Digital library

  • The Use of Positively Buoyant Ground Cables and Sweep to Reduce Seabed Contact and to Enhance Species Selectivity

    A groundfish net was modified to limit its bottom contact and to improve escapement of bottom-tending fish species. A model was first evaluated in the flume tank facility of Memorial University, followed by field trials. Two trawl configurations were tested against a Control, during fishing experiments in 2007 and 2008. In the first configuration, the goal was to fish the net approximately 1.5' off the seabed, to retain cod and haddock while reducing catches of flounders and other demersal species. In the second rig, the Experimental trawl was fished up to 3' off the seabed, to retain haddock while reducing catches of cod, flounders and other demersal species.

    Flume tank tests indicated that a stable condition and proper fishing heights were achieved with a combination of floats on the headrope, footrope and ground gear, combined with weights attached to the wing ends. Field trials followed the recommendations developed in the laboratory, and video observation revealed a stable fishing condition, with little contact with the seabed. Catch information was hampered by low fish availability, but indicated that the correct escapement pattern was occurring, with the exception of higher-than-desired escapement of haddock during the second experiment. 

    Author(s): Lynn Wardwell, Dana L. Morse

  • The underexplored potential of green macroalgae in aquaculture

    Green macroalgae (Chlorophyta) currently represent a residual fraction (<1%) of global seaweed biomass production landings. In turn, red (Rhodophyta) and brown (Ochrophyta) macroalgae dominate the remaining percentage of aquaculture production, exceeding 32 million tonnes per annum. However, the industry relies on a relatively low number of species, in which as few as seven macroalgal genera collectively represent the bulk of global production metrics. At present, innovation and increased sustainability of the industry calls for diversification of macroalgal species/strains in aquaculture to counteract potential adverse effects ensuing from genetic impoverishment, decreased resilience to disease and climate change. Despite the dominance of red and brown seaweed regarding production figures, aquaculture of green macroalgae has witnessed an increasing trend in productivity and diversification over the last decades, particularly in Asia, where green seaweed taxa often occupy specific market niches in the food sector. Furthermore, growing interest in green seaweeds in aquaculture has been highlighted for different applications in emerging western markets (eg IMTA, biorefineries, food delicacies), owing to a unique diversity of cytomorphologies, ecophysiological traits, propagation capacities and bioactive compounds featured by this group of macroalgae. Cultivation technologies are relatively well developed, but sustainability assessments are scarce and required to unlock the potential of green seaweeds. Although it is likely that green macroalgae will remain occupying specialised market niches, in which high-value products are favoured, we argue that aquaculture of chlorophytan taxa presents itself as a compelling option under the current quest for commercial diversification of products and expansion of the sector.

    Author(s): Anthony Moreira, Sónia Cruz, Rúben Marques, Paulo Cartaxana

  • The Thecal Structure of a Marine Toxic Dinoflagellate Gambierdiscus toxicus gen. et sp. nov. Collected in a Ciguatera-endemic Area

    Gambierdiscus toxicus gen. et sp. nov. is described. This is a toxin producing dinoflagellate which was collected in a ciguatera-endemic area. Observations were made using both a light microscope with or without phase-contrast and a scanning electron microscope. This species is distincdve in its antero-posterior compressed body shape, with a circular narrow deep cingulum and a deep hollow sulcus. The theca consists of 33 plates: Po, 3', Oa, 7", 6c, 8s, 6"', 1p, 1"". The plate pattern of this species is characteristic in having extremely reduced precingulars 1" and 7", which are situated between apical 1' and the sulcal excavation and are clearly separate from apical 2" and 4". These features and others indicate that this genus should be assigned to the Heteraulacaceae family. This species is always sessile and attaches to dead coral and seaweed, especially brown alga, Turbinaria ornata J. AGARDH. A large number of this species were taken around the Gambier Islands, French Polynesia, in May 1975.

    Author(s): Rokuro Adachi, Yasuwo Fukuyo

  • The system of galactans of the red seaweed, Kappaphycus alvarezii , with emphasis on its minor constituents

    The galactans extracted with hot water from Kappaphycus alvarezii, after previous extraction at room temperature, are mainly composed of j-carrageenans (~74%) and l-carrageenans (~3%). However, a significant percentage of these galactans (at least 14%) is composed of sulfated agarans and, possibly, agaran-type sulfated DL-hybrid galactans. These agarans are partially substituted on C-2 or C-4 or disubstituted on both positions of the b-D-galactose units and on C-3 or C-2 and C-3 of the a-L-galactose residues with sulfate groups or single stubs of b-D-xylopyranose, D-glucopyranose, and galactose or with D-glucopyranosyl-(1!4)- D-glucopyranose side chains. Significant quantities of 2-O-methyl- and 3-O-methyl-L-galactose units are also present. A great tendency to retain Ca2+ and Mg2+, in spite of massive treatments with Na+ and K+ salts, was observed. The complexation between agarans and agarans–j-carrageenans through divalent cations and the possible zipper-type carbohydrate–carbohydrate interactions would be two complementary mechanisms of interactions.

    Author(s): Alberto S. Cerezo, Marina Ciancia, José M. Estevez

  • The status of mariculture in northern China

    The People’s Republic of China has a long history of mariculture production. The mariculture industry in China has achieved breakthroughs in the hatchery, nursery and culture techniques of shrimp, molluscs and fish of high commercial value since the 1950s.

    The first major development was seaweed culture during the 1950s, made possible by breakthroughs in breeding technology. By the end of the 1970s, annual seaweed production had reached 250 000 tonnes in dry weight (approximately 1.5 million tonnes of fresh seaweed). Shrimp culture developed during the 1980s because of advances in hatchery technology and economic reform policies. Annual shrimp production reached 210 000 tonnes in 1992. Disease outbreaks since 1993, however, have reduced shrimp production by about two-thirds. Mariculture production increased steadily between 1954 and 1985, but has been growing exponentially since 1986, mostly driven by mollusc culture. Mollusc culture in China began to expand beyond the four traditional species (oyster, cockle, razor clam and ruditapes clam) in the 1970s. Mussel culture was the first new industry to emerge, followed by scallop aquaculture in the 1980s. Abalone culture has become a major industry in the 1990s. Traditional oyster and clam culture has also advanced and expanded in recent years. Now more than 30 species of marine molluscs are cultured commercially in China. Because of the rapid development in recent years, mollusc culture has become the largest sector of the Chinese mariculture industry, accounting for 81 percent of the total production by weight.

    Therefore, the industrialization level and culture techniques for the major species in China have reached an advanced international level, with some leading the world aquaculture sector. China is also the largest country in mariculture.

    Marine aquaculture has grown rapidly over the last decade. Marine cultivable areas in China, which include shallow seas, mudflats and bays, are estimated to occupy more than 1.33 million ha, as most marine plants and animals can be cultivated within the 10 m isobath using current culture technologies. In 2002 the area under cultivation and the output reached 1 352 000 ha and 12.1 million tonnes, respectively.

    The principal species cultured in northern China are listed in Table 1. 

    Author(s): Chen Jiaxin, Chang Yaqing

  • The Status of Kelp Exploitation and Marine Agronomy, with Emphasis on Macrocystis pyrifera, in Chile

    Kelp cultivation started in Japan, China and Korea, mainly for human consumption; new applications are still expanding. In Chile, three "wild" Lessonia species and Macrocystis pyrifera are under a strong and increasing pressure of exploitation mainly for alginate production and as a source of feed for abalone. Regulatory restrictions for kelp exploitation and the increased demand for biomass provided a positive environment for the installation of a kelp farming industry. Pilot-production studies demonstrated that 200 tonnes (fresh)/ha/year can be achieved and genetic diversity and breeding studies suggested that this volume could be increased. Kelp disease research is a necessary condition for securing the future development of this industry, as are environmental studies on the impacts of large-scale aquaculture. Beyond the positive bioremediation, ecosystem service effects that kelp farming can provide, especially in a region such as in southern Chile, where intensive salmon and mussel cultivation occurs. Life Cycle Assessment suggests that the energy returns on investment in kelp farming are positive, but more detailed data are still required.

    Author(s): Alejandro H. Buschmann, Steven Prescott, Philippe Potin, Sylvain Faugeron, Julio A. Vásquez, Carolina Camus, Javier Infante, María Carmen Hernández-González, Alfonso Gutíerrez, Daniel A. Varela

  • The State of World Fisheries and Aquaculture 2012

    In addition to striving to meet the United Nations Millennium Development Goals, the global community is also grappling with other pressing and complex challenges such as the widespread economic crisis and the effects of climate change. It is in this context that this edition of The State of World Fisheries and Aquaculture highlights the vital role of fisheries and aquaculture in both food and nutrition security as well as economic expansion.

    The sector remains a major supplier of high-quality animal protein and supports the livelihoods and well-being of more than ten percent of the world’s population. International trade in fish has reached new peaks as overall production has continued to rise. Yet, as the document underlines, an array of problems – ranging from the need for more effective governance to that of ensuring environmental sustainability – threatens to undermine the sector’s valuable contribution to alleviating hunger and reducing poverty.

    Using the latest available statistics on fisheries and aquaculture, this edition presents a global analysis of the sector’s status and trends. It also examines broader related issues such as gender, emergency preparedness and the ecosystem approach to fisheries and aquaculture. Selected highlights, from ecolabelling and certification to the effects of fisheries management policies on fishing safety, provide insights on specific topics. Finally, the document looks at the opportunities and difficulties for capture fisheries in the coming decades.

    Author(s):

  • The State of Food and Agriculture

    Recent food crises and growing concerns about global climate change have placed agriculture on top of the international agenda. governments, international organizations, and civil society groups gathered at the group of eight (g8), the group of twenty finance Ministers and central bank governors (g20) and rio+20 summits in 2012 have recognized a convergence between the dual goals of eradicating hunger and making agriculture sustainable. achieving these goals will require a significant increase in agricultural investment but, more importantly, it will require improving the quality of this investment. 

    Author(s):

  • The Seeding and Cultivation of a Tropical Species of Filamentous Ulva for Algal Biomass Production

    Filamentous species of Ulva are ideal for cultivation because they are robust with high growth rates and maintained across a broad range of environments. Temperate species of filamentous Ulva are commercially cultivated on nets which can be artificially ‘seeded’ under controlled conditions allowing for a high level of control over seeding density and consequently biomass production. This study quantified for the first time the seeding and culture cycle of a tropical species of filamentous Ulva (Ulva sp. 3) and identified seeding density and nursery period as key factors affecting growth and biomass yield. A seeding density of 621,000 swarmers m-1 rope in combination with a nursery period of five days resulted in the highest growth rate and correspondingly the highest biomass yield. A nursery period of five days was optimal with up to six times the biomass yield compared to ropes under either shorter or longer nursery periods. These combined parameters of seeding density and nursery period resulted in a specific growth rate of more than 65% day21 between 7 and 10 days of outdoor cultivation post-nursery. This was followed by a decrease in growth through to 25 days. This study also demonstrated that the timing of harvest is critical as the maximum biomass yield of 23.068.8 g dry weight m21 (228.76115.4 g fresh weight m21 ) was achieved after 13 days of outdoor cultivation whereas biomass degraded to 15.567.3 g dry weight m21 (120.2671.8 g fresh weight m21 ) over a longer outdoor cultivation period of 25 days. Artificially seeded ropes of Ulva with high biomass yields over short culture cycles may therefore be an alternative to unattached cultivation in integrated pond-based aquaculture systems.

    Author(s): Christina Carl, Rocky de Nys, Nicholas A. Paul

  • THE SEAWEED RESOURCES OF EASTERN CANADA

    Canada occupies a special place among the world producers of seaweeds, mostly because it ranked first, from approximately 1950 to 1970, as a producer of the red alga Chondrus crispus (Irish moss), historically the first source of raw material for carrageenan extraction. However, seaweed harvesting along the coasts of the Maritimes is not a long-standing tradition, except in the case of Palmaria palmata (dulse), which has been harvested along the Bay of Fundy (especially on Grand Manan Island) for more than a century (even if the start of this cottage industry is difficult to date precisely). This chapter will focus on the seaweed industry on the Atlantic (East) Coast of Canada, the Pacific (West) Coast industry being treated in a separate chapter by S. Lindstrom. Along the East Coast, the emphasis will be on the Maritimes, which include the provinces of Prince Edward Island (PEI), Nova Scotia (NS) and New Brunswick (NB) (Fig. 1). The two provinces of Québec, and Newfoundland and Labrador are omitted, even though they have been the subject of numerous surveys, exploratory missions and reports, because no significant industry is presently operating there, except the sporadic harvesting of Laminaria sp. (kelp) in Québec (along the St. Lawrence Estuary and the Baie des Chaleurs) which was estimated at 500 wet tons (WT) in 1994 (Bodiguel 1995), and the harvesting of Ascophyllum nodosum (rockweed) and Laminaria sp. by a few small companies in Newfoundland.

    Author(s): RAUL UGARTE, THIERRY CHOPIN

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