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Phytoplankton community and primary production in the Caribbean waters: the biological oceanography component of the LAPE Project

Scientific Basis for Ecosystem-Based Management in the Lesser Antilles Including Interactions with Marine Mammals and Other Top Predators (LAPE)







Scientific Basis for Ecosystem-Based Management in the Lesser Antilles Including Interactions with Marine Mammals and Other Top Predators: Phytoplankton Community and Primary Production in the Caribbean Waters: the Biological Oceanography Component of the LAPE Project, by Marie-Hélène Forget, PhD, FAO, Barbados, 2008. ix + 88 pp., 8 Tables and 20 Figures, FI:GCP/RLA/140/JPN. Technical Document No. 5


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    Project
    Cruise report for the LAPE ecosystem survey on RV Celtic Explorer (CE0607)
    Scientific Basis for Ecosystem-Based Management in the Lesser Antilles Including Interactions with Marine Mammals and Other Top Predators (LAPE)
    2006
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    The LAPE project has completed an ecosystem survey using the research vessel R/V Celtic Explorer, operated from Galway, Ireland by the Marine Institute. The survey collected information on the abundance, biomass and distribution information for pelagic forage species, as well as sampling for trophic relationships and physical and biological environmental sampling. This includes samples from numerous species rarely or never observed when sampling from fisheries catches. Acoustic bioma ss estimates have not been completed however the greatest biomass of forage species detected, both acoustically and by trawling, is predominantly mesopelagic fish, squids and crustaceans. The catches of epipelagic species were mostly juveniles of oceanic pelagic, coastal pelagic and reef species. This survey did not target, and did not catch, the commercially important pelagic species of the region. Flyingfish (Exocetidae) and dolphin (Coryphaena hippurus) are known to occur only w ithin a few meters of the surface, above both the acoustic transducers and the minimum fishing depth of the trawls. In addition, these and the adults of the other large pelagic species (Istiophoridae, Scombridae, Xiphiidae) are too fast and agile to be easily caught using pelagic trawls. The ecosystem survey also provided in-situ measures of biological oceanographic parameters to calibrate satellite estimates of primary productivity as well as information on key physical parameters of the water masses in the region. Preliminary inspection of the cruise results are all largely consistent with expected conditions in oligotrophic tropical oceanic waters (Longhurst, 1999). The primary production is limited to deep chlorophyll layers with essentially no chlorophyll or fluorescence measurable in near-surface waters. A cetacean sighting survey was conducted during daylight along the same transects. Although previous surveys have shown that the region does not have high concentrations of cetaceans the cetacean results are still surprisingly low. Since data are too few for a statistical analysis, a careful review of the cetacean survey is required to understand these extremely low results.
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    Outline of climate and oceanographic conditions in the Indian Ocean in the recent years: an update to August 2013 2013
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    In this paper, we provide an update on the trends of climate and oceanographic conditions in the Indian Ocean and in sub-regions (Somali basin, East and West Equatorial areas, Mozambique Channel and Maldives). The ENSO cycle has been largely fluctuating between ENSO-neutral and Niña conditions during the past 4 years. Positive sea surface temperature (SST) anomalies have prevailed since the early 2000 over the West Indian Ocean (WIO). Substantial deepening of the thermocline occurs in the WIO in relation with intense El Niño events, but the opposite response (shoaling) during La Niña events is not clear on the long term. Since 2008, SOI has shown predomintly positive values (Niña) and thermocline has shoaled without major disruption along this trend until April 2011. Chlorophyll (SSC) has shown a declining trend over 2006-2010, followed by a slight increase from October 2010 to May 2011 in association with a Niña event, then continued to decline until March 2013. Then, the trend revers ed and positive anomalies developed from May 2013 onwards. Highly positive SSC anomalies were found in July-September 2013 in the Somali basin (40% above normal), suggesting an intensification of the Somali upwelling. In other areas, SSC was about the average in 2013 (Mozambique Channel, Maldives) or still slightly negative (10 % below normal) in the West equatorial (December 2012 to February 2013) and East equatorial areas. The overall chlorophyll- depleted conditions for 2006-2012 (except 2011 ) in the WIO, when the thermocline was shoaling, is unclear as we might have expected a positive chlorophyll response to an increased supply of nutrients in the photic layer associated with shallow thermocline. The skipjack purse seine CPUEs on associated sets, in the Somali basin during July-September, are distributed in chlorophyll-enriched areas resulting from the upwelling. In 2010-2012, the position of the 0.4 mg.m-3 isoline of chlorophyll concentration delineated the eastward boundary of t he skipjack CPUEs.
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    Impact of dipole mode and El-Nino events on catches of yellowfin tuna (Thunnus albacares) in the Eastern Indian Ocean off west Java 2013
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    The impact of Indian Ocean Dipole Mode (IOD) and El Niño-Southern Oscillation (ENSO) events on catches of yellowfin tu (Thunnus albacares) (YFT) in the Eastern Indian Ocean (EIO) off Java was alyzed through the use of remotely sensed environmental data (sea surface temperature/ SST and chlorophyll-a concentration/ SSC) and yellowfin tu catch data. Alyses were conducted for the period of 2003–2012, which included the strong positive dipole mode event in association with weak ENSO in 2006. Yellowf in tu catch data were based from the report of Palabuhanratu fishing port and remotely sensed environmental data were based from MODIS-Aqua_NOAA. IOD has a significant effect on the catch composition and proportion of YFT. In the strong positive dipole mode event in 2006 and weak ENSO events in 2011 and 2012 the catch of YFT was higher than normal period. An increasing Catch Per Unit Effort (CPUE) of YFT started from May-June and reached the peak on September-October was noted, this might be due to upwelling evident before the increasing trend observed. High increase of YFT-CPUE occurred during strong positive dipole mode event (2006) and a weak ENSO events (2011 and 2012) might be related to the increase of abundance and distribution of chlorophyll-a and phytoplankton in those period. In contrast, YFT- CPUE was very low at the La-Ni event in 2005 while this species was still domint in the catch composition compared to other tu species.

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