Leonel Serrano Gordo

Growth and reproduction of horse mackerel, Trachurus trachurus (carangidae)

There is a broad knowledge of the growth andreproduction of Trachurus trachurus,although important gaps still exist. Horsemackerel are a long-lived species, reaching upto 40 years of age. They have isometric growth,although the alometric parameter b mayvary throughout the year and in relation tolatitude. Growth to age 3 is rapid compared toslower growth later in life. Phenomena ofdensity dependent growth have been observed inthe northeast Atlantic. Horse mackerel are anasynchronous species. The following stages ofatresia have been validated in horse mackerel:alpha, beta, and delta. The transition infemales from the spawning state to postspawning is very fast. The spawning fraction inhorse mackerel is estimated to be between 8.3%and 20.9%. Horse mackerel have a long spawningseason (up to 8 months), which varies accordingto geography. Length at first maturity isbetween 16 and 25 cm, most commonly around21 cm. Males mature at a slightly smallerlength than females. The age at first maturityfor females has been estimated to range from 2to 4 years, depending on the geography. Batchfecundity has been estimated to range between172–209 oocytes per gram-female-weight. Femalespawning lasts between 65 and 94 days. Anindividual female can release from 5 to 16batches during the spawning period. Theestimated potential annual relative fecundityranges from 1040 to 3280 oocytes pergram-female-weight.

Molecular barcoding of north-east Atlantic deep-water sharks: species identification and application to fisheries management and conservation

Two genera of elasmobranchii, Centrophorus and Centroscymnus, include species that represent the highest landings of deep-water sharks caught by fishing fleets operating in the north-east Atlantic. There are morphology-based identification problems among and within genera, and landings of processed shark products further prevent an objective assessment of these species. The present study is the first attempt to test the suitability of using a DNA barcode approach to discriminate accurately among the four most important commercial deep-water shark species: Centrophorus squamosus, Centrophorus granulosus, Centroscymnus coelolepis and, recently discovered in Portuguese ports, Centroscymnus owstoni. Sequence analyses of the mitochondrial DNA cytochrome c oxidase subunit I (COI) gene revealed low levels of haplotypic and genetic diversities. Higher levels of inter-specific relative to intra-specific divergences allowed discrimination among species, which form reciprocally monophyletic clades. Inclusion of published COI sequences from other species within the same genera revealed haplotype sharing among species, which calls into question the current taxonomy and accuracy of fisheries data available. Amplification of the COI gene coupled with MboI restriction digests was found to be a fast and inexpensive strategy to resolve within genera identification problems. Molecular barcoding constitutes a critical tool for the assessment and implementation of urgent management policies for this group of species.

The fish assemblage structure of a hydrologically altered coastal lagoon: the Óbidos lagoon (Portugal)

The fish assemblage of the Óbidos lagoon was studied between January 1993 and December 1994 based on beach seine catches. Forty-one species were identified, with Gobius niger, Syngnathus acus, Atherina boyeri, Dicentrarchus labrax, Liza aurata, Chelon labrosus and Symphodus bailloni the most common species. The community was dominated by the families Atherinidae, Mugilidae and Gobiidae, which is characteristic of temperate and tropical estuaries and coastal lagoons. Community ordination analysis outlined three major fish assemblages along a longitudinal environmental gradient, determined by salinity, sediment and turbidity. Euryhaline fish species, such as Lizaramada and Mugil cephalus, were particularly abundant in the upper part of the lagoon. The middle area was dominated by estuarine resident species, namely G. niger, A. boyeri, S. acus and S. bailloni, while in the lower part of the lagoon the fish assemblage was composed of inshore marine species. The seasonal pattern was mainly induced by the annual cycle of resident species and by the migration of juveniles moving between coastal areas and the lagoon. If human activities related to keeping the mouth of the lagoon open to the sea ceased, the nursery function of this estuarine system would be affected, with a dominance of euryhaline fish species expected throughout the lagoon.The fish assemblage of the Óbidos lagoon was studied between January 1993 and December 1994 based on beach seine catches. Forty-one species were identified, with Gobius niger, Syngnathus acus, Atherina boyeri, Dicentrarchus labrax, Liza aurata, Chelon labrosus and Symphodus bailloni the most common species. The community was dominated by the families Atherinidae, Mugilidae and Gobiidae, which is characteristic of temperate and tropical estuaries and coastal lagoons. Community ordination analysis outlined three major fish assemblages along a longitudinal environmental gradient, determined by salinity, sediment and turbidity. Euryhaline fish species, such as Liza ramada and Mugil cephalus, were particularly abundant in the upper part of the lagoon. The middle area was dominated by estuarine resident species, namely G. niger, A. boyeri, S. acus and S. bailloni, while in the lower part of the lagoon the fish assemblage was composed of inshore marine species. The seasonal pattern was mainly induced by the annual cycle of resident species and by the migration of juveniles moving between coastal areas and the lagoon. If human activities related to keeping the mouth of the lagoon open to the sea ceased, the nursery function of this estuarine system would be affected, with a dominance of euryhaline fish species expected throughout the lagoon.

Reproductive biology and embryonic development of Centroscymnus coelolepis in Portuguese mainland waters

A total of 871 females (76-122 cm) and 86 males (68-100 cm) of Centroscymnus coelolepis caught in Portuguese mainland waters were examined for reproductive characteristics. One hermaphroditic individual of 95 cm was found. Males were few in numbers and dominated by immature specimens. Female length at first sexual maturity was 98.5 cm. Mean ovarian and uterine fecundity were 13.2 oocytes per female and 9.9 embryos per pregnant female, respectively. Total length of embryos with completely absorbed external yolk sacs ranged between 233 and 300 mm. Sex ratio (F/M) of embryos with completely absorbed external yolk sac was 0.9. All stages of reproduction were found during the 12-month sampling period. Results were compared with those from other regions. A hypothesis is formulated on the existence of several regional populations based on morphometric and reproductive parameters observed in different areas.

Observations on the reproductive cycle of the black scabbardfish ( Aphanopus carbo Lowe, 1839) in the NE Atlantic

Black scabbardfish is a deep-water species, common in the NE Atlantic at depths between 450 and 1300 m, currently exploited by some European countries. Between May 1998 and April 2000, specimens collected at three different locations in the NE Atlantic—NW of Scotland, Sesimbra (mainland Portugal) and Funchal (Madeira)—were analysed. The evolution of maturity of both sexes throughout the year was studied based on the macroscopic and microscopic analysis of the gonads. Specimens with the largest total length were found in Funchal, whereas the smallest size was recorded in the NW of Scotland. Neither spawners nor post-spawners were ever observed in NW of Scotland and Sesimbra. In Sesimbra, only a few individuals attained pre-spawning stage and most of the early developing females exhibited atresia in their ovaries. In Funchal, all the maturity stages were found; spawners occurred from September to December (females) and from August to December (males). Length of first maturity for females was estimated to be around 1000 mm. Two groups of spawners with different sizes were observed during the spawning period off Madeira.

Molecular barcoding of skates (Chondrichthyes: Rajidae) from the southern Northeast Atlantic

Serra‐Pereira, B., Moura, T., Griffiths, A. M., Gordo, L. S. & Figueiredo, I. (2010). Molecular barcoding of skates (Chondrichthyes: Rajidae) from the southern Northeast Atlantic. —Zoologica Scripta, 40, 76–84.

The use of caudal thorns for ageing Raja undulata from the Portuguese continental shelf, with comments on its reproductive cycle

The present study focuses on age estimation, with reproductive information contributing to the better understanding of the growth and the biology of Raja undulata. In the age and growth study, two calcified structures were used: caudal thorns and central vertebra. Results of readings showed that there were no significant differences in age estimates between the two structures. Both von Bertalanffy and Gompertz growth models were fitted to size-at-age data by sex and geographical area. No significant differences were found between sexes for the two models but significant differences were found between geographical areas (P = 0.05). The Gompertz growth function was selected as the best model to describe R. undulata growth because it presented the best fit and the most reasonable biological estimates. Reproductive analysis indicates one annual breeding season for R. undulata. The differences found in the estimates of length at first maturity between geographical areas (TL50% = 838 mm in Peniche and 762 mm in Algarve for females and TL50% = 781 mm in Peniche and 736 mm in Algarve for males), together with the regional differences found between growth parameters estimates (P = 0.05), may reflect the existence of different local populations of R. undulata on the Portuguese continental shelf.

Estimation of Risk Assessment of Some Heavy Metals Intake Through Black Scabbardfish (Aphanopus carbo) Consumption in Portugal

The intake of Cd, methyl-Hg, and Pb through consumption of black scabbardfish (BSF) (Aphanopus carbo) in Portugal as well as the associated probability of exceeding the respective provisional tolerable weekly intakes (PTWIs) was estimated. For this purpose, the contamination levels of heavy metals in this fish species were combined with constructed consumption scenarios or with a hypothesized consumption distribution. Whereas Cd and Pb posed no serious risk, the consumption of at least one portion of BSF per month as well as the hypothetical study in the Portuguese population produced nonnegligible probabilities of surpassing the PTWI for Me-Hg. Risk assessment for Portuguese consumers revealed a higher risk regarding Me-Hg, 1.19% and 1.81% with the plug-in (PI) and the tail estimation (TE) estimators, respectively. On the other hand, the risk for Cd and Pb was less than 1 in 100,000. TE was more realistic and accurate for Cd and Pb. Concerning Me-Hg, TE and PI estimators produced similar results. Furthermore, the limitations of a deterministic approach were shown.

Discriminating bluemouth, Helicolenus dactylopterus (Pisces: Sebastidae), stocks in Portuguese waters by means of otolith shape analysis

ana neves, vera sequeira, ines farias, ana rita vieira, rafaela paiva and leonel serrano gordo Faculdade de Ciencias da Universidade de Lisboa, Departamento de Biologia Animal & Centro de Oceanografia, Bloco C2, Campo Grande, 1749-016 Lisboa, Portugal, Unidade de Recursos Marinhos e Sustentabilidade, Instituto de Investigacao das Pescas e do Mar (IPIMAR–INRB), Avenida Brasilia, 1449–006 Lisboa, Portugal

The development of the oviducal gland in the Rajid thornback ray, Raja clavata

The reproductive processes of chondrichthyans are complex. Knowledge of the development and maturation of the oviducal gland is vital for understanding the reproductive biology of a species. This study represents the first contribution of this subject for skates. In the oviparous thornback ray, Raja clavata, oviducal gland development begins early in the developing stage with the formation of gland tubules and the distinct lamellae of each zone: club, papillary, baffle and terminal. Oviducal development is complete by the end of the developing stage when the storage and secretion of products is evident within the gland tubules of each zone. Periodic acid-Schiff and alcian blue histological staining showed that the secretory mucous cells of the club and papillary zones produce neutral and sulfated acid mucins. The last row of gland tubules of the papillary zone stains intensely for sulfated acid mucins. The baffle zone, which is responsible for the production of the egg capsule, represented 60–80% of the glandular zone of the oviducal gland. Sperm bundles were observed in the deeper recesses of the baffle zone during the maturation process, and during capsule extrusion, sperm were detected near the lumen. The terminal zone was composed of two types of gland tubules: serous (producing protein fibres) and mucous glands (producing sulfated acid mucins).