Seasonal foods, gonadal maturation, and length-weight relationships for nine fishes commonly captured by shrimp trawl on the Northwest Gulf of Mexico Continental Shelf

Recent emphasis on ecosystem approaches to fisheries management renews interest in, and the need for, trophic information about fish communities. A program was started in 1980 at the National Marine Fisheries Service Galveston Laboratory to develop a trophic database for continental shelf fishes. Collections were made during 1982-1983 that were processed but never published, yet the data remain valid today for historical purposes and for delimiting food web components within ecosystem assessments. I examined spring, summer, and fall foods in offshore populations of nine common species of trawl-susceptible fishes, with particular reference to predation on commercial penaeid shrimps (Farfantepenaeus and Litopenaeus). Diets were evaluated with the Index of Relative Importance (IRI) which combines the occurrence, number, and weight of each food item. Bank sea bass (Centropristis ocyurus) and bighead searobin (Prionotus tribulus) primarily consumed crabs, more so by larger than smaller fish. Inshore lizardfish (Synodus foetens) was almost entirely piscivorous. Ocellated flounder (Ancylopsetta ommata) consumed fishes, crabs, and stomatopods. Dwarf sand perch (Diplectrum bivittatum), blackwing searobin (Prionotus rubio), rock sea bass (Centropristis philadelphica), southern kingfish (Menticirrhus americanus), and red snapper (Lutjanus campechanus) fed mainly on shrimps. Most fish diets varied with respect to size (age), time of day, area sampled, depth, or season. Rimapenaeus and Sicyonia were the most frequently identified shrimp genera - only five Farfantepenaeus and no Litopenaeus were identified in almost 4,300 fish stomachs. I also examined gonadal development and documented fish length-weight relationships. Ripe gonads were most frequently found during summer in dwarf sand perch, during fall in ocellated flounder and bighead searobin, and during spring for other species, except no ripe red snapper or bank sea bass were collected. Rock sea bass was found to be a protogynous hermaphrodite, while dwarf sand perch is a synchronous hermaphrodite. Only ocellated flounder and southern kingfish exhibited sex-related differences in length-weight relationships. (PDF contains 40 pages.)

First gonadal maturation of Pinirampus pirinampu (Siluriformes: Pimelodidae) in the Pantanal, Mato Grosso do Sul State, Brazil

Informações sobre o ciclo reprodutivo de espécies exploradas pela pesca são imprescindíveis para o seu manejo adequado. O tamanho de início da atividade reprodutiva do Pinirampus pirinampu (Spix, 1829) foi determinado. Os exemplares foram capturados em setembro, outubro e dezembro de 1997 e fevereiro e março de 1998. O estádio de desenvolvimento gonadal foi identificado macroscopicamente. O índice gonadossomático médio (IGS), calculado mensalmente, foi utilizado como indicador da época de desova. Para determinação do comprimento da primeira maturação gonadal agruparam-se, separadamente, machos e fêmeas por classes de comprimento em imaturos e adultos. Os resultados referentes aos indivíduos adultos foram lançados em gráficos e a mediana correspondeu à estimativa do comprimento no qual 50% dos indivíduos atingem a maturidade (L50). Foi também determinado o L100, estimativa do comprimento em que todos os indivíduos estão aptos à reprodução. Machos e fêmeas em processo de maturação gonadal foram encontrados a partir de outubro, com maior freqüência em fevereiro, e, somente a partir deste mês, foram encontrados indivíduos com gônadas esvaziadas. O índice gonadossomático mostrou que a partir de setembro inicia-se o processo de desenvolvimento gonadal, com seu valor máximo em fevereiro. O L50 para fêmeas foi 574 mm e para machos foi 536 mm. O L100 para fêmeas foi 590 mm e para os machos, 580 mm.

Gonadal Maturation in the Cobia Rachycentron canadum from the Northcentral Gulf of Mexico

Gonadal maturation of cobia, Rachycentron canadum, was evaluated by examining 508 specimens from its recreational fishery. Specimens were collected off southeast Louisiana to northwest Florida by hook-and-line during February through October 1987-1991. Fork lengths (FL) of these fish ranged from 580-1,530 mm, with corresponding weights of 2.0-43.5 kg. The female:male ratio was 1:0.37. Using a combination of oocyte size frequency and histological assessment of many of the fish, we determined that females were ripe from May through September, with atretic oocytes occurring in some fish from July through October. Degenerating hydrated oocytes in July and October and the presence of resting ovaries in July suggest two major spawning periods; however, monthly gonosomatic indices peaking in May, followed by a steady decline, do not support that finding. Ovaries were placed into undeveloped, early developing, mid-developing, or late developing categories based upon oocyte size-frequency distributions. Developing ovaries had two or three modes of oocytes larger than 30 μm. Batch fecundity was estimated to be 2.6×106 - 1.91×108 oocytes, depending on the size of fish/ovaries. The smallest female with oocytes exhibiting vitellogenesis was 834 mm FL. This fish was 2 years old based its otolith evaluation. The smallest male with an abundance of spermatozoa in its testes was 640 mm FL and 1 year old based on otolith evaluation; smaller males were not examined. Females larger than 840 mm FL had vitellogenic oocytes in March and April. A few fish still had vitellogenic oocytes in early October, but none did by late October. When Gilson’s fluid was used to assess ovarian tissue, the fresh weight of the tissue was reduced by 20% after being stored for 3 months. The diameter of oocytes shrunk about 25% in Gilson’s fluid which was 11% less than those fixed in formalin, embedded in paraffin, and sectioned. Tissue sections from specific individuals, each demonstrating a variety of different developmental stages, were similar regardless of whether they were obtained from the anterior, middle, or posterior portion of either ovary.

Seawater acidification affects the physiological energetics and spawning capacity of the Manila clam Ruditapes philippinarum during gonadal maturation

Ocean acidification is predicted to have widespread implications for marine bivalve mollusks. While our understanding of its impact on their physiological and behavioral responses is increasing, little is known about their reproductive responses under future scenarios of anthropogenic climate change. In this study, we examined the physiological energetics of the Manila clam Ruditapes philippinarum exposed to CO2-induced seawater acidification during gonadal maturation. Three recirculating systems filled with 600 L of seawater were manipulated to three pH levels (8.0, 7.7, and 7.4) corresponding to control and projected pH levels for 2100 and 2300. In each system, temperature was gradually increased ca. 0.3 °C per day from 10 to 20 °C for 30 days and maintained at 20 °C for the following 40 days. Irrespective of seawater pH levels, clearance rate (CR), respiration rate (RR), ammonia excretion rate (ER), and scope for growth (SFG) increased after a 30-day stepwise warming protocol. When seawater pH was reduced, CR, ratio of oxygen to nitrogen, and SFG significantly decreased concurrently, whereas ammonia ER increased. RR was virtually unaffected under acidified conditions. Neither temperature nor acidification showed a significant effect on food absorption efficiency. Our findings indicate that energy is allocated away from reproduction under reduced seawater pH, potentially resulting in an impaired or suppressed reproductive function. This interpretation is based on the fact that spawning was induced in only 56% of the clams grown at pH 7.4. Seawater acidification can therefore potentially impair the physiological energetics and spawning capacity of R. philippinarum.

Seguimiento en cautiverio de la maduración gonadal y desove del lenguado Paralichthys adspersus (Steindachner)

Se describe el método de observaciones in vivo de la madurez gonadal de Paralichthys adspersus. Las observaciones microscópicas de las gónadas se realizaron con muestras provenientes de las canulaciones intra-ováricas e intra-testiculares, se analizó y describió el desarrollo ovocitario y espermatogénico en individuos mantenidos en condiciones de laboratorio para determinar el estado de madurez gonadal y el momento adecuado para la inducción hormonal. Se interpreta el significado de la atresia ovocitaria en las gónadas de lenguado.

Escala de madurez gonadal de hembras de lenguado de ojo grande Hippoglossina macrops (Steindachner, 1876)

El lenguado de ojo grande Hippoglossina macrops es un recurso potencial poco estudiado. Tiene una amplia distribución latitudinal (3°S-8°S) y batimétrica (90-380 m de profundidad). Para determinar la escala de madurez gonadal, se analizaron 570 ovarios colectados en los Cruceros de Evaluación de Recursos Demersales de los años 2003 al 2007. Se determinó seis estadios de madurez gonadal: 0 (virginal), I (reposo), II (en maduración), III (maduro), IV (desovante), V (recuperación), los que permiten conocer con mayor certeza, la condición reproductiva de las hembras de esta especie y su principal periodo de reproducción.

Crescimento, desenvolvimento gonadal e composição muscular de matrinxãs (Brycon cephalus) submetidos à restrição alimentar e realimentação durante um ano

Neste trabalho, avaliou-se o efeito da restrição de ração alternada com realimentação no crescimento, desenvolvimento gonadal e composição muscular de matrinxãs (Brycon cephalus) adultos, de ambos os sexos, durante um ano (janeiro de 1998 a janeiro de 1999). Foram utilizados 135 peixes, separados em dois grupos: controle, alimentado diariamente até aparente saciação, e experimental, submetido ininterruptamente a ciclos de três dias de alimentação/2 dias de restrição de ração (40% de restrição ao mês). Foram realizadas 7 amostragens, nas quais foram utilizados 8 a 10 peixes por grupo. Após anestesia, os peixes foram pesados e as gônadas foram retiradas para determinação do IGS, sexo e fase do ciclo reprodutivo. Porções dos músculos branco e vermelho foram retiradas para determinação da porcentagem de lipídio total, proteína bruta, matéria seca e umidade. Os resultados mostraram que a estratégia alimentar utilizada não afetou o crescimento, o desenvolvimento gonadal e a composição muscular do matrinxã. A restrição de ração seguida por realimentação parece ter desencadeado mecanismos de ajuste metabólico para melhor utilização do alimento e aporte suficiente de energia para o crescimento, processo de maturação gonadal e composição corporal. É possível estabelecer formas de manejo alimentar mais econômicas para o matrinxã sem que processos fisiológicos importantes sejam afetados.

Escala y talla de primera madurez gonadal en “NAVAJA” Tagelus dombeii (Lamarck, 1818), entre las zonas Parachique - Las Delicias, 2009

Para el estudio de la gametogénesis, escala de madurez y estimación de la talla de primera madurez gonadal de “navaja” Tagelus dombeii, las muestras procedieron de las zonas Caleta de Parachique y Las Delicias, y fueron colectadas a bordo de embarcaciones marisqueras por buzos artesanales, durante Enero – Diciembre del año 2009. La zona para tomar las muestras comprendieron desde los grados 05º 40' 33.3'' (LS) hasta 05º 49' 21.8'' (LS). En el estudio de la gametogénesis, se observó que los ovarios presentaron tres tipos de ovocitos: ovocito inmaduro (OI), ovocito en maduración (OEM) y ovocito maduro (OM), además del ovocito atrésico (OA) para las hembras, mientras que para los machos las células sexuales encontradas fueron: espermatogonio = SG, espermatocito = SC y espermatozoide = SP. La escala microscópica de madurez gonadal para “navaja” T. dombeii fue establecida con seis estadios, siendo estos: Virginal = 0, Reposo = I, En Maduración = II, Maduro =III, Desovante/Expulsante = IV y Recuperación = V. Así mismo, se estableció, que la talla de primera madurez gonadal es de 61 mm de longitud total (LT) para las hembras y 58 mm para machos, obteniendo un promedio de 58 mm LT. Mientras que la talla de primer desove/expulsión fue de: 67 mm (LT) para hembras y 66 mm LT para machos siendo promedio para ambos sexos de 66 mm LT. Además, se reporta la capacidad de T. dombeii de cambiar el sexo de hembra a macho (hermafroditismo protógino).

Circannual rhythms of maturation in the female rainbow trout and their entrainment by changes in photoperiod

The importance of endogenous rhythms in the photoperiodic control of the annual reproduction cycle in female rainbow trout was investigated. The effect of photoperiod regimes on the different stages of maturation was assessed by recording the timing of ovulation and from quantifying associated changes in serum oestradiol-17,testosterone and total calcium. Maintained under constant 6L:18D and constant temperature for up to four years, rainbow trout exhibited an endogenous rhythm of maturation with a periodicity of approximately one year. This rhythm of maturation appears to be driven by an autonomous circannual oscillator or clock which can be dissociated from the neuroendocrine mechanisms controlling gonadal maturation. Under conditions of constant 18L:6D or LL the periodicity of the maturation rhythm was 5.5-6 months; it is suggested that this periodicity may be caused by a splitting or uncoupling of at least two circannual clocks involved in the control of maturation. Abrupt changes in the length of the photoperiod act as a zeitgeber to entrain the endogenous rhythm of maturation. Whether the timing of maturation is advanced or delayed depends primarily on the direction of the change in photoperiod and its timing in relation to the phase of the rhythm, with the magnitude of the alteration in photoperiod having only a supplementary effect. The effect of specific changes in photoperiod on the entrainment of the maturation cycle can be described in terms of a phase-response curve. Photic information is transduced, probably by the pineal gland, into a daily rhythm of melatonin; exposure of rainbow trout to skeleton and resonance photoperiod regimes indicated that daylength measurement is effected by endogenous circadian clock(s) rather than by hour-glass mechanisms. A gating mechanism is closely associated with the circannual clock which determines the timing of onset of maturation in virgin female rainbow trout, only allowing fish that have attained a threshold stage of development to undergo gonadal maturation. Collectively the results support the hypothesis that the female rainbow trout exhibits an endogenous circannual rhythm of maturation which can be entrained by changes in photoperiod.

Crescimento, desenvolvimento gonadal e composição muscular de matrinxãs (Brycon cephalus) submetidos à restrição alimentar e realimentação durante um ano

Neste trabalho, avaliou-se o efeito da restrição de ração alternada com realimentação no crescimento, desenvolvimento gonadal e composição muscular de matrinxãs (Brycon cephalus) adultos, de ambos os sexos, durante um ano (janeiro de 1998 a janeiro de 1999). Foram utilizados 135 peixes, separados em dois grupos: controle, alimentado diariamente até aparente saciação, e experimental, submetido ininterruptamente a ciclos de três dias de alimentação/2 dias de restrição de ração (40% de restrição ao mês). Foram realizadas 7 amostragens, nas quais foram utilizados 8 a 10 peixes por grupo. Após anestesia, os peixes foram pesados e as gônadas foram retiradas para determinação do IGS, sexo e fase do ciclo reprodutivo. Porções dos músculos branco e vermelho foram retiradas para determinação da porcentagem de lipídio total, proteína bruta, matéria seca e umidade. Os resultados mostraram que a estratégia alimentar utilizada não afetou o crescimento, o desenvolvimento gonadal e a composição muscular do matrinxã. A restrição de ração seguida por realimentação parece ter desencadeado mecanismos de ajuste metabólico para melhor utilização do alimento e aporte suficiente de energia para o crescimento, processo de maturação gonadal e composição corporal. É possível estabelecer formas de manejo alimentar mais econômicas para o matrinxã sem que processos fisiológicos importantes sejam afetados.

Length-weight relationships and relative conditions of two sciaenids Otolithes cuvieri Trewavas and Johnius elongatus Mohan from the Karachi coast

Estimates of length-weight relationship in Otolithes cuvieri justify separate equations for males (log W =-5.0100+3.1365 log L) and females (log W =-5.2000+3.1006 log L). Relative condition factor "Kn" was found to be 0.877-1.946 in males and 0.879-1.328 in females. High "Kn" values during March to September at 180-220 mm TL in either sexes are indicative of the maturation of gonads. Separate equations for length-weight relationship are also justified for males (log W = -5.1126 + 3.0690 log L) and females (log W = -5.6400 + 3.3070 log L) of Johnius elongatus . "Kn" values were found to be 0.924-1.894 for males and 0.894-1.087 for females. High "Kn" values during January-May and August-September at 130 mm TL onward are indicative of gonadal maturation.

A simple method of tagging prawns

The recognition of individual animals is crucial to many aspects of research. Prawns (Penaeus monodon) present unique difficulties in this respect since they molt regularly. Thus, almost all tagging and marking methods developed for prawns so far have proven inadequate. Some tags or marks are lost during molting; others cause injury to the prawns. A new and efficient method has been developed at the Igang Seafarming Station of the Aquaculture Department. Rectangular brass tags measuring 5 mm by 20 mm and numbered consecutively are used. The prawn is held gently but firmly at the base of the carapace with the left hand while the right hand slips the brass tag around the stalk of the unablated eye and presses the tag gently. All tagging must be made under water to avoid stress. From May 29 to September 7 1977 to a total of 348 unilaterally-ablated adult female prawns were tagged on the unablated eyestalk in 5 batches to enable individual observations on gonadal maturation, molting, and growth. Periodic examinations were made four times a month to coincide with the different phases of the lunar cycle. On each examination, survival and recovery rates were recorded. The data included death due to immediate mortality during ablation and loss to cannibalism for the duration of the experiments. In all five tagging experiments, most of the prawns recovered had their tags intact. These included even dead and molting animals. The eyestalk tagging method is suitable for prawns because the tags can be attached without causing injury and has no effect on the rate of growth, maturity, molting and behavior of the animal. The tags are identifiable and permanent; they remain attached to the animal even after death.

Histoarchitecture, seasonal variation and reproductive function of the neuroendocrine organ, brain of freshwater prawn, Macrobrachium gangeticum

Histoarchitecture, seasonal variation and reproductive function of the neuroendocrine structure, brain of freshwater prawn Macrobrachium gangeticum were studied. Three types of NSCs - 'B', 'C' and 'D' were found to be concentrated in four groups in brain. These cells showed larger diameters and higher activity during breeding season. In case of females, the 'C' cells were more active during vitellogenic period. Brain extracts were found to induce gonadal maturation of both males and females.

Study on the reproductive biology of Pinctada fucata (Gould) (Mollusca: Pteriidae)

Annual cycle of gonad development and spawning in pearl oyster, Pinctada ficata (Gould) in Nakhiloo, Northeast Persian Gulf, was investigated over two years from August 1994 to June 1996. Gonadal condition was assessed by staging criteria to describe gametogenic development from histological preparations of randomly collected individuals of all sizes. A bimodal gametogenic pattern with summer and autumn spawning periods was evident throughout the study. Gametogensis commenced in November-December which proceeded by major gonadal maturation during February-April. Summer spawning was observed from April to July with major spawning at the latter end. During spawning peak in July, low level of gametogensis was noticed. Gametogenic activity was picked up again in August-September which proceeded by autumn spawning from September to December. Towards the end of spawning season, incidence of gonadal inactivation increased. Minimum level of gonadal activity was observed in November. Temperature regime appears to have influential role in regulation of gametogenic and spawning processes. Gonadal development and spawning trends were similar in both sexes. P. radiaata was found to be protandrous hermaphrodite which matured as a male at shell height greater than 20 mm. Biseivality was uncommon and the sex ratio was about 1:1. Ultrastructure of gametes were investigated in the Pictada fucata (Gould). "Auxiliary cells" closely accociated with developing oocytes were observed. Each oocyte seems to be associated with only one secretory cell. which is characterized by an abundant rough endoplasmic reticulum at the onset of vitellogenesis. Contact between this cell and a developing oocytes is maintained by a desmosome-like junction which can be observed when the vitelline coat is formed. these "auxiliary or nursing cells" seem to play a tropic role in vitellogenesis, and may be involved in the formation of the vitelline coat of the oocytes. Oocytic degeneration is observed in this species, it is a continuous phenomenon of varing intensity throughout the year. The ultrastructural changes resulting in lysis of the oocyte are described. Mature spermatozoa consist of a broad, cap-shaped acrosomal vesicle, subacrosomal material, a round nucleus, two triplet substructure centrioles surrounded by four spherical mitochondria, and a flagellum anchored to the distal centriole and plasma membrane. Spermatozoa of Plucata closley resemble to those of other investigated Pteriidae. Changes in proximate composition of soft tissue and gonadal cycle of Pinctada fucata was studied. Mobilization and utilization of stored reserves are apparent during gametogenesis and gonadal maturation. Protein reserves are utilized during spermatogenesis while reserved carbohydrates form the main energy donor in oogenesis. The role of lipid as am.: energy reserve is second to that of carbohydrate.