Pikesley S.K.,University of Exeter |
Godley B.J.,University of Exeter |
Ranger S.,University of Exeter |
Richardson P.B.,Marine Conservation Society |
Witt M.J.,University of Exeter
Journal of the Marine Biological Association of the United Kingdom | Year: 2014
Concern has been expressed over future biogeographical expansion and habitat capitalization by species of the phylum Cnidaria, as this may have negative implications on human activities and ecosystems. There is, however, a paucity of knowledge and understanding of jellyfish ecology, in particular species distribution and seasonality. Recent studies in the UK have principally focused on the Celtic, Irish and North Seas, but all in isolation. In this study we analyse data from a publicly-driven sightings scheme across UK coastal waters (2003-2011; 9 years), with the aim of increasing knowledge on spatial and temporal patterns and trends. We describe inter-annual variability, seasonality and patterns of spatial distribution, and compare these with existing historic literature. Although incidentally-collected data lack quantification of effort, we suggest that with appropriate data management and interpretation, publicly-driven, citizen-science-based, recording schemes can provide for large-scale (spatial and temporal) coverage that would otherwise be logistically and financially unattainable. These schemes may also contribute to baseline data from which future changes in patterns or trends might be identified. We further suggest that findings from such schemes may be strengthened by the inclusion of some element of effort-corrected data collection. Copyright © 2014 Marine Biological Association of the United Kingdom.
Brooks K.,University of York |
Jeffreys G.,Aberystwyth University |
Perri M.,Megaptera |
Pardigon B.,Marine Conservation Society
Marine and Freshwater Research | Year: 2011
In coastal waters of several locations globally, whale sharks (Rhincodon typus) form seasonal aggregations, most of which largely comprise juvenile males of 48m length. Evaluation of the period that individuals stay within these size- and age-specific groupings will clarify our understanding of the transition between life-stages in this species and how this might affect their long-term conservation. Long-term photo-identification studies in Seychelles and Djibouti provided data to evaluate this. The Seychelles aggregation had 443 individuals averaging 5.8m identified between 2001 and 2009; however, the Djibouti aggregation comprised smaller individuals of 3.7m mean length with 297 individuals identified between 2003 and 2010. In Seychelles, 27% of individuals identified in 2001 were seen again in 2009, while in Djibouti none of the whale sharks identified in 2003 were seen in 2010, although 13% from 2004 were. This suggests that membership periods in the Djibouti aggregation are shorter than in the other juvenile aggregations, such as in Seychelles. Continued photo-identification monitoring of other Indian Ocean aggregations might in time show the next location of these young sharks' life-cycle and thereby allow development of informed national and regional management plans. © CSIRO 2011.
Sequeira A.,University of Adelaide |
Mellin C.,University of Adelaide |
Mellin C.,Australian Institute of Marine Science |
Rowat D.,Marine Conservation Society |
And 3 more authors.
Diversity and Distributions | Year: 2012
Aim Predicting distribution patterns of whale sharks (Rhincodon typus, Smith 1828) in the open ocean remains elusive owing to few pelagic records. We developed multivariate distribution models of seasonally variant whale shark distributions derived from tuna purse-seine fishery data. We tested the hypotheses that whale sharks use a narrow temperature range, are more abundant in productive waters and select sites closer to continents than the open ocean. Location Indian Ocean. Methods We compared a 17-year time series of observations of whale sharks associated with tuna purse-seine sets with chlorophyll a concentration and sea surface temperature data extracted from satellite images. Different sets of pseudo-absences based on random distributions, distance to shark locations and tuna catch were generated to account for spatiotemporal variation in sampling effort and probability of detection. We applied generalized linear, spatial mixed-effects and Maximum Entropy models to predict seasonal variation in habitat suitability and produced maps of distribution. Results The saturated generalized linear models including bathymetric slope, depth, distance to shore, the quadratic of mean sea surface temperature, sea surface temperature variance and chlorophyll a had the highest relative statistical support, with the highest percent deviance explained when using random pseudo-absences with fixed effect-only models and the tuna pseudo-absences with mixed-effects models (e.g. 58% and 26% in autumn, respectively). Maximum Entropy results suggested that whale sharks responded mainly to variation in depth, chlorophyll a and temperature in all seasons. Bathymetric slope had only a minor influence on the presence. Main conclusions Whale shark habitat suitability in the Indian Ocean is mainly correlated with spatial variation in sea surface temperature. The relative influence of this predictor provides a basis for predicting habitat suitability in the open ocean, possibly giving insights into the migratory behaviour of the world's largest fish. Our results also provide a baseline for temperature-dependent predictions of distributional changes in the future. © 2011 Blackwell Publishing Ltd.
Stringell T.B.,University of Exeter |
Calosso M.C.,Center for Marine Resource Studies |
Claydon J.A.B.,Center for Marine Resource Studies |
Godley B.J.,University of Exeter |
And 4 more authors.
Ocean and Coastal Management | Year: 2013
Small-scale fisheries (SSF) account for around half of the world's marine and inland fisheries, but their impact on the marine environment is usually under-estimated owing to difficulties in monitoring and regulation. Successful management of mixed SSF requires holistic approaches that sustainably exploit target species, consider non-target species and maintain fisher livelihoods. For two years, we studied the marine turtle fishery in the Turks and Caicos Islands (TCI) in the Wider Caribbean Region, where the main export fisheries are queen conch (Strombus gigas) and the spiny lobster (Panulirus argus); with fin-fish, green turtles (Chelonia mydas) and hawksbill turtles (Eretmochelys imbricata) taken for domestic consumption. We evaluate the turtle harvest in relation to the other fisheries and recommend legislation and management alternatives. We demonstrate the connectivity between multi-species fisheries and artisanal turtle capture: with increasing lobster catch-per-unit-effort (CPUE), hawksbill catch increased whilst green turtle catch decreased. With increasing conch CPUE, hawksbill catch declined and there was no demonstrable effect on green turtle catch. We estimate 176-324 green and 114-277 hawksbill turtles are harvested annually in TCI: the largest documented legal hawksbill fishery in the western Atlantic. Of particular concern is the capture of adult turtles. Current legislation focuses take on larger individuals that are key to population maintenance. Considering these data we recommend the introduction of maximum size limits for both species and a closed season on hawksbill take during the lobster fishing season. Our results highlight the need to manage turtles as part of a broader approach to SSF management. © 2013 Elsevier Ltd.
Thurstan R.H.,University of York |
Brockington S.,Marine Conservation Society |
Roberts C.M.,University of York
Nature Communications | Year: 2010
In 2009, the European Commission estimated that 88% of monitored marine fish stocks were overfished, on the basis of data that go back 20 to 40 years and depending on the species investigated. However, commercial sea fishing goes back centuries, calling into question the validity of management conclusions drawn from recent data. We compiled statistics of annual demersal fish landings from bottom trawl catches landing in England and Wales dating back to 1889, using previously neglected UK Government data. We then corrected the figures for increases in fishing power over time and a recent shift in the proportion of fish landed abroad to estimate the change in landings per unit of fishing power (LPUP), a measure of the commercial productivity of fisheries. LPUP reduced by 94% - 17-fold - over the past 118 years. This implies an extraordinary decline in the availability of bottom-living fish and a profound reorganization of seabed ecosystems since the nineteenth century industrialization of fishing.