Benbow S.,Omnibus Business Center |
Humber F.,Omnibus Business Center |
Oliver T.A.,Omnibus Business Center |
Oliver T.A.,Hawaii Institute of Marine Biology |
And 7 more authors.
African Journal of Marine Science | Year: 2014
This paper presents evidence of the fisheries effect of experimental temporary fishing closures for Octopus cyanea in the then-emergent Velondriake Locally Managed Marine Area (LMMA) in south-west Madagascar during 2004-2006. We present an analysis of the O. cyanea catch data for the first two years of temporary closures based on landings data collected from village-based octopus collectors. We found a significant closure effect in terms of total weight and number of octopus caught on opening days, but observed that these benefits dissipated quickly, returning to pre-closure levels within days. Mean octopus size increased by 41% on average when compared to data from selected control sites. However, extremely high levels of fishing effort on opening days meant that these biological effects did not translate into increased weight of octopus caught per successful fisher over the opening tide. Upon opening of concurrent closures during the second round of closures we found significant increases in the weight of octopus caught per successful fisher. We conclude that the pilot closures had a significant closure effect, but caution against isolated openings leading to concentrated fishing effort on opening days. © 2014 Copyright © NISC (Pty) Ltd.
Andrefouet S.,CIRAD - Agricultural Research for Development |
Guillaume M.M.M.,French Natural History Museum |
Guillaume M.M.M.,University of Reunion Island |
Delval A.,University of Reunion Island |
And 3 more authors.
Coral Reefs | Year: 2013
The Grand Récif of Toliara (GRT) in Madagascar is a large (33 km2) barrier reef system of the SW Indian Ocean that had been well investigated in the 1960s and early 1970s. A massive degradation of the reef has been reported since at least the early 1980s, just a few years after research activities ceased in the area. Examination of historical aerial photographs and modern high-resolution remote sensing images confirms a continuous loss of coral habitat on GRT outer reef flats between 1962 and 2011, with an average loss of 65 % and a range of 37-79 % loss during this 50-year period. The usual suspects of coral community declines (cyclones, bleaching and sedimentation) may have contributed to the demise of the GRT. However, an independent study (Salimo 1997) suggests that the chronic pressure of fisherman gleaning on reef flats with destructive tools is the main driver of the observed changes. Salimo's reported level of frequentation (6.8 fishermen per day and per km-2) and rates of destruction per fisherman (7.7 m2 of coral habitat h-1) yield a cumulated overall loss in agreement with the image-based rates of habitat loss. The GRT is unlikely to recover because this chronic stress is unlikely to decrease in the near future. Indeed, the GRT daily provides subsistence fishery resources for local Vezo people and to agriculturalist or pastoralist ethnic groups who have turned to exploiting coastal resources due to increasing aridity and dwindling agricultural and livestock production. © 2013 Springer-Verlag Berlin Heidelberg.
Raberinary D.,Omnibus Business Center |
Raberinary D.,Institute Halieutique et des science Marines |
Benbow S.,Omnibus Business Center
Fisheries Research | Year: 2012
The Octopus cyanea fishery is the most economically important fishery in southwest Madagascar. Growing concerns over the sustainability of exploitation have promoted a number of conservation efforts to improve management of the fishery. We analyse one year of catch data to identify seasonal variations in sexual maturity and key reproductive periods of the species, using microscopic analysis of gonad tissues to validate field assessments of maturity. Data show seasonal variability in maturity and size at first maturity for both sexes, as well as temporal changes in the sex ratio of the species. Maturity occurred at a minimum mean weight of 2246. g for females and 643. g for males. A clear relationship between gonad weight and total weight in male octopus indicates that total weight can be used as a proxy for sexual maturity in males. Conversely, females show high variability in weight at first maturity and no clear relationship between total weight and maturity stage. Fully sexually mature females were very rare, constituting less than 1% of the total sample. We hypothesise that the artisanal fishery may not be currently exploiting mature female individuals because females retreat to deeper waters prior to reproduction, thus remaining beyond the reach of the fishery. An abundance of juvenile individuals in the catch from June, and again from October to November, indicates recruitment peaks at these two times. In recent years, management of this species in southwest Madagascar has focused on short-term closures to fishing within specific tidal reef flat areas. Identification of the key phases of the reproductive cycle of O. cyanea in southwest Madagascar may provide managers with biological evidence to support seasonal closures designed to protect key life stages of the species. © 2012 Elsevier B.V.
Henrich Bruggemann J.,University of Reunion Island |
Henrich Bruggemann J.,Laboratoire dExcellence CORAIL |
Rodier M.,Institute Of Recherche Pour Le Developpement |
Guillaume M.M.M.,University of Reunion Island |
And 12 more authors.
Ecology and Society | Year: 2012
High-latitude coral reefs may be a refuge and area of reef expansion under climate change. As these locations are expected to become dryer and as livestock and agricultural yields decline, coastal populations may become increasingly dependent on marine resources. To evaluate this social-ecological conundrum, we examined the Grand Récif of Toliara (GRT), southwest Madagascar, which was intensively studied in the 1960s and has been highly degraded since the 1980s. We analyzed the social and ecological published and unpublished literature on this region and provide new data to assess the magnitude of the changes and evaluate the causes of reef degradation. Top-down controls were identified as the major drivers: human population growth and migrations, overfishing, and climate change, specifically decreased rainfall and rising temperature. Water quality has not changed since originally studied, and bottom-up control was ruled out. The identified network of social-ecological processes acting at different scales implies that decision makers will face complex problems that are linked to broader social, economic, and policy issues. This characterizes wicked problems, which are often dealt with by partial solutions that are exploratory and include inputs from various stakeholders along with information sharing, knowledge synthesis, and trust building. A hybrid approach based on classical fishery management options and preferences, along with monitoring, feedback and forums for searching solutions, could move the process of adaptation forward once an adaptive and appropriately scaled governance system is functioning. This approach has broad implications for resources management given the emerging climate change and multiple social and environmental stresses. © 2012 by the author(s).