∞ = 62.9 mm CL using Fabens method, and K = 0.47 yearˉ¹ and L∞ = 62.9 mm CL using the VBGF. CL to total weight regressions were calculated for both species; no significant differences were found between male and female M. mozambicus, although H. triarthrus females became larger and heavier than males. Comparisons with three earlier studies (Berry, 1969; Berry et al., 1975; Tomalin et al., 1997) revealed no major changes in the biology of either species off eastern South Africa. Stocks appear to be stable at current levels of fishing pressure, although some factors are not yet fully understood. Disturbance caused by continual trawling over a spatially limited fishing ground may affect distribution and abundance patterns, especially in M. mozambicus, which was less abundant in the depth range trawled most frequently. The absence of reproductive H. triarthrus in samples suggests that they occur elsewhere, and there is some evidence of a possible spawning migration northwards to Mozambique; this suggests that H. triarthrus is a shared stock between South Africa and Mozambique. The results from this thesis will add to the knowledge of M. mozambicus and H. triarthrus in the SWIO, and provide a basis for developing sustainable management strategies for the deep-water crustacean trawl fishery off eastern South Africa. / Thesis (M.Sc.)-University of KwaZulu-Natal, Westville, 2013.