Francisco M. Santana

Age and growth of the blue shark Prionace glauca (Linnaeus, 1758) off northeastern Brazil

Between 1992 and 2000, 681 blue sharks, Prionace glauca(173.8–310 cm total length, TL) were collected off northeastern Brazil (Brazilian EEZ). Vertebral sections of 156 males (173.8–310 cm TL) and 80 females (185.5–283 cm TL) were analysed. The index of average percentage error (IAPE) ranged from 0 to 3.1% for 3–12 growth rings (GRs). Mean marginal increment (MI) decreased from November to January without, however, conclusively confirm the annual pattern of deposition. Growth parameters were derived using the von Bertalanffy growth function (VBGF), the Richards function and the Schnute function. VBGF was that which best fit the data. Parameters derived from back-calculated lengths, K = 0.157, L∞ = 352.1 cm and t0 =− 1.01 year, were considered to best describe growth. First maturity sizes of 225 cm for males and 228 cm for females corresponded to 5-GRs individuals. A 310-cm male had 12 GRs which was the highest number in the entire sample. Growth rates of 33.9 cm per GR were estimated from birth to the first band corresponding to 60.2% of size at birth, which is 56.4 cm. Adult males were 90.5% of the entire male sample and, adult females corresponded to 79.6% of the sample of females. The male sample was composed of individuals from 3 to >11 GRs and females were 3 to 10 GRs. Males were larger (with higher number of GRs) and outnumbered females in the overall sample, as commonly occurs in catches worldwide. Despite the hypothesis of differential growth by sex, postulated by several authors, the present study demonstrated that growth curves did not differ significantly, even considering significant vertebral radius (VR)–TL regressions for males and females. Higher growth rates were found in the southern Hemisphere, leading to significant differences in VBGF when compared to other areas. Discards and unreported catches are of great concern for conservation of this important apex predator.

A better way forward for Brazil's fisheries.

In December 2014, the Brazilian Minister of the Environment released the new national red lists enumerating 2113 plants and 1173 animals threatened with extinction ([ 1 ][1]). Of the 475 aquatic species on the list, 83 are commercially exploited by fisheries, mainly as by-catch. The industrial

A critical appraisal of marginal increment analysis for assessing temporal periodicity in band formation among tropical sharks

Marginal increment ratio (MIR) analyses were conducted as part of age and growth studies on three coastal/semi-oceanic species, the smalltail shark, Carcharhinus porosus, daggernose shark, Isogomphodon oxyrhynchus and the night shark C. signatus, and two ubiquitous oceanic species, blue shark, Prionace glauca, and whitetip shark, C. longimanus, collected in equatorial areas off Brazil with the aim of establishing the interspecific temporal nature of vertebral band formation. Monthly variations in marginal bands were analyzed using mean MIR on the entire sample as the standard method for all species. Reasons for the inconclusive results regarding these species are critically appraised with respect to three main sources of bias that are associated with marginal increment analysis (MIA). Bias due to insufficient sample sizes may have hampered the analysis for I. oxyrhynchus and C. longimanus due to movements from shallow waters to seamounts for the former species and to extensive migrations for the latter. Bias due to data collection over too long a period is thought to have influenced monthly mean MIR for C. porosus and P. glauca. For the latter, individuals from different age groups lay down rings at different times, making band deposition inconsistent between individuals. Finally, bias due to births occurring over too long a period was the prevalent cause for confounding MIR values among I. oxyrhynchus and C. signatus species, whose birth period lasts several months and leads to different ages within the same cohort. Other approaches used for MIA in C. signatus and P.␣glauca led to distinct times of band formation by age-groups when compared to MIR applied on the entire sample. For the daggernose shark, delays in events related to the reproductive cycle from one year to the next were also found to confound MIR. Requirements for the use of MIR implying a band width that displays a sinusoidal cycle when temporally plotted (month or season) were not fulfilled for any of these species. The method has been of little utility for detecting the periodicity of band deposition among sharks from the tropics. This emphasizes the need for supplying information on the temporal periodicity of pair deposition based on other methods.

Age and growth of the daggernose shark, Isogomphodon oxyrhynchus, from northern Brazil

Age and growth of the daggernose shark, Isogomphodon oxyrhynchus, from northern Brazil were deter- mined from 105 vertebral sections stained with alizarin red-S representing 46 males, 52 females and 7 specimens of unknown sex (58.4 to 141 cm-TL) and verified with length-frequency analysis of 1135 specimens (632 females and 503 males, 58-160 cm ). Marginal increments did not show significant differences throughout the year, and it was assumed that one band is formed annually. Different tests provided varying results for growth curve comparisons between sexes; the curves were similar, despite biological differences. von Bertalanffy growth parameters estimated from back-calculated mean lengths, observed mean lengths-at-age and length-frequency analysis were of the same magnitude. Parameters generated from observed length-at-age were chosen for describing growth for the species: L∞ 171.4 cm, k 0.12 year -1 and t0 -2.612 years. The largest female aged from vertebrae was 12 years old, whereas the largest male was aged at 7 years. Neonates, ~42.3 cm, showed one band in the vertebrae, formed at birth, or soon thereafter. Males are mature at 103 cm or 5-6 years and females at 115 cm or 6-7 years. Resumo. A idade e o crescimento do cacao quati, Isogomphodon oxyrhynchus, do norte do Brasil foi determinada usando 105 vertebras seccionadas e coradas com alizarina vermelha-S de 46 machos, 52 femeas e 7 exemplares de sexo indeterminado (58,4-141 cm-CT). Analise de distribuicao de frequencia de comprimentos de 1135 individuos (632 femeas e 503 machos, 58-160 cm) foi utilizada como metodo de verificacao. Os incrementos marginais nao mostraram diferencas significativas ao longo do ano, assumindo-se que uma banda e formada anualmente. Com diferentes testes, usados para comparar curvas de crescimento entre os sexos, obteve-se resultados conflitantes; o crescimento foi considerado identico entre os sexos, apesar das diferencas biologicas entre machos e femeas. Os parâmetros de von Bertalanffy estimados do retrocalculo, comprimentos medios observados e da analise de compri- mentos foram semelhantes, tendo sido escolhidos para descrever o crescimento da especie: L∞ 171,4 cm; k 0,12 year -1 e t0 -2,612 years. A maior femea cuja idade foi estimada pelas vertebras tinha 12 anos enquanto o maior macho tinha 7 anos. Recem-nascidos de 42,3 cm apresentavam uma banda nas vertebras, formada ao nascer, ou logo depois do nascimento. Machos estao maduros em 103 cm ou 5-6 anos e femeas em 115 cm ou 6-7 anos.

Extraordinary growth in tiger sharks Galeocerdo cuvier from the South Atlantic Ocean.

Two tagged-and-recaptured tiger sharks Galeocerdo cuvier, measuring 172 and 304 cm total length (L(T) ) and at age 0.75 and 3.50 years, exhibited unmatched growth rates of 118.4 and 55.5 cm year(-1), respectively. The larger fish was nearly mature, indicating that G. cuvier off Brazil could mature considerably earlier than conspecifics from other regions.

Age, Growth and Spatial Distribution of the Life Stages of the Shortfin Mako, Isurus oxyrinchus (Rafinesque, 1810) Caught in the Western and Central Atlantic

The shortfin mako (Isurus oxyrinchus) is a highly migratory pelagic shark that preferentially inhabits oceanic regions in practically all oceans. The wide distribution range of this species renders it susceptible to coastal and oceanic fishing operations. The International Union for Conservation of Nature (IUCN) and the International Commission for the Conservation of Atlantic Tunas (ICCAT) consider this species to be highly vulnerable, especially due to its biological parameters, which are different from those of other sharks that occupy the same niche (e.g., Prionace glauca). Consequently, considerable declines in abundance have been detected over various parts of its range, most of which are linked to oceanic longline fishing. The species has conflicting life history parameters in studies conducted in the last 30 years, especially with regard to age and growth. The main discrepancies regard the interpretation of the periodicity of the deposition of band pairs (BPs) on vertebrae and the possibility of ontogenetic variations in growth. Shortfin mako sharks (n = 1325) were sampled by onboard observers of the Brazilian chartered pelagic longline fleet based in northeast Brazil from 2005 to 2011. Lengths were 79 to 250 and 73 to 296 cm (fork length, FL) for males and females, respectively, with a statistically significant difference in size between sexes and differences in the proportion of individuals in each size class. The onboard observers collected a subsample of vertebrae (n = 467), only 234 of which were suitable for analyses. Reliability between readings was satisfactory. However, it was not possible to validate periodicity in the formation of age bands in the sample. Thus, the von Bertalanffy growth function was used to calculate growth rates for the species through the interpretation of BPs in different scenarios: one BP per year (s1), two BPs per year (s2) and two BPs per year until five years of life (s3). Growth parameters varied for both females (Linf = 309.7[s3] to 441.6[s1]; k = 0.04[s1] to 0.13[s3]; t0 = -7.08[s1] and -3.27[s3]) and males (Linf = 291.5[s3] to 340.2[s1]; k = 0.04[s1] to 0.13[s3]; t0 = -7.08[s1] and -3.27[s3]). To advance the understanding of the use of habitat, the first analysis of the spatial distribution of the life stages of the shortfin mako sharks caught by commercial longline fishing operations in the South Atlantic was performed. The findings indicate that the portion of the population exploited by the fleets is predominantly juvenile and future actions should take the following issues into account: improvements in the efficiency of data collection procedures, the reestablishment of the onboard observer program, emergency investments in studies that can contribute to a better understanding of habitat use and life history theory.

Age and growth of the endemic Xingu River stingray Potamotrygon leopoldi validated using fluorescent dyes: AGE AND GROWTH OF THE XINGU RIVER P. LEOPOLDI

Between 2003 and 2005, vertebrae of 151 Xingu River Potamotrygon leopoldi (Potamotrygonidae) (75 males and 76 females) were analysed to derive a growth curve for this species. The disc width (WD ) was significantly different between sexes, with females measuring 149-700 mm WD and males 109-500 mm WD . The average percentage error for vertebrae readings of the whole sample was 2·7%. The marginal increment ratio (RMI ) showed an increasing trend with the highest value in November, decreasing from December on. The majority of vertebrae displaying RMI zero, occurred in September, but the annual periodicity of ring deposition throughout the year was not conclusive. Tetracycline (TCN) injected specimens were held in captivity for 13 months and displayed a fluorescent mark in vertebrae confirming a yearly periodicity of band pair formation with the translucent ring deposited in September-October. The Akaike information criterion (AIC) showed that, among the seven models considered, the best fit was obtained for the von Bertalanffy modified with W0 (where W0 = WD at birth) for both sexes. Growth parameters for females were: W0 = 149 mm; W∞ = 763·06 mm; k = 0·12 year- 1 , whereas for males: W0 = 109 mm; W∞ = 536·4 and k = 0·22 year-1 . Maximal ages were 7·2 years in males and 14·3 years in females. The species shows sexual dimorphism expressed in the growth pattern, size at maturity, longevity and asymptotic sizes. Concern for sustainability is raised due to the construction of the Belo Monte Hydroelectric Power Plant (2015 and 2016) in the State of Pará causing changes to the habitat of this species, which is endemic to the Xingu River and two of its tributaries.

Age, growth and mortality of white grunt caught in Pernambuco State, Brazil

The aim of the present study was to measure the primary growth parameters and to estimate the mortality of the white grunt Haemulon plumierii in the state of Pernambuco, Brazil. Sagittal otoliths were collected monthly from May 2013 to April 2014 from three different commercial fishing landings along the coast of Pernambuco. A total of 333 individuals measuring 10.5 to 32.2 cm total length were caught. The total length distributions were different between locations. The weight-length relationships and the von Bertalanffy equations were statistically different between the three fishing sites. The weight-length relationship indicated negative allometric growth, therefore the von Bertalanffy equation for pooled sexes was TLt = 31.1[1-e-0.1 (t +4.57)]. The maximum observed age was 21 years and the mortality rate was 0.21 year-1. The conducted analysis indicates a species with long life cycle and slow growth. Small reef fish with slow movement, such as the white grunt, are susceptible to fishing efforts, environmental factors and degradation, which affect growth and mortality. Therefore, we suggest an assessment of the status of the stock.

Age and growth of the midwater crocodile shark Pseudocarcharias kamoharai

Age and growth were analysed on the basis of 372 vertebrae from specimens of the crocodile shark Pseudocarcharias kamoharai (66·0-122·0 cm, total length, LT ) collected in the south-western Atlantic Ocean. Centrum edge analysis suggested the first four months of the year as the period of band completion, leading to acceptance of free-living bands as annual. A pre-birth ring is formed in embryos >31·0 cm LT , whereas the birthmark is deposited in newborns of 46·1 ± 1·1 cm LT (mean ± s.d.). Growth was parameterized using seven models and the AIC was used for selection of the most plausible model. The von Bertalanffy growth model received the greatest support from the data, providing the following growth parameters for combined sexes: L∞ = 129·2 cm, k = 0·137 year(-1) and t0 = -3·9 years. No significant differences were detected in growth by sex, but significant differences in age composition by sex were found in the sample. Overall age ranged from 2 to >13 years in females and from 1 to 8 years in males. Males achieved first maturity at 3·1 years and females at 5·1 years, with pregnancy appearing at 4·8 years. Similar to other lamnoid species, P. kamoharai is relatively fast growing.