Browsing by Author "Hazin, Fábio H. V."
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- A green strategy for shark attack mitigation off Recife, BrazilPublication . Hazin, Fábio H. V.; André S. AfonsoShark attacks on humans have prompted the implementation of shark control programs aiming at reducing local populations of potentially aggressive species using mostly gillnets. However, shark meshing produces ecological disturbances by inflicting severe mortality not only to sharks but also to several harmless, frequently endangered taxa, including cetaceans, sirenians and chelonids. A different methodological approach to mitigate shark peril off Recife combines bottom longlining and drumlines with comparably better results. This region has been experiencing an abnormally high shark attack rate since 1992, but the protective fishing strategy was developed in 2004 only. Unlike traditional shark control programs, the Shark Monitoring Program of Recife (SMPR) aims at removing dangerous sharks not from their populations but from the hazardous area instead, which is achieved by capturing, transporting and releasing sharks offshore. During 8 years, the SMPR caught fish and turtles only and showed high selectivity for sharks compared with shark meshing. Target species comprised carcharhinids and sphyrnids and accounted for 7% of total catch. The fishing mortality of abundant taxa was generally low except for Carcharhinus acronotus and Gymnothorax spp., and protected species had similar to 100% survival. The shark attack rate diminished about 97% while fishing operations were being conducted (W = 1108.5, P < 0.001), whereas no-fishing periods and the period prior to the implementation of the SMPR had similar shark attack rates. Overall, the SMPR seems to be less detrimental than shark meshing strategies while clearly contributing for enhancing bather safety; thus, it may provide an effective, ecologically balanced tool for assisting in shark attack mitigation.
- An updated revision of shortfin mako size distributions in the AtlanticPublication . Coelho, Rui; Domingo, A.; Courtney, D.; Cortés, E.; Arocha, F.; Liu, K-M; Yokawa, K.; Yasuko, S.; Hazin, Fábio H. V.; Bowlby, H.; Abid, N.; Rosa, D.; Lino, PedroAs part of an ongoing cooperative program for fisheries and biological data collection within the ICCAT Sharks Working Group, information collected by fishery observers and scientific projects from several fishing nations in the Atlantic were analyzed. Datasets included information on geographic location, size and sex. A total of 42,979 shortfin mako records collected between 1989 and 2017 were compiled. Sizes considered ranged between 60 and 353 cm FL (fork length). Of those, sex information was available for 24,316 specimens. Considerable variability was observed in the size distribution by region and season, with larger sizes tending to occur in equatorial and tropical regions and smaller sizes in higher latitudes. Variability between coastal and more oceanic waters is also likely. Most fleets showed unimodal distributions, but in some cases there were bimodal patterns. The distributional patterns presented in this study provide an advance in the understanding of shortfin mako size distribution in the Atlantic, and can be used in the next update of the ICCAT shortfin mako stock assessment.
- Effect of light-sticks and electralume attractors on surface-longline catches of swordfish (Xiphias gladius, Linnaeus, 1959) in the southwest equatorial AtlanticPublication . Hazin, H. G.; Hazin, Fábio H. V.; Travassos, P.; Erzini, KarimTwo experimental fishing trials were carried out off the coast of Pernambuco, Brazil, in 1999 and 2001, using a small artisanal longliner. In experiment 1, six-hook baskets with three chemical light-sticks on alternating hooks had significantly higher catch rates than those with zero or with a light-stick on every hook, with most swordfish accounted for by hooks with light-sticks. Analysis of the data from experiment 2 showed no significant difference between electralume attractors, consisting of AA lithium batteries protected by a solid cover and light-sticks that produce a fluorescent light when two chemical products are mixed. Significant differences were detected in mean CPUE by size class, with most swordfish belonging to class ‘b’ (125–170 cm lower jaw to fork length (LJFL)). No differences, however, were found for swordfish catches in classes ‘a’ (<125 cm LJFL) and ‘b’, and no evidence was found of interaction between the two factors (attractor and size class). Although there was no significant difference between the total length-frequency distributions of swordfish caught with light-sticks and electralume attractors, significant differences were found for fish smaller than 125 cm LJFL, with electralume catches consisting of smaller swordfish than those of gear using light-sticks.
- Global-scale environmental niche and habitat of blue shark (Prionace glauca) by size and sex: a pivotal step to improving stock managementPublication . Druon, Jean-Noël; Campana, Steven; Vandeperre, Frederic; Hazin, Fábio H. V.; Bowlby, Heather; Coelho, Rui; Queiroz, Nuno; Serena, Fabrizio; Abascal, Francisco; Damalas, Dimitrios; Musyl, Michael; Lopez, Jon; Block, Barbara; Afonso, Pedro; Dewar, Heidi; Sabarros, Philippe S.; Finucci, Brittany; Zanzi, Antonella; Bach, Pascal; Senina, Inna; Garibaldi, Fulvio; Sims, David W.; Navarro, Joan; Cermeño, Pablo; Leone, Agostino; Diez, Guzmán; Zapiain, María Teresa Carreón; Deflorio, Michele; Romanov, Evgeny V.; Jung, Armelle; Lapinski, Matthieu; Francis, Malcolm P.; Hazin, Humberto; Travassos, PauloBlue shark (Prionace glauca) is amongst the most abundant shark species in international trade, however this highly migratory species has little effective management and the need for spatio-temporal strategies increases, possibly involving the most vulnerable stage or sex classes. We combined 265,595 blue shark observations (capture or satellite tag) with environmental data to present the first global-scale analysis of species' habitat preferences for five size and sex classes (small juveniles, large juvenile males and females, adult males and females). We leveraged the understanding of blue shark biotic environmental associations to develop two indicators of foraging location: productivity fronts in mesotrophic areas and mesopelagic micronekton in oligotrophic environments. Temperature (at surface and mixed layer depth plus 100 m) and sea surface height anomaly were used to exclude unsuitable abiotic environments. To capture the horizontal and vertical extent of thermal habitat for the blue shark, we defined the temperature niche relative to both sea surface temperature (SST) and the temperature 100 m below the mixed layer depth (Tmld+100). We show that the lifetime foraging niche incorporates highly diverse biotic and abiotic conditions: the blue shark tends to shift from mesotrophic and temperate surface waters during juvenile stages to more oligotrophic and warm surface waters for adults. However, low productivity limits all classes of blue shark habitat in the tropical western North Atlantic, and both low productivity and warm temperatures limit habitat in most of the equatorial Indian Ocean (except for the adult males) and tropical eastern Pacific. Large females tend to have greater habitat overlap with small juveniles than large males, more defined by temperature than productivity preferences. In particular, large juvenile females tend to extend their range into higher latitudes than large males, likely due to greater tolerance to relatively cold waters. Large juvenile and adult females also seem to avoid areas with intermediate SST (similar to 21.7-24.0 degrees C), resulting in separation from large males mostly in the tropical and temperate latitudes in the cold and warm seasons, respectively. The habitat requirements of sensitive size- and sex-specific stages to blue shark population dynamics are essential in management to improve conservation of this near-threatened species.
- Habitat use and migrations of shortfin mako in the atlantic using satellite telemetryPublication . Santos, Catarina C.; Domingo, Andrés; Carlson, John; Natanson, Lisa J.; Cortés, Enric; Miller, Philip; Hazin, Fábio H. V.; Travassos, Paulo; Mas, Federico; Coelho, RuiThis paper provides an update of the study on habitat use for shortfin mako, developed within the ICCAT Shark Research and Data Collection Program (SRDCP). Currently, all phase 1 (2015-2016) tags (23 tags: 9 miniPATs and 14 sPAT) and 11 tags from phase 2 (2016-2018) have been deployed by observers on Portuguese, Uruguayan, Brazilian and US vessels in the temperate NE and NW, Equatorial and SW Atlantic. Data from 32 tags/specimens is available and a total of 1260 tracking days have been recorded. Results showed shortfin makos moved in multiple directions, travelling considerable distances. Shortfin mako sharks spent most of their time above the thermocline (0-90 m), between 18 and 22 °C. The main plan for the next phase of the project is to continue the tag deployment during 2018 in several regions of the Atlantic.
- Morphological analysis and description of the ovaries of female silky sharks, Carcharhinus falciformis (Müller & Henle, 1839)Publication . Rego, Mariana G.; Hazin, Fábio H. V.; Evencio Neto, Joaquim; Oliveira, P. G. V.; Soares, Maria Goretti; Torres, Keilla Regina L. S.; Lana, Fernanda O.; Roque, Pollyana C. G.; Santos, Natalia L.; Coelho, RuiThis work aims to study the female reproductive tract of silky sharks, Carcharhinus falciformis, captured in the South and Equatorial Atlantic Ocean. Samples were collected between January 2008 and March 2010 through oceanic commercial vessels that targeted tuna and swordfish, with a total of 17 females collected. The methodologies followed for analyzing the ovaries of those females included both macroscopic and histological analysis. Macroscopically, it was possible to determine that the ovaries on these sharks is suspended by mesenteries in the anterior section of the body cavity, heavily irrigated by blood vessels, and contains a wide range of oocytes. Ovaries were found in three distinct maturational stages: Stage I (Immature), Stage II (Maturing) and Stage III (Mature). Immature ovaries were small, with widths ranging from 1.0 to 3.1 cm, and had a gelatinous or granulose internal structure; maturing ovaries were slightly larger, ranging in width between 5.2 and 6.0 cm; mature ovaries ranged in width between 6.5 and 7.8 cm, and had a more rounded shape and the presence of large and well developed oocytes. Under microscopic examination, it was observed that the ovaries were covered with simple epithelial tissue during the early development stages and a simple cubic epithelium in the final stages of maturation. During the initial maturation stages the epigonal organ was not differentiated from the ovary. In mature specimens, the ovary showed a simple cubic epithelium and just below this epithelium there was a layer of dense connective tissue and muscle with the presence of vitellogenic oocytes and fat cells. A thin yolk membrane enclosing the oocytes was also evident. Finally, it was possible to distinguish a zona pellucida, separating the oocytes from the follicle wall and a basal lamina between the granular layers and the teak layer.
- Post-release mortality of shortfin mako in the Atlantic using satellite telemetry: preliminary resultsPublication . Domingo, Andrés; Casaca Santos, Catarina; Carlson, John; Natanson, Lisa; Cortés, Enric; Mas, Federico; Miller, Philip; Hazin, Fábio H. V.; Travassos, Paulo; Coelho, RuiThis paper provides an update of the study on post-release mortality of the shortfin mako, Isurus oxyrinchus developed within the ICCAT Shark Research and Data Collection Program (SRDCP). Up to date, 34 tags (14 sPATs and 20 miniPATs) have been deployed by observers on Brazilian, Portuguese, Uruguayan, and US vessels in the temperate NE and NW, Equatorial and SW Atlantic. Data from 28 out of 34 tagged specimens could be used to obtain preliminary information regarding post-release mortality, resulting in a total of 7 mortality and 21 survival events.
- Preliminary results from project MAST/AM-advanced tracking and telemetry methodologies to study marine animalsPublication . Oliveira, P.; Silvestre, C.; Morgado, M.; Erzini, Karim; Bentes, L.; Afonso, A.; Hazin, Fábio H. V.; Block, B.This paper proposes advanced methodologies for the study of tagged marine animals, resorting to telemetry techniques. The robotic tools to be developed and operated will be able to track the acoustic signals emitted by the animals, based on range and depth data acquired with ultra-short baseline positioning (USBL) systems aided Inertial Navigation Systems (INS). The USBL is composed of an array of hydrophones with a pre-specified structure and the INS is based on the numerically integrated measurements from triads of low cost accelerometers, rate-gyroscopes, and magnetometers, complemented with data from depth cells. The preliminary design and implementation phases will be described and the results obtained to validate the proposed approach will be presented. Finally, the next development and validation phases will be briefly outlined.
- Regional movements of the tiger shark, Galeocerdo cuvier, off northeastern Brazil: inferences regarding shark attack hazardPublication . Hazin, Fábio H. V.; Afonso, Rosa Marina; De Castilho, Pedro C.; Ferreira, Luciana C.; Rocha, Bruno C. L. M.An abnormally high shark attack rate verified off Recife could be related to migratory behavior of tiger sharks. This situation started after the construction of the Suape port to the south of Recife. A previous study suggested that attacking sharks could be following northward currents and that they were being attracted shoreward by approaching vessels. In this scenario, such northward movement pattern could imply a higher probability of sharks accessing the littoral area of Recife after leaving Suape. Pop-up satellite archival taus were deployed on five tiger sharks caught off Recife to assess their movement patterns off northeastern Brazil. All tags transmitted from northward latitudes after 7-74 days of freedom. The shorter, soak distance between deployment and pop-up locations ranged between 33-209 km and implied minimum average speeds of 0.02-0.98 km.h(-1). Both pop-up locations and depth data suggest that tiger shark movements were conducted mostly over the continental shelf. The smaller sharks moved to deeper waters within 24 hours after releasing, but they assumed a shallower (< 50 m) vertical distribution for most of the monitoring period. While presenting the first data on tiger shark movements in the South Atlantic, this study also adds new information for the reasoning of the high shark attack rate verified in this region,
- Reproductive aspects of the oceanic whitetip shark, Carcharhinus longimanus (Elasmobranchii: Carcharhinidae), in the equatorial and southwestern Atlantic OceanPublication . Tambourgi, Mirna Regina dos Santos; Hazin, Fábio H. V.; Oliveira, Paulo G. V.; Coelho, Rui; Burgess, George; Roque, Pollyana C. G.The present study sought to study the reproductive biology of the oceanic whitetip shark, Carcharhinus longimanus, in the equatorial and southwestern Atlantic Ocean. A total of 234 specimens were collected as bycatch during pelagic longline fisheries targeting tunas and swordfish, between December 2003 and December 2010. The fishing area was located between latitudes 10N and 35S and longitudes 3E and 40W. Of the 234 individuals sampled, 118 were females (with sizes ranging from 81 to 227 cm TL, total length) and 116 males (ranging from 80 to 242 cm TL). The reproductive stages of the females were classed as immature, mature, preovulatory and pregnant, while males were divided into immature, maturing and mature. The size at maturity for females was estimated at 170.0 cm TL, while that for males was between 170.0 and 190.0 cm TL. Ovarian fecundity ranged from 1 to 10 follicles and uterine fecundity from 1 to 10 embryos. The reproductive cycle of this species is most likely biennial, with parturition occurring once every two years.