20 research outputs found
The global integrated world ocean assessment: linking observations to science and policy across multiple scales
In 2004, the United Nations (UN) General Assembly approved a Regular Process to report on the environmental, economic and social aspects of the world's ocean. The Regular Process for Global Reporting and Assessment of the State of the Marine Environment, including Socioeconomic Aspects produced the first global integrated assessment of the marine environment in December 2016 (known as the first World Ocean Assessment). The second assessment, to be delivered in December 2020, will build on the baselines included in the first assessment, with a focus on establishing trends in the marine environment with relevance to global reporting needs such as those associated with the UN Sustainable Development Goals. Central to the assessment process and its outputs are two components. First, is the utilization of ocean observation and monitoring outputs and research to temporally assess physical, chemical, biological, social, economic and cultural components of coastal and marine environments to establish their current state, impacts currently affecting coastal and marine environments, responses to those impacts and associated ongoing trends. Second, is the knowledge brokering of ocean observations and associated research to provide key information that can be utilized and applied to address management and policy needs at local, regional and global scales. Through identifying both knowledge gaps and capacity needs, the assessment process also provides direction to policy makers for the future development and deployment of sustained observation systems that are required for enhancing knowledge and supporting national aspirations associated with the sustainable development of coastal and marine ecosystems. Input from the ocean observation community, managers and policy makers is critical for ensuring that the vital information required for supporting the science policy interface objectives of the Regular Process is included in the assessment. This community white paper discusses developments in linking ocean observations and science with policy achieved as part of the assessment process, and those required for providing strategic linkages into the future.Agência financiadora - United Nations Division for Ocean Affairs and the Law of the Seainfo:eu-repo/semantics/publishedVersio
Experimental evaluation of influence of FADs on community structure and fisheries in coastal Kenya
Fish aggregating devices (FADs) have been widely used by commercial fisheries to increase the catchability of pelagic stocks in the open sea. FADs have the potential to enhance nearshore small-scale fisheries where stocks are often overfished. This study examined changes in catch composition, abundance, catch and effort, and aspects of diversity in Kenya's nearshore coastal fisheries after deployment of anchored fish aggregating devices (AFADs). The study combined both fishery independent and dependent methods in assessing changes in fish assemblages post-deployment. Results showed orders of magnitude increase in length, weight, commercial value, and catch per unit effort (CPUE) of landed catch after deployment of FADs suggesting that FADs had a positive effect on the local fishery. Species richness at FAD sites increased post-deployment (n = 281) compared to pre-deployment values (n = 223). Simultaneous use of several complementary structural indices may be required in order to accurately describe and monitor fish assemblages around the FADs. The findings suggest that AFADs are capable of creating both short and long-term impacts on livelihoods, with the potential to deflect pressure on the overfished nearshore fish stocks. However, more research will be needed on redistribution of fish around FADs, design and placement configuration, and site selection amongst others
Semi-terrestrial crabs in mangrove habitat: spatial distribution and their reproductive pattern on an East African coast
Dottorato di ricerca in biologia animale (etologia). 11. ciclo. A.a 1996-99. Tutore Marco Vannini. Coordinatore Stefano TurillazziConsiglio Nazionale delle Ricerche - Biblioteca Centrale - P.le Aldo Moro, 7, Rome; Biblioteca Nazionale Centrale - Piazza Cavalleggeri, 1, Florence / CNR - Consiglio Nazionale delle RichercheSIGLEITItal
Patterns of spat settlement recorded for the tropical oyster crassostrea cucullata (born 1778) and the barnacle, balanus amphitrite (darwin 1854) in a mangrove creek
The spatfall patterns of the oyster, Crassostrea cucullata (Born 1778) and the barnacle, Balanus amphitrite (Darwin 1854) on cemented coconut shells were studied in relation to shore levels and monsoon seasons in East Africa. Both oysters and barnacles settled most frequently above the Mean Tide Level (MTL). About 75.6% of the oyster and 96.9% of the barnacles occurred above the MTL. Thus below MTL, the oyster spat had a better niche advantage over the barnacles. However, at the latter levels the oysters faced heavy competition from fouling organisms, which were mostly spirobids, serpulids, bryozoans, hydrozoans and sponges. The spat of both oysters and barnacles showed seasonality in their settlement. About 93.1% of the total oyster spat settlement occurred in the South East Monsoon (SEM) and the number of spat at peak settlement was 12.6 times the total spat settlement in the North East Monsoon (NEM). As regards the barnacles, 86.4% of the total barnacle spat settlement occurred in SEM and the number of spat in the peak settlement was 3.4 times the total settlement in NEM. Oysters and barnacles on the cemented coconut shells had a wider vertical distributional range than those found on mangrove trees. © 1994 Taylor & Francis Group, LLC.SCOPUS: ar.jinfo:eu-repo/semantics/publishe
Homing experiments in the tree-climbing crab Sesarma leptosoma (decapoda, grapsidae)
Sesama leptosoma an East African mangrove-dwelling crab, migrates twice a day from a system of known dens among the roots to well-defined feeding areas in the branches of trees, reaching 15 m high. Field experiments were performed to test whether chemical or visual cues are involved in the orientation and homing of this species to reach their feeding areas. Manipulation of the substratum at branch junctions, in order to alter possible chemical cues, did not affect homing ability in S. leptosoma. Moreover, crabs trained to cross an asymmetrical artificial wooden fork could still follow their preferred directions after (1) the fork branches had been switched, (2) the whole fork had been rotated around the trunk, resulting in a right-left inversion, and (3) the inversion of two wide black and white screens hiding most of the canopy from view of the climbing crabs. These results suggest that S. leptosoma may not rely on reference systems such as chemical trail-following and chemical or visual cues from the substratum, but probably depend on complex visual information from the surroundings trunks and/or from the sun's position integrated with junction sequence memory.Link_to_subscribed_fulltex
Predatory activity and spatial strategies of Epixanthus dentatus (Decapoda: Oziidae), an ambush predator among the mangroves
The predatory patterns and spatial strategies of Epixanthus dentatus were studied in a mangrove creek on the Kenyan coast, together with laboratory analysis aimed at assessing the natural diet. This xanthoid fed on almost all the slowly moving invertebrates common in the forest and actively preyed at night, using an ambush technique. Epixanthus dentatus is faithful to individual dens among the roots and to well-defined feeding areas within a 3-m radius, which they shared with an average of 2 other individuals. The high density of E. dentatus seemed to affect the behavior of major prey species; various grapsid crab species reduced their climbing activity during the peak activity periods of E. dentatus. The density of E. dentatus among the mangrove roots was determined both by the number of suitable dens, and, more directly, by the density of prey species.Link_to_subscribed_fulltex
Influence of Seasonality and Bathymetry on Assemblage Structure of Decapod Crustaceans in the Malindi-Ungwana Bay, Kenya
Decapod crustaceans support both artisanal and semi-industrial fisheries in the Western Indian Ocean (WIO) region. Despite their commercial value, data on assemblage structure is lacking in most of the WIO region but are important for stock management. This study provides information on seasonal and bathymetric variation in assemblage structure of decapod crustaceans in Malindi-Ungwana Bay, a biodiversity rich ecosystem in Kenya. Samples were collected during the northeast monsoon (NEM) and southeast monsoon (SEM) seasons during a two-week experimental bottom trawling survey in 2011 under the South West Indian Ocean Fisheries Project (SWIOFP). A total of 43 transects covering an estimated area of 546 nm2 were trawled in four depth zones (0-10, 10-20, 20-40 and 40-100 m) for both seasons. Twenty species of decapod crustaceans belonging to 7 families were sampled in both seasons. The species were distributed in the families; Penaeidae, Portunidae, Calappidae, Majidae, Matutidae, Palinuridae and Scyllaridae. The penaeid shrimps had higher relative numerical abundance both in the NEM (89.3%) and SEM (85.3%) seasons. Of the penaeid shrimps, Fenneropenaeus indicus, had the highest relative abundance both in the NEM (58%) and SEM (42%) season. ANOSIM test indicated significant difference in total crustacean abundance (individuals/km2) between the depth zones (R=0.375; P=0.001; considering all seasons) but no significant difference between the seasons (R= -0.031; P=0.602; considering all depths). Simple Correspondence Analyses segregated the population into SEM assemblages dominated by the Penaeidae and a mixed group NEM assemblage. Canonical Correspondence Analysis showed temperature, salinity, Secchi depth and dissolved oxygen to have seasonal influence on the bathymetric distribution of the crustaceans in the bay. The structure of the assemblages seems to be influenced more by depth profiles than by seasonality. It is recommended that variations in bathymetric distribution of the crustaceans be taken into consideration when developing a crustacean fishery management plan for the bay.
Growth and survival of post-larval giant tiger shrimp Penaeus monodon feeding on mangrove leaf litter biofilms
Biofilm associated with decomposing mangrove leaf litter is a food source for shrimp post-larvae (PL). PL of giant tiger shrimp Penaeus monodon foraging on leaf litter of Rhizophora mucronata with developing biofilm at 1, 3, 4, 6, and 8 wk of decomposition were tested for specific growth rate (SGR, %) and percentage survival (SR, %). Biofilm was analyzed for species composition, abundance, and biomass of microalgae and epifauna. Microalgal biomass increased with the progress of litter decomposition. Diatoms, especially Navicula sp. and Nitzschia sp., dominated the first 6 wk of litter decomposition with a percentage cover of 88 and 99% during the third and fourth weeks, respectively. Cyanobacteria dominated in the 8 wk old biofilm with 61% cover. Copepods dominated the epifauna during the first 3 wk of litter decomposition. In the 4 to 5 wk old litter, polychaetes were most abundant whereas nematodes were dominant in litter that had decomposed for 8 wk. PL foraging on 4 wk old litter had a higher SGR (1.6 +/- 0.5%) and SR (39.8 +/- 4.8%) coincident with the maximum abundance of microalgae and epifauna. The study illustrated that nutritionally rich biofilm for PL shrimp is: (1) developed during the fourth week of mangrove leaf litter decomposition and is dominated by diatoms, polychaetes, harpacticoid copepods, and oligochaetes; and (2) limited by the collapse of the epifauna and subsequent colonization by cyanobacteria in mangrove leaf litter decomposed beyond 4 wk