Academic literature on the topic 'Marine resources, kelp, crabs'

Abstract Lakes, rivers and oceans provide unique resources and support fisheries and aquaculture worldwide. The fisheries and aquaculture sector of Kenya contributes approximately 0.8% to the country’s GDP. Marine production is about 9 000 tonnes per year. Marine finfish form the bulk of the marine production, while shellfish (e.g. prawns, lobsters and crabs), molluscs (e.g. octopi and squids) are underexploited. The Fishery sector has the potential of about USD 5 billion for the Blue Economy in Kenya. Crab fishery in Kenya is active in some areas of the south and north coast. The crab resources along the Kenyan waters are diverse and a variety of species are edible. The most commonly fished crab by artisanal fishers is the Mangrove Mud Crab Scylla serrata. Semi-commercial and industrial fishers usually have portunid and other deep sea crabs as by-catch in trawl and longline fisheries, which in many cases are unutilized. Exports of live crabs have increased over the years, with exports mainly to Asian countries. Export of frozen crabs started recently. The need to sustainably utilize lake, river and ocean resources is recognized and important in promoting Blue Economy. Sustainable development of crab fishery provides a potential area for the Blue Economy development in Kenya. Research is essential to crab fishery development.

Kelp forests are phyletically diverse, structurally complex and highly productive components of coldwater rocky marine coastlines. This paper reviews the conditions in which kelp forests develop globally and where, why and at what rate they become deforested. The ecology and long archaeological history of kelp forests are examined through case studies from southern California, the Aleutian Islands and the western North Atlantic, well-studied locations that represent the widest possible range in kelp forest biodiversity. Global distribution of kelp forests is physiologically constrained by light at high latitudes and by nutrients, warm temperatures and other macrophytes at low latitudes. Within mid-latitude belts (roughly 40–60° latitude in both hemispheres) well-developed kelp forests are most threatened by herbivory, usually from sea urchins. Overfishing and extirpation of highly valued vertebrate apex predators often triggered herbivore population increases, leading to widespread kelp deforestation. Such deforestations have the most profound and lasting impacts on species-depauperate systems, such as those in Alaska and the western North Atlantic. Globally urchin-induced deforestation has been increasing over the past 2–3 decades. Continued fishing down of coastal food webs has resulted in shifting harvesting targets from apex predators to their invertebrate prey, including kelp-grazing herbivores. The recent global expansion of sea urchin harvesting has led to the widespread extirpation of this herbivore, and kelp forests have returned in some locations but, for the first time, these forests are devoid of vertebrate apex predators. In the western North Atlantic, large predatory crabs have recently filled this void and they have become the new apex predator in this system. Similar shifts from fish- to crab-dominance may have occurred in coastal zones of the United Kingdom and Japan, where large predatory finfish were extirpated long ago. Three North American case studies of kelp forests were examined to determine their long history with humans and project the status of future kelp forests to the year 2025. Fishing impacts on kelp forest systems have been both profound and much longer in duration than previously thought. Archaeological data suggest that coastal peoples exploited kelp forest organisms for thousands of years, occasionally resulting in localized losses of apex predators, outbreaks of sea urchin populations and probably small-scale deforestation. Over the past two centuries, commercial exploitation for export led to the extirpation of sea urchin predators, such as the sea otter in the North Pacific and predatory fishes like the cod in the North Atlantic. The large-scale removal of predators for export markets increased sea urchin abundances and promoted the decline of kelp forests over vast areas. Despite southern California having one of the longest known associations with coastal kelp forests, widespread deforestation is rare. It is possible that functional redundancies among predators and herbivores make this most diverse system most stable. Such biodiverse kelp forests may also resist invasion from non-native species. In the species-depauperate western North Atlantic, introduced algal competitors carpet the benthos and threaten future kelp dominance. There, other non-native herbivores and predators have become established and dominant components of this system. Climate changes have had measurable impacts on kelp forest ecosystems and efforts to control the emission of greenhouse gasses should be a global priority. However, overfishing appears to be the greatest manageable threat to kelp forest ecosystems over the 2025 time horizon. Management should focus on minimizing fishing impacts and restoring populations of functionally important species in these systems.

This study compares density and size structure of kelp Lessonia berteroana and sea urchins Loxechinus albus inside and outside a port concession area in Caldera. Greater abundance and larger adult individuals in populations of both benthic resources in this zone preliminarily indicates that this might be replicating a marine protected area. In the future, this port concession could contribute to the conservation of benthic resources as a reference site, without access to fisheries, useful for validating or implementing measures and actions in management plans or other instruments to support conservation.

Abstract Alaska has the longest coastline of all of the states in the USA. This coastal zone stretches from the temperate zone to past the Arctic circle. Oceanographic conditions vary from quiet estuaries to exposed open coasts. Water temperatures range from over 20°C in the summer in the south to ice covered water in the north. Consequently, the marine flora is plentiful and diverse with over 500 species of seaweeds. Three species of floating kelps occur from the southern boundary to Kodiak Island and westward along the Aleutian Chain. Species of Fucus are dominant in the intertidal along most of the coastline. There is also an abundance of red algae in the intertidal and subtidal. There is only minimal subsistence and commercial utilization of the seaweed resource. The major commercial use of seaweeds is in the herring spawn-on-kelp fishery. “Black seaweed” (Pyropia sp.) is a special resource for Alaskan Native subsistence harvest. Recently, there has been increasing interest and activity in the commercial mariculture of kelps such as Saccharina latissima and Alaria marginata.

The mangrove forest are natural and renewable. resources Mangrove has the physical, chemicaland biological function which highly support the fulfillment of human needs and serve as a bufferbalance of the ecosystem in coastal areas. One of the functions associated with the mangrovebiological existence as a source of diversity of marine life. Marine life is affected by the presenceof mangrove forests among mangrove crab (Scylla serrata) to maintain the ecological balance andcause the energy cycle running fast. This study aims to determine the condition of environmentalfactors, the relative fitness and spatial distribution of mangrove crabin the mangrove forests BlockBedul Kali Segoro Alas Purwo National Park. Data from the study are described and classified bysimilarity of environmental factors, then performed multiple linear regression betweenenvironmental factors with relative fitness and spatial distribution of mangrove crabs. The resultsshowed that the average relative fitness mangrove crabs at all the research station is 69 with astandard deviation of 13.51. Spatial distribution of mangrove crab at any observation station isless than 1, so it can be concluded that the distribution is uniform. Environmental factors withrelative fitness mud crab significant correlation, but no significant correlation betweenenvironmental factors with the spatial distribution of mangrove crabs. Keywords: Relative Fitnes Crab Mangrove, Mangrove Crab Spatial Distribution, Alas Purwo National Park

SynopsisMarine resources, including seaweeds, have always played an important role in the history of the Orkney Islands, particularly over the period of the ‘kelp’ industry between 1719 and the 1930s. Recent studies confirm the presence of major sub-tidal seaweed forests dominated by the brown seaweed Laminaria hyperborea.In this paper, consideration is given to the possible revitalisation of the seaweed industry in Orkney, involving major developments of both harvesting and processing technology. This is seen as a logical component of an integrated inshore marine resource management strategy for the Islands.

Se analizan las vedas vigentes para regular el aprovechamiento y conservación de los recursos pesqueros dulceacuícolas, marinos y estuarinos de Colombia. En los recursos continentales se incluyen peces de las cuencas hidrográficas de los ríos Magdalena, Cauca, San Jorge, Sinú, Orinoco y Amazonas, y algunos embalses y parques nacionales naturales. Los recursos estuarinos y marinos incluyen los litorales del Mar Caribe y del Océano Pacífico, con normas para corales, moluscos, cangrejos, peces, tortugas y delfines.This article analyses the current closed seasons aiming at regulating the use and conservation of the fresh, marine and estuarine fishing resources of the hydrographic basins of Colombia. The continental resources include the hydrographic basins of the rivers Magdalena, Cauca, San Jorge, Sinú. Orinoco and Amazonas; some reservoirs and some National Parks. Estuarine and marine resources include the Caribbean Sea and Pacific Ocean with standards for corals, mollusks, crabs, fish, turtles and dolphins.

Abstract Growth is a key attribute influencing population dynamics and fishery production, and understanding factors that affect the growth of individuals in a population is essential in fisheries science and management. This study analyses 18 years of fishery-independent trawl data to determine the relationships among temperature, density, primary productivity and growth of the blue swimmer crab, Portunus armatus, in a temperate marine embayment. Growth was modelled using mixture distribution analyses and cohort-specific seasonal growth curves to estimate the size of crabs at the age of 0.5 and 1.5 years. Growth was highly seasonal, with size-at-age increasing during the austral summer periods and slowing/ceasing during the cooler winter months. The results from the mixture models were used to estimate the mean size of the 0.5- and 1.5-year-old crabs in each year. Linear models showed that the mean size of adult P. armatus at 1.5 years was negatively related to the density of juvenile (0.5 year) crabs in the previous year (i.e. the same cohort) and chlorophyll a concentrations in this year. Increased chlorophyll a levels may increase the survival of larval and megalopal P. armatus, leading to density-dependent effects such as increased competition among juveniles for food and spatial resources, and ultimately, reduced growth.

Australia has 12 major drainage basins, but most water use and extraction comes from the Murray- Darling Basin, despite not having Australia?s more populous cities. About 66% of surface water use in Australia is extracted from the rivers of the Murray-Darling Basin (NLWRA 2001). The ecological impacts are widespread and insurmountable: key ecosystems are in various stages of collapse. Many of these are conservation reserves and wetlands recognized for their international importance under the Ramsar Convention. Populations of native fish species are considered to be only at 10% of pre European levels with 46% of the 35 fish species now listed as threatened at state level (MDBC 2004). Waterbird populations are also declining significantly, sometimes up to 80% over a period of about 25 years (Kingsford and Thomas 2004; Nebel et al. 2008). Many communities of floodplain vegetation are also in decline. The River Murray no longer breaks through the sand barriers to naturally flow out to sea, with flow now only maintained by a dredge (costing ~$100,000 per week) to ensure that sand does not completely block the Murray mouth. The lower lakes are below sea level for the first time in more than 7,000 years and marine incursions into this freshwater ecosystem have allowed colonies of marine worms Ficopomatus enigmaticus to build their calcareous colonies on the backs of freshwater turtles and crabs weighing them down.

The papers presented in this thesis represent my contributions to the empirical study of marine biological resources. This research has adopted the same experimental approach to: (i) develop scientifically validated techniques to solve specific problems; (ii) use these techniques to detect patterns and form conceptual models about the processes that may have caused them; (iii) do manipulative field experiments to support or refute hypotheses derived from these models; (iv) use these results to develop new models and hypotheses and to test them in new experiments; and (v) recommend, where appropriate, changes to the management of the resources examined. A rigorous, empirical approach is the common feature throughout my research (in its overall direction and subject-to-subject execution) and represents one of the few attempts to adopt such an approach across the three fields in which I have worked: (1) the ecology of underwater kelp systems; (2) the biology of and fishery for a commercially exploited crab; and (3) solving by-catch problems in commercial trawl fisheries.

<em>Abstract</em>.—The Wheeler North Reef (WNR) is a large (70.4 ha [174 acre]) artificial reef in Southern California designed to mitigate the loss of kelp forest habitat and its associated community of algae, invertebrates, and fishes caused by the operation of the San Onofre Nuclear Generating Station (SONGS). Conditions of the SONGS’ operating permit require that the success of WNR in compensating for the kelp forest resources destroyed by the 30 years of the power plant’s operations be determined by long-term monitoring that is independent of the owners of SONGS. Performance standards pertaining to physical and ecological attributes of WNR are used as a basis for determining the success of WNR in meeting the mitigation objective to replace kelp forest resources in kind. We discuss details of the sampling design, evaluation criteria, and monitoring results and show how they are used to inform adaptive management that helps to ensure that the mitigation goals are met.

Marine ornamental decapods are among the most popular invertebrates traded in the global marine aquarium industry. With the exception of the Dendrobranchiata, nearly all other major groups of decapods have at least one species traded as ornamental, the majority being caridean and stenopodidean shrimp, as well as hermit and brachyuran crabs. Found and collected in the wild from tropical coral reefs and coastal lagoons, the aquaculture of marine ornamental decapods is yet to achieve a scale that alleviates the fishing pressure affecting natural populations. Most cultivation efforts have targeted cleaner and boxing shrimp within the genera Lysmata and Stenopus, respectively. While these species are some of the most highly traded, research on their captive culture has been mainly driven by their market value rather than conservation purposes. This is likely the reason why the aquaculture of other species that are also heavily collected, such as hermit and brachyuran crabs, is yet to properly be addressed. This chapter provides an overview of the most emblematic marine ornamental decapod species currently traded for marine aquaria, including their distinctive features, as well as their collection, packing, and shipping techniques. The state of the art of marine ornamental decapod aquaculture is critically revised, with an emphasis on broodstock husbandry and maturation, larviculture, and grow-out to commercial size. Commonly employed systems for stocking breeding pairs, raising larvae, or growing juveniles are detailed, underscoring recirculated systems operating with synthetic seawater due to their potential use in coastal or inland facilities. The main bottlenecks impairing the successful breeding of these organisms are critically addressed, namely the lack of maturation diets customized to secure the nutritional needs of target species, which consequently impairs the production of high-quality larvae for cultivation. The main constraints for larviculture are also highlighted, with special emphasis on the lack of suitable live prey and the ability of several decapod species to delay metamorphosis under suboptimal larval diets. Issues on grow-out, such as poor growth performances and cannibalism, are discussed from a commercial perspective, as well as mitigation actions (e.g., use of live prey and complex shelters). There is a strong need for science-based conservation policies, where accurate data reporting and traceability along the supply chain must be implemented to promote a sustainable use of these resources. Though pricey and popular, marine ornamental decapods are no longer poorly studied when compared to a few years ago. Nonetheless, some key issues still need the attention of researchers, commercial breeders and hobbyists to ensure that these remarkable organisms can continue to be admired in the wild and in aquarium displays.

<em>Abstract</em> — The increasing concern about impacts of bottom trawling, scallop dredging, and other mobile fishing methods has focused primarily on effects on commercial fisheries, but these fishing activities also act more broadly on benthic biological diversity. Because the seabed is erroneously envisioned as a featureless, nearly lifeless plain, impacts of commercial fishing gear have long been underestimated. Structures on and in the seabed, including biogenic structures (reef corals, kelp holdfasts, shells, tubes, and tunnels), create a diversity of habitat patches. They provide refuges from predation and feeding places for demersal fishes and other species. Benthic structural complexity is positively correlated with species diversity and postsettlement survivorship of some commercial fishes. Mobile fishing gear disturbs the seabed, damaging benthic structures and harming structure-associated species, including commercially important fishes, although some other commercial fish species can persist where seabed structures have been removed. Bottom trawling is therefore similar to forest clear-cutting, but it is far more extensive and is converting very large areas of formerly structurally complex, biologically diverse seabed into the marine equivalent of low-diversity cattle pasture. In contrast with the U.S. National Forest Management Act, which governs use of living resources in federally owned forestlands, the 1996 Magnuson-Stevens Fishery Conservation and Management Act does not prevent ecosystem “type conversion” and ignores the need to maintain biological diversity. Preventing further loss of marine biodiversity and key fisheries will depend on our willingness to protect marine areas from effects of mobile fishing methods.

<em>Abstract</em> — The increasing concern about impacts of bottom trawling, scallop dredging, and other mobile fishing methods has focused primarily on effects on commercial fisheries, but these fishing activities also act more broadly on benthic biological diversity. Because the seabed is erroneously envisioned as a featureless, nearly lifeless plain, impacts of commercial fishing gear have long been underestimated. Structures on and in the seabed, including biogenic structures (reef corals, kelp holdfasts, shells, tubes, and tunnels), create a diversity of habitat patches. They provide refuges from predation and feeding places for demersal fishes and other species. Benthic structural complexity is positively correlated with species diversity and postsettlement survivorship of some commercial fishes. Mobile fishing gear disturbs the seabed, damaging benthic structures and harming structure-associated species, including commercially important fishes, although some other commercial fish species can persist where seabed structures have been removed. Bottom trawling is therefore similar to forest clear-cutting, but it is far more extensive and is converting very large areas of formerly structurally complex, biologically diverse seabed into the marine equivalent of low-diversity cattle pasture. In contrast with the U.S. National Forest Management Act, which governs use of living resources in federally owned forestlands, the 1996 Magnuson-Stevens Fishery Conservation and Management Act does not prevent ecosystem “type conversion” and ignores the need to maintain biological diversity. Preventing further loss of marine biodiversity and key fisheries will depend on our willingness to protect marine areas from effects of mobile fishing methods.