
Jose Luis VarelaUniversity of Cadiz, Puerto Real, Spain · Biology Department
Jose Luis Varela
PhD
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62
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Introduction
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June 2014 - June 2015
Publications
Publications (62)
El atún rojo del sur (Thunnus maccoyii, SBT) se distribuye ampliamente en regiones templadas del hemisferio sur, desde la que los ejemplares adultos migran a la única zona de puesta conocida, situada entre Java y Australia. El atún blanco (Thunnus alalunga, ALB) es un depredador epi-mesopelágico migrador que habita mares tropicales y templados de t...
The Atlantic bluefin tuna (ABFT) population ranges throughout the Atlantic Ocean and Mediterranean Sea, and consists of multiple contingents that use diverse habitats and show different movement patterns over the life cycle. Based on body size, elemental and isotopic data of C and N in muscle and liver, we analysed eastern-stock ABFT by comparing m...
Knowledge about sex‐specific difference in life‐history traits—like growth, mortality, or behavior—is of key importance for management and conservation as these parameters are essential for predictive modeling of population sustainability. We applied a newly developed molecular sex identification method, in combination with a SNP (single nucleotide...
The gills and skin microbiota and microbiome of wild fish remain far more under-investigated compared to that of farmed fish species, despite that these animal-microbe interactions hold the same ecophysiological roles in both cases. In this study, the gills and skin bacterial microbiota profiles and their presumptive bacterial metabolisms were inve...
Bullet tuna (BLT), Auxis rochei, and frigate tuna (FRI), Auxis thazard, are globally exploited wide-ranging species. These anatomically similar tunas may share pelagic habitats in the Atlantic Ocean and Mediterranean Sea. Feeding patterns were investigated in BLT and FRI individuals caught in the Gulf of Cadiz (East Atlantic) in 2019-2021 with the...
The gills and skin microbiota and microbiome of wild fish remain far more under-investigated compared to that of farmed fish species, despite that these animal-microbe interactions hold the same ecophysiological roles in both cases. In this study, the gills and skin bacterial microbiota profiles and their presumptive bacterial metabolisms were inve...
Bioaccumulation patterns of heavy metals (Pb, Cd, Cr, Ni, Fe and Cu) and organic (priority and emerging) pollutants, in combination with stable isotope analysis (SIA), were assessed in muscle and liver of three tuna species from the Gulf of Cadiz (Atlantic bluefin tuna, Thunnus thynnus; Atlantic bonito, Sarda sarda, and skipjack tuna, Katsuwonus pe...
ABSTRACT. Two distinct contingents of Atlantic bluefin tuna (ABFT), Thunnus thynnus (Linnaeus, 1758), occur in the Strait of Gibraltar (SoG): long-term residents and migrants. Long-term residents are commercially exploited all year round, while migrants are caught by traps on their migratory route towards Mediterranean spawning grounds. Although mi...
Atlantic bluefin tuna (ABFT; Thunnus thynnus) spawn primarily in the Gulf of Mexico and Mediterranean Sea, but migrate to foraging habitats throughout the North Atlantic where they are the target of commercial and recreational fisheries. Their natal origin has been characterized through otolith oxygen isotope analysis to link fish on both spawning...
Chemical fingerprints in otoliths are commonly used as natural habitat markers in fishes. Alternatively, the first dorsal fin spine can provide valuable chemical information and may be more suitable for studying (i) endangered fish species that cannot be sacrificed for their otoliths or (ii) fishes for which otoliths might not be available because...
Two distinct contingents of Atlantic bluefin tuna (ABFT), migrants and residents, occur in the Strait of Gibraltar (SoG). Long-term residents are commercially exploited all year round using hook and line gears, whereas migrants are caught by traps in springtime as they pass through the SoG towards Mediterranean spawning grounds. While reproductive...
The Canary archipelago, which is part of the Atlantic biogeographical region of the Macaronesia, provides an appropriate habitat for tropical and temperate-water large pelagics. Atlantic bluefin tuna (ABFT, Thunnus thynnus) occur all year round in the Canary Islands. Life history traits of ABFT, specifically foraging patterns, have not been studied...
This study presents information about trophic relationships between juvenile albacore (ALB, Thunnus alalunga) and skipjack tuna (SKJ, Katsuwonus pelamis) in the Gulf of Cadiz (East Atlantic Ocean). Data on stomach contents (SCA) and stable isotope ratios of carbon and nitrogen (SIA) were analyzed to ascertain foraging patterns and trophic niche bre...
Feeding habits of common dolphinfish (Coryphaena hippurus) were investigated in the Southeast Pacific Ocean using stomach content analysis. Stomachs were collected from 1506 individuals ranging between 18 and 187 cm in fork length. The fish were caught by longliner boats in 2009–2017. Based on percentage of wet weight (%W𝑖), percentage of number (%...
Seagrasses, as key ecosystem engineers in coastal ecosystems, contribute to enhancing diversity in comparison with nearby bare areas. It has been proved mainly for epifauna, but data on infauna are still scarce. The present study addresses how seagrass structural complexity (i.e., canopy properties) affects the diversity of infaunal organisms inhab...
This study aims to analyze the effect of the trophic interaction between bullet tuna (BT), Auxis rochei (Risso, 1810), and Atlantic bluefin tuna (ABFT), Thunnus thynnus (Linnaeus, 1758) on larval growth. We examined the influence of feeding behavior on larval growth considering environmental variables, daily growth metrics, otolith biometry, stable...
Anadromous alewife Alosa pseudoharengus (n = 202; mean ± s.d. fork length = 231 ± 14 mm) were captured from 10 May to 27 June 2018 in an upper watershed lake on the Isthmus of Chignecto, Canada (45°57′N, 64°14′W). Thirty individuals (mean ± s.d. fork length = 250 ± 12 mm) were captured in an adjacent estuary downstream of a tide gate on 25 April 20...
In this study, the authors examined late atretic follicles in the ovaries of Atlantic bluefin tuna, Thunnus thynnus (Linnæus 1758), at different times of the year using transmitted light and epifluorescence microscopy. Atresia (degeneration and resorption of developing ovarian follicles) is a natural process involved in fecundity downregulation in...
Feeding habits, diets and trophic relationships among three demersal sharks (Galeus melastomus Rafinesque, 1810; Etmopterus spinax (Linnaeus, 1758); and Scyliorhinus canicula (Linnaeus, 1758)) from the Porcupine Bank, Northeast Atlantic were studied. The stomach content analysis revealed differences between the diet of the three species, with a cle...
Feeding ecology of Atlantic bluefin tuna (ABFT, Thunnus thynnus), from the Gulf of Saint Lawrence, Canada, was assessed by stomach content and stable isotope analyses. Stomachs were collected from 161 individuals averaging 249 ± 20 cm in curved fork length and 248 ± 64 in round weight. The fish were caught by commercial fishing boats using rod and...
Trophic ecology studies of top predator species, such as elasmobranchs, is crucial to understand their ecological role. Here, we present preliminary results on the feeding habits of the blackmouth catshark, Galeus melastomus, a small bottom-dwelling shark widely distributed in the northeast Atlantic. This species is the most abundant shark of the P...
The blackmouth catshark (Galeus melastomus) is one of the most abundant elasmobranch in Porcupine Bank, mainly caught as by-catch and largely discarded. In terms of abundance and biomass this species seems to have a particular importance from the point of view of the marine ecosystem. In the present study, we provide a quantitative description of t...
This study provides sound evidence of the spawning activity of common dolphinfish (Coryphaena hippurus) in the Gulf of Cadiz (southwest Spain) during summer months. Along with waters off Côte d'Ivoire, this area adjacent to the Mediterranean Sea is the easternmost Atlantic spawning ground documented for the species. All the fish analysed (5 males a...
Foraging habits of skipjack tuna, SKJ (Katsuwonus pelamis), were investigated in three Spanish marine regions (Balearic Sea, Alboran Sea and Gulf of Cadiz) using stomach content (SCA), stable isotope (SIA), and fatty acid (FA) analyses. The three methodological approaches yielded significant differences among locations. All the studied areas appear...
The food habits of the South Pacific hake (Merluccius gayi) from Ecuadorian waters were studied by analysing 232 stomachs of specimens ranging from 23.4 to 83.1 cm in total length (TL). Fish was the most important prey group (Alimentary Index, %AI=94), Ctenosciaena peruviana being the most represented prey species (%AI = 62.17). PERMANOVA analysis...
The Strait of Gibraltar (SoG) houses a large diversity of marine species including large pelagic animals that use this area as permanent or temporary habitat. In particular, the SoG is home to a population of adult and sub-adult Atlantic bluefin tuna (Thunnus thynnus) that occurs there for most of the year. To gain further insight into the life his...
Effective sustainable management of marine fisheries requires that assessed management units (that is, fish stocks) correspond to biological populations. This issue has long been discussed in the context of Atlantic bluefin tuna (ABFT, Thunnus thynnus) management, which currently considers two unmixed stocks but does not take into account how indiv...
The Atlantic tarpon Megalops atlanticus Valenciennes, 1847 is a very large, highly migratory fish that frequents coastal and inshore waters. Its distribution ranges the western Atlantic, from Nova Scotia to Argentina, the eastern Pacific, near the opening of the Panama Canal, and the eastern Atlantic, mainly along the west coast of Africa, from Mau...
The Alboran Sea holds one of the highest biological productivity rates in the Mediterranean, and thus represents an important nursing area for pelagic fishes including tunas. Trophic interactions between sympatric populations of age-0 bluefin tuna (ABFT) and Atlantic bonito (BON) were investigated in Alboran by integrating stomach content analysis...
Mass mortality is still one of the main constraints in larval rearing of Atlantic bluefin tuna (Thunnus thynnus L.; ABT). Early data related to the feeding sequence of ABT larvae suggested that mortality observed during the first stages of life could be partly due to nutritional deficiencies. Previous studies demonstrated that copepods appeared to...
Keywords: Thunnus Diet Feeding ecology Stomach content analysis (SCA) Bulk stable isotope analysis (BSIA) Amino acid stable isotope analysis (AA-CSIA) A B S T R A C T The trophic biology of age-0 Thunnus thynnus (ABFT) was investigated at two locations off the Iberian Mediterranean coast (Cambrils and Valencia) between 2012 and 2014 using stomach c...
Underwater PSAT tagging of bluefin tuna in purse-seine nets 2013
Underwater PSAT tagging of bluefin tuna in purse-seine nets 2009
Stable isotope analysis (δ13C and δ15N from liver and muscle) was used to assess trophic relationships between Atlantic bluefin tuna (ABFT) (Thunnus thynnus) and striped dolphin (SC) (Stenella coeruleoalbla) in the Strait of Gibraltar (SoG). δ15N values from ABFT muscle and liver tissues were significantly different from those of dolphin samples, b...
Environmental contamination by mercury is a concern in marine food webs, and especially for large fish. We
examined methylmercury (MeHg) levels in blood, muscle and liver of 35 individual Atlantic sturgeon (Acipenser
oxyrhynchus), a commercially harvested, anadromous fish eastern Canada. Females had higher blood and liver
MeHg levels than males, an...
The feeding ecology and consumption rate of the broadbill swordfish (Xiphias 16 gladius) from Ecuadorian waters were assessed by stomach content analysis of 256 17 individuals ranging between 91 and 291 cm in straight for length (FL). Based on the 18 alimentary index (%AI), the jumbo squid (Dosidicus gigas) was the most important 19 prey species (5...
Size-related shifts in feeding habits of juvenile yellowfin tuna (YFT), Thunnus albacares (Bonnaterre, 1788), in Ecuadorian waters were assessed using stomach content analysis (SCA) (n=339) and stable isotope analysis (n = 83). In all size classes, fishes were the predominant prey group in the diet (Alimentary Index, %AI = 96.86) followed by cephal...
The diet of Atlantic bluefin tuna (ABFT), Thunnus thynnus, caught in the Strait of Gibraltar area (SoG) from late summer through fall was assessed by stomach content (SCA) and stable isotope (SIA) analyses. Our results show that the SoG provides suitable food resources for sub-adult and adult ABFT. The SCA did not show inter-annual differences, and...
The diet and the feeding habits of the common dolphinfish (Coryphaena hippurus) in the Pacific coast of Ecuador was assessed by examining 320 stomachs of individuals ranging from 51 to 149 cm in total length. Fish was the predominant prey group in the diet (Alimentary Index, %AI ¼ 95.39) followed by cephalopods (%AI ¼ 4.13) and crustaceans (%AI ¼ 0...
Knowing how migratory pelagic predators use food web resources during early life stages is essential for understanding population dynamics and recruitment. Feeding habits of ~3 to 4 mo old Atlantic bluefin tuna (ABFT) Thunnus thynnus from 2 Mediterranean nearshore areas (Cartagena and Cambrils, Spain) showing distinct oceanographic features were in...
The aim of this study was to evaluate the inclusion of two macroalgae as dietary ingredients on growth, body composition, intermediate metabolism, intestinal enzymes and gut histology of Sparus aurata juveniles. Six isocaloric and isonitrogenous diets incorporating 5%, 15% or 25% of Gracilaria cornea or Ulva rigida meal were tested against a contro...
The diet of young Atlantic bluefin tuna (Thunnus thynnus) in the Bay of Biscay foraging ground was assessed using stomach-content analysis (SCA) and stable-isotope analysis coupled with isotope mixing model. Whereas SCA showed that the young tuna fed mainly on horse mackerel (Trachurus trachurus), the estimation of liver and muscle mixing model ana...
Spawning behaviour of Atlantic bluefin tuna (Thunnus thynnus) was investigated using electronic satellite tags deployed in the western Mediterranean spawning ground, around the Balearic Islands (years 2009-2011). All the fish were tagged underwater and released within schools. In general, the fish tagged in the same year/school displayed common mig...
Stomach content analysis (SCA) and stable isotope analysis (SIA) coupled
with isotopic mixing model analysis were used to estimate diet
composition of pre-spawning Atlantic bluefin tuna (ABFT), Thunnus
thynnus, caught by trap in the Strait of Gibraltar area. SCA provided
poor information on diet as most of the stomachs appeared empty or
contained o...
Stable isotope analysis (SIA) has become a useful tool in trophic ecology research, but experimental studies are essential for their correct application in field studies. Young-of-the-year (YOY) Atlantic bluefin tuna (ABFT) caught in the Mediterranean Spanish coast were reared on a common natural prey to determine prey-muscle and prey-liver discrim...
The application of probiotics on aquatic animals is increasing for a better fish welfare status as well as an environment-friendly activity which are actual demands of modern aquaculture industry. A bacterium from skin mucus of healthy gilthead seabream (Sparus aurata L.) has been isolated and identified as Shewanella putrefaciens Pdp11. Different...
The effects of dietary administration of probiotic Pdp11, a bacterial probiotic strain from the Alteromonadaceae family, on growth and stress tolerance to high stocking density was analyzed in juvenile gilthead sea bream Sparus auratus. In the first trial, juvenile specimens were fed during 116 days with control feed or diets supplemented with Pdp1...
The impact of cadmium on metabolism and osmoregulation was assessed in gilthead sea bream (Sparus aurata). Seawater acclimated fish were injected intraperitoneally with a sublethal dose of cadmium (1.25 mg Cd/kg body wt). After 7 days, half of the injected fish were sampled. The remaining fish were transferred to hypersaline water and sampled 4 day...
Questions
Questions (2)
Hi everybody,
I want to run MixSIAR for H. diverscolor and S plana, but I am not sure about which TEF I should use. Does anyone have information on specific TEFs for these species? I have read the paper published by Rossi et al (2015), but I do not feel really comfortable using the same TEF for both species. Any suggestion will be very welcome.
Saludos
Jose Luis
It was found off Ecuador (Manabi province). Thanks a lot!
Jose Varela