Validating an ecological model with fisheries management applications: the relationship between loggerhead by-catch and distance to the coast

On the one hand, a recent study on sea turtle by-catch during surface longline fishing targeting swordfish in the western Mediterranean Sea showed that sea turtle by-catch is independent of fishing effort and other technological factors. When the distance to the coast increases, there is a higher probability of catching a loggerhead turtle. The authors proposed to avoid fisheries further than 35 nautical miles (approximately 65 km) from the coast. However, the proposed 35 nautical miles limit could be useful where the continental shelf is narrow, as in the Balearic Sea, and useless where it widens. On the other hand, ecological model validation is considered essential for management application. The objective of the present paper is to validate the new fisheries loggerhead by-catch model in different areas outside the Balearic Sea with wider continental shelves, aimed at maintaining sustainable fishing activity compatible with the conservation of the loggerhead populations. Our present results validate the previous model, and stress the importance of the eco-geographical variable distance to the coast in understanding the loggerhead by-catch (or incidental capture) per unit effort for the longline fisheries targeting swordfish.

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Interannual Differences for Sea Turtles Bycatch in Spanish Longliners from Western Mediterranean Sea

The Scientific World JOURNAL ◽

10.1155/2014/861396 ◽

2014 ◽

Vol 2014 ◽

pp. 1-7 ◽

Cited By ~ 5

Author(s):

José C. Báez ◽

David Macías ◽

Salvador García-Barcelona ◽

Raimundo Real

Keyword(s):

Mediterranean Sea ◽

Loggerhead Turtle ◽

Sea Turtle ◽

Western Mediterranean ◽

Climatic Conditions ◽

Fishing Activity ◽

Leatherback Turtles ◽

Leatherback Turtle ◽

Western Mediterranean Sea ◽

Loggerhead Turtles

Recent studies showed that regional abundance of loggerhead and leatherback turtles could oscillate interannually according to oceanographic and climatic conditions. The Western Mediterranean is an important fishing area for the Spanish drifting longline fleet, which mainly targets swordfish, bluefin tuna, and albacore. Due to the spatial overlapping in fishing activity and turtle distribution, there is an increasing sea turtle conservation concern. The main goal of this study is to analyse the interannual bycatch of loggerhead and leatherback turtles by the Spanish Mediterranean longline fishery and to test the relationship between the total turtle by-catch of this fishery and the North Atlantic Oscillation (NAO). During the 14 years covered in this study, the number of sea turtle bycatches was 3,940 loggerhead turtles and 8 leatherback turtles, 0.499 loggerhead turtles/1000 hooks and 0.001014 leatherback turtles/1000 hooks. In the case of the loggerhead turtle the positive phase of the NAO favours an increase of loggerhead turtles in the Western Mediterranean Sea. However, in the case of leatherback turtle the negative phase of the NAO favours the presence of leatherback turtle. This contraposition could be related to the different ecophysiological response of both species during their migration cycle.

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Differential distribution within longline transects of loggerhead turtles and swordfish captured by the Spanish Mediterranean surface longline fishery

Journal of the Marine Biological Association of the United Kingdom ◽

10.1017/s0025315407054744 ◽

2007 ◽

Vol 87 (3) ◽

pp. 801-803 ◽

Cited By ~ 17

Author(s):

José C. Báez ◽

Raimundo Real ◽

Juan A. Camiñas

Keyword(s):

Loggerhead Turtle ◽

Western Mediterranean ◽

Differential Distribution ◽

Chi Square ◽

Western Mediterranean Sea ◽

Loggerhead Turtles ◽

Chi Square Test ◽

Incidental Catch ◽

By Catch ◽

The Relationship

Surface longline targeting mainly swordfish is considered a major threat for loggerhead turtle populations in the western Mediterranean Sea. For this reason, it is necessary to analyse the relationship between the characteristics of longline sets and loggerhead turtle by-catch. The objective of this study is to look for differential spatial distribution of loggerhead turtle and swordfish captures along the longline to gain insights that might be useful to diminish unintended, incidental catch of turtles without affecting the captures of the target species.Longlines are divided into transects separated by two consecutives buoys. During the 1999 fishing period of the traditional (without roller) Spanish surface drifting longline fleet (August to November), 59 technically homogeneous fishing operations, composed of 23 sections each, were observed. Chi-square test was used to compare loggerhead turtle and swordfish distributions among transects with those expected at random. Significant differences were obtained only for loggerhead turtles, with 93% of the specimens caught in the second half of the longline transects, which were retrieved from the sea during daytime. Significant differences were not found for the swordfish along the whole longline or for loggerhead turtle captures retrieved during daytime. We conclude that swordfish captures are independent of retrieval time whereas the incidental catch of loggerhead turtles occurs mainly during daytime, probably because loggerhead turtles use vision to locate baits.

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New record of a sharpnose sevengill sharkHeptranchias perlo(Elasmobranchii, Hexanchidae) from the Balearic Sea, western Mediterranean Sea

Journal of Fish Biology ◽

10.1111/jfb.13905 ◽

2019 ◽

Vol 94 (3) ◽

pp. 526-531

Author(s):

Javier Guallart ◽

Gabriel Morey ◽

Àlex Bartolí

Keyword(s):

Mediterranean Sea ◽

New Record ◽

Western Mediterranean ◽

Western Mediterranean Sea ◽

Balearic Sea

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Mobulid rays feed on euphausiids in the Bohol Sea

Royal Society Open Science ◽

10.1098/rsos.161060 ◽

2017 ◽

Vol 4 (5) ◽

pp. 161060 ◽

Cited By ~ 28

Author(s):

Christoph A. Rohner ◽

Katherine B. Burgess ◽

Joshua M. Rambahiniarison ◽

Joshua D. Stewart ◽

Alessandro Ponzo ◽

...

Keyword(s):

Life History ◽

Food Resource ◽

Stomach Contents ◽

Fishing Effort ◽

Fishing Activity ◽

Prey Preferences ◽

Manta Birostris ◽

History Of ◽

By Catch ◽

Mobula Japanica

Mobulid rays have a conservative life history and are caught in direct fisheries and as by-catch. Their subsequent vulnerability to overexploitation has recently been recognized, but fisheries management can be ineffective if it ignores habitat and prey preferences and other trophic interactions of the target species. Here, we assessed the feeding ecology of four mobulids ( Manta birostris , Mobula tarapacana , M. japanica , M. thurstoni ) in the Bohol Sea, Philippines, using stomach contents analysis of fisheries specimens landed between November and May in 2013–2015. We show that the mobulids feed heavily on euphausiid krill while they are in the area for approximately six months of the year. We found almost no trophic separation among the mobulid species, with Euphausia diomedeae as the major prey item for all species, recorded in 81 of 89 total stomachs (91%). Mobula japanica and M. thurstoni almost exclusively had this krill in their stomach, while M. tarapacana had a squid and fish, and Ma. birostris had myctophid fishes and copepods in their stomachs in addition to E. diomedeae . This krill was larger than prey for other planktivorous elasmobranchs elsewhere and contributed a mean of 61 364 kcal per stomach (±105 032 kcal s.e., range = 0–631 167 kcal). Our results show that vertically migrating mesopelagic species can be an important food resource for large filter feeders living in tropical seas with oligotrophic surface waters. Given the conservative life history of mobulid rays, the identification of common foraging grounds that overlap with fishing activity could be used to inform future fishing effort.

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Biology and population dynamics of by-catch fish species of the bottom trawl fishery in the western Mediterranean

Mediterranean Marine Science ◽

10.12681/mms.812 ◽

2014 ◽

Vol 15 (3) ◽

pp. 613 ◽

Cited By ~ 3

Author(s):

F. ORDINES ◽

M.T. FARRIOLS ◽

J. LLEONART ◽

B. GUIJARRO ◽

A. QUETGLAS ◽

...

Keyword(s):

Population Analysis ◽

Conservation Status ◽

Fishing Effort ◽

Western Mediterranean ◽

Distribution Range ◽

Bottom Trawl ◽

Trawl Fishery ◽

Virtual Population ◽

Trawl Fishing ◽

By Catch

The teleosts Chelidonichthys cuculus, Trigloporus lastoviza, Serranus cabrilla and Trachinus draco, are important by-catch species, in terms of landed biomass and commercial value, from the continental shelf bottom trawl fishery off the Balearic Islands (western Mediterranean). The main biological parameters of these species were calculated from monthly biological samplings, and were used along with three years pseudo-cohorts (2008-2010) obtained from monitoring on-board of the bottom trawl fleet, to assess their exploitation level through Virtual Population Analysis (VPA) and Yield per Recruit (Y/R) analysis. Time series of fishery independent indicators based on MEDITS surveys data such as the evolution of the abundance and biomass, the distribution range, and the Conservation Status of Fish b (CSFb), were also analyzed. All four species analyzed showed growth overfishing. The reductions of the fishing effort required to reach the Y/RF0,1 reference point were lower, 66-73% depending on the species, to those reported for the target species M. merluccius (87%), but higher than that reported for M. surmuletus (53%), in the study area in the period 2000-2010. The abundance and biomass, and the distribution range did not show any trend for the period 2001-2011, whereas the CSFb showed signs of recovery that may be due to the displacement of the trawl fishing effort from the shelf to the slope during the last decade. Our results underline the necessary incorporation of monitoring and assessment of by-catch species to the management of fisheries as their populations can show a more pronounced overexploitation than target ones.

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By-catch frequency and size differentiation in loggerhead turtles as a function of surface longline gear type in the western Mediterranean Sea

Journal of the Marine Biological Association of the United Kingdom ◽

10.1017/s0025315412001841 ◽

2013 ◽

Vol 93 (5) ◽

pp. 1423-1427 ◽

Cited By ~ 11

Author(s):

José Carlos Báez ◽

David Macías ◽

Juan Antonio Camiñas ◽

José María Ortiz de Urbina ◽

Salvador García-Barcelona ◽

...

Keyword(s):

Mediterranean Sea ◽

Sea Turtle ◽

Western Mediterranean ◽

Catch Per Unit Effort ◽

Size Selectivity ◽

Loggerhead Turtles ◽

The Mediterranean ◽

By Catch ◽

Catch Rates ◽

The Impact

Fisheries by-catch is considered to be a major threat to loggerhead turtles in the Mediterranean Sea. Technical differences in both gear configurations (e.g. hook and bait type) and fisheries operations carried out by the Spanish Mediterranean surface longline fleet could have an effect on by-catch rates and size selectivity. The aim of the present study was to test the differences in by-catch per unit effort and body size of loggerhead sea turtles caught using different gear types in the Mediterranean surface longline fishery. Our results suggest that differences in the gear type used have an effect on catch rates and size selectivity. Thus, surface longliners targeting albacore (LLALB) using smaller hooks tend to capture smaller loggerheads but have the highest by-catch per unit of effort (BPUE), whereas other longlines, such as surface longliners targeting bluefin tuna (LLJAP) and traditional surface longliners targeting swordfish (LLHB), using larger hooks tend to select the larger animals; moreover, LLHB had the lowest BPUE. Disproportionate rates of fisheries-induced mortality on certain size/age-classes can differentially affect sea turtle populations, as each sea turtle age-class contributes differently to current and future reproduction. Thus, fisheries management should not only be focusing on preserving the large juvenile and mature turtles, but also on reducing the total by-catch. Thus, we recommend encouraging the use of LLHB versus other surface gears. We suggest that it is very important to take into account the gear type (and its particular catch rates) when making inferences about the impact of longline fisheries on sea turtle populations.

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Structure and spatio-temporal dynamics of artisanal fisheries around a Mediterranean marine protected area

ICES Journal of Marine Science ◽

10.1093/icesjms/fsp234 ◽

2009 ◽

Vol 67 (2) ◽

pp. 191-203 ◽

Cited By ~ 66

Author(s):

Aitor Forcada ◽

Carlos Valle ◽

José L. Sánchez-Lizaso ◽

Just T. Bayle-Sempere ◽

Fabio Corsi

Keyword(s):

Protected Area ◽

Marine Protected Area ◽

Temporal Dynamics ◽

Marine Reserve ◽

Fishing Effort ◽

Western Mediterranean ◽

Artisanal Fisheries ◽

Time Data ◽

Western Mediterranean Sea ◽

Spatio Temporal

Abstract Forcada, A., Valle, C., Sánchez-Lizaso, J. L., Bayle-Sempere, J. T., and Corsi, F. 2010. Structure and spatio-temporal dynamics of artisanal fisheries around a Mediterranean marine protected area. – ICES Journal of Marine Science, 67: 191–203. Marine protected areas (MPAs) have been proposed and established throughout the world, but few studies have adequately assessed the spatial adaptations of fishers to the limitations imposed by their placement. The main objectives of this work were to identify and describe the characteristics of the artisanal fisheries around Tabarca Marine Reserve (western Mediterranean Sea) and to define their activity in space and time. Data were collected through questionnaires to fishers and onboard sampling. The artisanal fisheries were complex owing to the multispecific nature of the landings, the variety of gears involved, and their marked seasonality. All boats of the three harbours around the MPA were assessed, for a total of 32 boats. The fishers exploit 18 fishing grounds with eight gear types, for a total of 17 métiers. Mullus trammelnet, Sepia trammelnet, and sparid longline are the most frequently used métiers. The main factors determining the spatial distribution of the fishing effort are proximity to home harbour, habitat heterogeneity, and closeness to the MPA. Total fishing effort appeared slightly concentrated around the MPA, but each métier showed different patterns of effort distribution. Although the sparid gillnet and the sparid longline concentrated along MPA boundaries, the Sepia trammelnet and the Mullus trammelnet did not.

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Decadal changes in hydrographic and ecological time-series in the Balearic Sea (western Mediterranean), identifying links between climate and zooplankton

ICES Journal of Marine Science ◽

10.1093/icesjms/fsn017 ◽

2008 ◽

Vol 65 (3) ◽

pp. 311-317 ◽

Cited By ~ 27

Author(s):

Maria Luz Fernández de Puelles ◽

Juan Carlos Molinero

Keyword(s):

Time Series ◽

Large Scale ◽

Western Mediterranean ◽

Zooplankton Abundance ◽

Atmospheric Variability ◽

Survey Period ◽

Climate Effect ◽

The North ◽

Western Mediterranean Sea ◽

Balearic Sea

Abstract Fernández de Puelles, M. L., and Molinero, J. C. 2008. Decadal changes in hydrographic and ecological time-series in the Balearic Sea (western Mediterranean), identifying links between climate and zooplankton. – ICES Journal of Marine Science, 65: 311–317. We investigated possible relationships between climate, hydrography, and zooplankton abundance in the Balearic Sea (BS), during a 10-year survey period spanning January 1994 to December 2003. It was demonstrated that large-scale atmospheric variability in the North Atlantic (NA) Ocean acts as a driver of regional meteorological variations and hydrographic patterns in the BS. The results also revealed that the variability of copepods, appendicularians, cladocerans, siphonophores, doliolids, and ostracods is closely related to variations in water temperature recorded during strong anomalies of the NA climate (>1 s.d.). Although the time-series that we analysed cover a period that is relatively short for investigating climate effects on marine ecosystems, the statistical results reported were consistent enough to emphasize the NA’s climate effect on the BS. The cascade of links identified by these results should be considered and integrated into the assessment and modelling studies of pelagic ecosystem and biogeochemical fluxes in the western Mediterranean Sea.

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Methods to Reduce Sea Turtle Interactions in the Atlantic Canadian Pelagic Long Line Fleet

10.1101/117556 ◽

2017 ◽

Cited By ~ 1

Author(s):

Zachary T. Sherker

Keyword(s):

Sea Turtles ◽

The United States ◽

Sea Turtle ◽

Fishing Effort ◽

Dermochelys Coriacea ◽

Small Scale ◽

The North ◽

Spatio Temporal ◽

Socio Economic Impact ◽

By Catch

AbstractThis project investigates the role of fisheries management in the conservation of loggerhead (Caretta caretta) and leatherback sea turtles (Dermochelys coriacea), both of which are currently listed as vulnerable by the IUCN (International Union for Conservation of Nature). These species migrate from nesting grounds in South America to feed on gelatinous zooplankton (jellyfish) in the North Atlantic off the coast of the United States and Canada. The seasonal foraging grounds of sea turtles heavily overlap with areas of high fishing effort for the longline tuna and swordfish fleet, a fishery that has significantly high rates of sea turtle incidents. The dynamic nature of sea turtle foraging patterns renders static spatio-temporal fishing area closures ineffective. Rather, turtle by-catch mitigation requires small-scale, event-triggered closures and decentralized management to reduce incidents while minimizing the negative socio-economic impact of area closures on fishermen. A number of methods that increase fishing selectivity have been implemented in other commercial fisheries around the globe and are suggested for the Atlantic Canadian fleet moving forward.

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