Size and Age at Maturity for Vermilion Snapper (Rhomboplites aurorubens) (Lutjanidae) in the South Atlantic Bight (original) (raw)
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ICES Journal of Marine Science, 2006
. Histological analysis invalidates macroscopically determined maturity ogives of the Kattegat cod (Gadus morhua) and suggests new proxies for estimating maturity status of individual fish. e ICES Journal of Marine Science, 63: 485e492. Assessment and management of fish populations currently rely on correct estimation of the spawning-stock biomass (SSB), which is based on accurate maturity ogives of the population. Although maturity ogives are usually calculated through macroscopic evaluation of the gonads, histology is generally considered to be more accurate. Here we show that the macroscopic analysis consistently overestimates the proportion of mature females for all age classes in Kattegat cod. The resulting bias showed minimum values for all age classes about a month before the spawning season. Consequently, estimation of the incidence of maturation in females several months before or after the spawning season can only be accurate using histological techniques. Further, the observed bias was used to reconstruct a historical data set of maturity ogives of Kattegat cod. The results showed that female spawning biomass (FSB) might have been overestimated by up to 35%. However, as histological analysis is considered a laborious procedure, proxies of maturity status were sought. It was indicated that the gonadosomatic and hepatosomatic indices may serve as robust proxies for discriminating mature females from immature, thus greatly enhancing the accuracy of the macroscopic maturity evaluation of cod gonads when histological analysis is lacking.
From May 2006 to February 2008, gonads of 215 sailfish caught in the western South Atlantic were examined. In Area 1 (7°N to 24°S/15.5° to 40°W) 153 specimens were examined, of which 95 were females ranging in LJFL from 114-210 cm, whereas the 58 males ranged from 104-185 cm. In Area 2 (22° to 27°S/39° to 47°W) 62 specimens were examined, of which 32 were females ranging in LJFL from 130-197 cm. The 30 males ranged from 133-176 cm LJFL. The sex ratio analysis indicated the predominance of females in almost all months in both areas. However, in September in Area 1 a significant difference was always noted on the expected proportion 1:1. In area 1, females with maturing stage ovaries were the majority and occurred in all sampled months. Immature females were more frequent in January and February. Females with ripe ovaries were practically absent, with only one specimen caught in November. In contrast, in Area 2 females with ripe or spent ovaries were frequently found from December to February. The gonad index analysis showed higher mean values (>2) in Area 2 from December and January. In comparison, Area 1 presented smaller mean values of gonad index (< 1.5) throughout the year. In this study, the size at first sexual maturity (L 50 ) of females based on ovarian macroscopic examination was equal a 154.93 cm LJFL. The results of the present study confirm the hypothesis that sailfish spawn in the southeast Brazilian coast (Area 1 of the present study) during the 1 st and 4 th quarters. However, the results are preliminary since the visual assessment of ovaries to determine the maturity stage is felt to be an imprecise indicator of reproductive condition. New studies based on histological analysis of gonads are needed, as well as additional research (including tagging experiments) is necessary to better understand the migration route after spawning. RÉSUMÉ Du mois de mai 2006 à février 2008, des gonades de 215 voiliers capturés dans l'Atlantique Sud-Ouest ont été examinées. Dans la zone 1 (7°N à 24°S/15,5° à 40°W), 153 spécimens ont été étudiés : 95 femelles, dont la taille allait de 114 à 210 cm LJFL, et 58 mâles dont la taille allait de 104 à 185 cm. Dans la zone 2 (22° à 27°S/39° à 47°W), 62 spécimens ont été étudiés : 32 femelles, dont la taille oscillait entre 130 et 197 cm LJFL, et 30 mâles dont la taille variait de 133 à 176 cm LJFL. L'analyse de sex-ratio indiquait la prédominance des femelles pendant presque tous les mois de l'année dans les deux zones. Cependant, en septembre, dans la zone 1, une différence significative a toujours été notée dans la proportion attendue 1:1. Dans la zone 1, les femelles avec des ovaires en phase de maturation représentaient la majorité et étaient présentes dans tous les mois échantillonnés. Les femelles immatures étaient les plus fréquentes en janvier et février. Les femelles avec des ovaires matures étaient pratiquement absentes, avec un seul spécimen capturé en novembre. En revanche, dans la zone 2 les femelles avec des ovaires matures ou vides étaient fréquentes de décembre à février. L'analyse de l'indice gonadique présentait des valeurs moyennes élevées (>2) dans la zone 2 de décembre à janvier. Par comparaison, la zone 1 présentait des valeurs moyennes plus faibles de l'indice gonadique (< 1,5) tout au long de l'année. Dans la présente étude, la taille à la première maturité sexuelle (L 50 ) des femelles, basée sur un examen macroscopique des ovaires, s'élevait à 154,93 cm LJFL. Les résultats de cette étude confirment l'hypothèse selon laquelle le voilier fraye sur la
Age, Growth, and Reproduction of Vermilion Snapper in the North-Central Gulf of Mexico
Transactions of The American Fisheries Society, 2018
Vermilion Snapper is a commonly harvested species of reef fish in the northern Gulf of Mexico (GOM). It supports both a large commercial and popular recreational fishery, however, knowledge of this fish's life history is limited spatially. Non-linear curve fitting was used to estimate growth parameters and Akaike information criteria (AIC) was used to determine relative model fit. The 2-parameter von Bertalanffy growth function provided the best model fit and lowest AIC score. Histological examination indicated that Vermilion Snapper are batch spawners with asynchronous oocyte development. Additionally, 17% of Vermilion Snapper in the actively spawning phase containing 24 hour POF's suggesting daily spawning is occurring. No immature fish of either sex were collected during this study (139 mm to 535 mm TL). Both histologicallydetermined phases and gonadosomatic index (GSI) patterns defined the spawning season ranged was from April to September. The spawning interval for Vermilion Snapper was estimated using the hydrated oocyte and post-ovulatory follicle methods, was 1.8 and 2.2 days respectively. Batch Fecundity (BF) estimates of 5,497 to 284,468 eggs/batch were determined using fish macroscopically classified as actively spawning (n = 22). Total fecundity (BF by spawning frequency) was estimated to range from 544,203 eggs/spawning season up to 28,162,332 eggs/spawning season. Mean relative batch iii fecundity was 70.7 eggs/g of gonad-free body weight. Estimates from this study can be directly incorporated into population assessments and provide a region-specific overview of life-history for the Vermilion Snapper from the north-central Gulf of Mexico. iv ACKNOWLEDGMENTS I would like to thank my thesis committee, Mark S. Peterson, Nancy J. Brown-Peterson and Robert T. Leaf, who guided me both academically and professionally throughout my tenure here at The University of Southern Mississippi. The majority of this research was funded by the National Fish and Wildlife Fund; however, various sources contributed funding in the form of scholarships as well. Specifically, I would like to thank the Division of Coastal Sciences for awarding me the Tom McIlwain Fisheries Endowment, the Gulf and Caribbean Fisheries Institute for the Ron Schmied Scholarship, and the MS-AFS student subunit for a student travel award. I am thankful for all of the above financial support I was awarded so that I could travel to scientific conferences, widen my sampling, and make contact with multiple stakeholders throughout the northern GOM. The Center for Fisheries Research and Development staff showed overwhelming support not only for me but for my project as well and helped me develop in my career as a fisheries biologist. I would like to thank Buck Buchanan for being my second reader for otoliths, as well as Alex Fogg and Robert Allman for showing me how to properly section and age Vermilion Snapper otoliths. I would like to also thank Capt. Lenny and Capt. Mike Thierry for allowing me not only to deckhand on their boats but to also meet them at the dock to collect samples. This research could not have happened without the cooperation and support of stakeholders in the recreational sector. My final thanks are to my graduate school companions, for all of their help, support, and comic relief throughout my time as a master's student. This research was conducted under the USM IACUC #16101302. v TABLE OF CONTENTS
Marine and Freshwater Behaviour and Physiology, 2016
This report describes a study of the gonad differentiation in fingerlings of European sea bass (Dicentrarchus labrax) belonging to different size groups. Fishes were divided into four groups according to their weight: Group 1 (4.5 ± 0.7 g), Group 2 (9.2 ± 0.8 g), Group 3 (14.8 ± 1.8 g), and Group 4 (21.8 ± 2.3 g). In all groups, low percentages of undifferentiated or early sexually differentiated fish were found. Higher percentages of fully differentiated ovaries were found in Groups 1 and 3. Fully differentiated testes occurred in 90% of Group 4. Ninety percent of fish in Group 2 had gonads with intratesticular oocytes. This highlights the occurrence of intersexual cases and suggests that at this size, the fish is susceptible to phenotypic plasticity. The results of the present study show that sexual differentiation of the gonads is found in fish at 4.5 g weight. The ambiguous relationship between the observed gonad morpho-functional characteristics and fish size suggests a subject-dependent sexual differentiation.
Growth, mortality, length-weight relationship, maturity and spawning of Lutjanus vitta were studied based on samples collected from 30 and 80 m depths along the southwest coast of India during October 1999-December 2009. The von Bertalanffy growth equation was derived as L t = 32.5 (1-e-0.66 (t-0.014)) during the year 2000; changes in these parameters during 2003-04 and 2007-08 are discussed in this paper. The lengthat-age was 12.3±1.36 cm, 18.9± 1.67 cm, 24.72± 1.58 cm, 28.9±0.98 cm and 31.5±0.94 cm in the I, II, III, IV and V year respectively. The annual natural, fishing and total mortality rates were 1.33, 0.85 and 2.18 respectively. The exploitation ratio (E) was 0.39, which indicates that this species is not under heavy fishing pressure. Recruitment was peak in March. Length-weight relationship was estimated for males and females, and later for the pooled data as W= 0.00000139 L 2.983. The relative condition factor (K n) does not vary significantly among the size groups but the seasonal condition factor (K s) is comparatively lower in the smaller size group. Higher gonado-somatic index (GSI) was seen during August-December. The length-at-first maturity was 15.8 cm for female and 14.5 cm for male. During October and November, the one-year age group (12.5cm () and 14 cm ()) appeared in the spawning grounds and extended the spawning activity by performing batch fecundity. The relative fecundity ranged between 2,22,016 ± 28,543 and 5,21,482 ± 67,044 eggs/fish.