Age and growth of the smooth hammerhead shark, Sphyrna zygaena, in the Eastern Equatorial Atlantic Ocean, using vertebral sections

The smooth hammerhead shark Sphyrna zygaena (Sphyrnidae) is regularly caught as bycatch in pelagic longline fisheries, but is one of the least studied of all pelagic sharks. Recently, ICCAT (International Commission for the Conservation of Atlantic Tunas) issued recommendations underlining the need for more studies on the life history parameters of this and other pelagic shark species. To this end, the age and growth of S. zygaena were studied in the Eastern Equatorial Atlantic Ocean, in an area where growth parameters were not yet available for this species. Data from 139 specimens, caught between June and September 2009, ranging in size from 136 to 233 cm fork length (FL), were analysed. Preliminary trials were carried out to assess the most efficient growth band enhancement technique. These indicated that sectioning the vertebrae into 500 μm sections followed by staining with crystal violet produced the best results. Growth models were fitted using the traditional von Bertalanffy growth equation and a modification of this equation using a known size at birth. Growth models were compared using the Akaike information criterion (AIC). The von Bertalanffy growth equation seemed to be the most adequate model to describe growth in this species, with resulting growth parameters of L inf = 272 cm FL, k = 0.06 year for males and L inf = 285 cm FL, k = 0.07 year for females. In the first four years of life, S. zygaena grows 25 cm per year on average, but its growth slows down in later life. Future stock assessment models should incorporate these age and growth parameters for species management and conservation.info:eu-repo/semantics/publishedVersio

Record of partial albino in the scalloped hammerhead Sphyrna lewini (Carcharhiniformes, Sphyrnidae) in the Mexican Pacific Ocean: Registro de albinismo parcial en el martillo común Sphyrna lewini (Carcharhiniformes, Sphyrnidae) en el océano Pacífico mexicano

This study reports the capture of a partial albino scalloped hammerhead Sphyrna lewini in Puerto Madero, Chiapas, Mexico. The specimen was a neonate female that measured 491 mm total length and had a total weight of 800 g. This is the first report of an albino scalloped hammerhead Sphyrna lewini in the Pacific Ocean and the second in the world. The presence of albinism could be the result of multifactorial events, although anthropogenic stressors such as excessive fishing pressure and marine pollution might be involved

Characteristics of population dynamics of Lutjanus guttatus (Pisces: Lutjanidae) in Bufadero Bay, Michoacán, Mexico

Analysis of scales of Lutjanus guttatus (Steindachner, 1869) allowed the identification of three growth rings. Similar data were obtained with kernel density method. Values of the von Bertalanffys growth equation are: L? = 96.60 cm, W? = 7,508 g, K = 0.22 years-1 and to = -0.10 years. Maximum values of the condition factor occur during February and June and were preceded by two months of high values of the gastric repletion index. Maximum reproductive period was during April and August. Recruitment periods were from November to January and April to June. The recruitment length is 16 cm. The highest values of the hepatosomatic index are during December to June and showed an inversely proportional relation to the gonadosomatic index. First sexual maturity length is 30.63 cm and its longevity of 13.5 years. Forty one percent of L. guttatus individuals captured in Bufadero Bay are sexually immature, therefore we suggest a minimum capture size of 45 cm (age 2.5 years) and a closed season from August to September

Age and growth of the scalloped hammerhead shark, Sphyrna lewini (Griffith & Smith, 1834) from the Southern coast of Sinaloa, México

Age and growth for the scalloped hammerhead shark (Sphyrna lewini) were determined from opaque bands (OBs) on postcephalic vertebrae from 109 organisms (44 females, 52 cm to 276 cm total length (TL) and 65 males, 47 cm to 245 cm TL) obtained bimonthly from commercial fisheries off the southern coast of Sinaloa state (23º45´25´´N and 106º05´15´´W to 21º52´N and 105º54´W) from January 2003 to February 2005. The Bowker test of symmetry and the Index of Average Percent Error, suggest that this ageing method represents an unbiased and precise age assessment. Results show that immediately after birth (in summer), the first OB was formed and in the next winter showed the second OB. Later it was observed that two OBs were formed each year, one during summer and the other during winter, influenced by the sea surface temperature (SST). Based on the comparison of five back-calculation methods, the best methods were FraserLee. The parameters of the von Bertalanffy growth function were, for females: L? = 376 cm, K = 0.1 year-1, t0 = -1.16 years, b = 3 and W? = 222 kg; for males: L? = 364 cm, K = 0.123 year-1, t0 = 1.18 years, b = 3 and W? = 193 kg. The standard index growth (?´) was 4.2 (s = 0.1). According to these results the largest sharks observed, a female of 280 cm TL would be 12.5 years old and a male of 281cm TL would be 11 years old

A new record of bony fish prey for the genus Isistius (Chondrichthyes: Dalatiidae) in a coastal zone of southeastern Mexico

The first report of bite wounds from cookiecutter shark in a specimen of cobia in the Southern Gulf of Mexico is described. The specimen was captured by artisanal fishery in the coastal zone of Tabasco, Mexico. It presented three bite wounds with 25 to 26 teeth marks per wound, major axis interval between 3.7 and 4.7 cm and all areas of less than 10 cm2. This is new record of a bony fish as prey of genus Isistius maybe of I. brasiliensis in coastal waters over the continental shelf, in the Southern Gulf of Mexico

Age and growth of the smooth hammerhead, Sphyrna zygaena, in the Atlantic Ocean: comparison with other hammerhead species

The smooth hammerhead Sphyrna zygaena (Sphyrnidae) is a pelagic shark occasionally caught as bycatch in pelagic longline fisheries, but is one of the least studied of all pelagic sharks. Age and growth of S. zygaena was studied along a wide Atlantic region covering both the northern and southern hemispheres. Data from 304 specimens, caught between October 2009 and September 2014, ranging in size from 126 to 253 cm fork length (FL), were analysed. Growth models were fitted using the three-parameter von Bertalanffy growth function (VBGF) re-parameterized to calculate L0 (size at birth). Growth models were fitted to the sample data and data from several back-calculation models. The model fit to the quadratic modified Dahl-Lea back-calculated data seems to be the most appropriate to describe growth in this species, with resulting growth parameters of Linf = 285 cm FL, k = 0.09 year−1 for males and Linf = 293 cm FL, k = 0.09 year−1 for females. Compared with other species of the same genus, estimated growth coefficients for S. zygaena seem to fall in the low to middle range. Although further work is still needed, this study adds to knowledge of the vital life-history parameters of smooth hammerheads in the Atlantic Ocean, which can be used in the management and conservation of this species.Programa Operacional Potencial Humano: IF/00253/2014info:eu-repo/semantics/publishedVersio

Age and growth for the scalloped hammerhead shark, sphyrna lewini (griffith and smith, 1834) along the central pacific coast of mexico

The age and growth of the scalloped hammerhead shark, Sphyrna lewini (Griffith and Smith, 1834) were estimated from rings on the vertebral centrum in 101 individuals (51 females and 50 males) from 260 organisms obtained from commercial fisheries off the coast of Michoacán, Mexico (18º10'N, 103º10'W). Results show that immediately after birth, a first ring is formed. Later we observed that two rings are formed each year, one between June and July and the other between November and December. The parameters of the von Bertalanffy growth function were, for females, L∞ = 353.3 cm, K = 0.156 cm yr–1, t0 = –0.633 years, b = 2.8 and W∞ = 269.92 kg; and, for males, L∞ = 336.4 cm, K = 0.131 cm yr–1, t0 = –1.09 years, b = 2.87 and W∞ = 187 kg. According to these results, a female 335.6- cm-long would be 18.6 years old and a male of 244.3 cm would be 8.8 years old

Primeiro registro de albinismo na raia redonda anã, Urotrygon nana (Urotrygonidae: Elasmobranchii), no Pacífico Oriental

El albinismo es una condición genética en la cual la proteína melánica está ausente o no es funcional y ocasionalmente ha sido reportado en el grupo de los condrictios. En este trabajo se describe el albinismo total en una raya redonda enana, Urotrygon nana, hembra madura de 81 mm del ancho de disco y con un peso de 18.42 g, fue capturada por medio de arrastre de fondo a una profundidad de 40 m frente a Puerto Madero, Chiapas, Golfo de Tehuantepec, Pacífico oriental (14° 31ʼ 6ʼʼ N - 92° 26ʼ 75ʼʼ W). Se cuantificaron las características morfométricas del ejemplar albino y se compararon con las de un espécimen normal del mismo sexo. Este trabajo representa el primer registro de esta anormalidad en la familia Urotrygonidae.Albinism is a genetic condition in which the melanin pigment protein is either absent or nonfunctional and has occasionally been reported in chondrichthyes. Total albinism in an 18.42 g female adult dwarf stingray, Urotrygon nana, with an 81 mm disc width is described in this paper. The subject was caught using bottom trawl methods 40 m deep off Puerto Madero, Chiapas, Gulf of Tehuantepec, eastern Pacific (14° 31ʼ 6ʼʼ N - 92° 26ʼ 75ʼʼ W). The albino morphometric characteristics were compared with those of normal specimens of the same sex. This paper represents the first record of this abnormality in the family Urotrygonidae.O albinismo é uma condição genética na qual a proteína melânica está ausente ou não é funcional e, ocasionalmente, tem sido reportado no grupo dos condrictes. Neste trabalho se descreve o albinismo total em uma raia redonda anã, Urotrygon nana, fêmea madura de 81mm de largura de disco e com um peso de 18.42g, que foi capturada por meio de arrasto de fundo a uma profundidade de 40m em frente ao Puerto Madero, Chiapas, Golfo de Tehuantepec, Pacífico oriental (14° 31ʼ 6ʼʼ N - 92° 26ʼ 75ʼʼ W). Foram quantificadas as características morfométricas do exemplar albino e comparadas com as de um espécimen normal do mesmo sexo. Este trabalho representa o primeiro registro desta anormalidade na família Urotrygonidae