Peces del Golfo de Nicoya, Pacífico, Costa Rica: actualización de las listas de los buques científicos Skimmer y Victor Hensen

Introducción: Desde mediados del siglo XX el estuario del Golfo de Nicoya (10o N & 85o W) ha sido la fuente principal de numerosos recursos pesqueros, como los moluscos, crustáceos y peces. El estuario está actualmente bajo impactos crecientes locales, regionales y globales. Las expediciones a bordo de los buques científicos Skimmer (1979-1980) y Víctor Hensen (1993-1994) aportaron datos multidisciplinarios en apoyo de políticas de manejo. Sin embargo, actualmente se necesita información actualizada. Objetivos: Actualizar las listas publicadas de peces recolectados en ambas expediciones y sugerir nuevas áreas de investigación para una futura evaluación del estado del ecosistema. Métodos: En el buque Skimmer las capturas de peces cubrieron un ámbito de profundidad de 10 a 50 m, con una red tipo otter. En el buque V. Hensen las capturas se hicieron entre 10 y 240 m de profundidad, con redes tipo otter y beam. En ambos cruceros se hizo a bordo la identificación de las especies y la medición de sus longitudes totales. Para actualizar las listas de especies se procedió a la verificación de los nombres vigentes con base en literatura reciente y la página World Register of Marine Species (WORMS). Agregamos a la lista los nombres de las especies identificadas en años recientes para el estuario y catalogados en la Colección Ictiológica del Museo de Zoología, Universidad de Costa Rica. Resultados: El total de especies identificadas es de 268 para ambos buques. Una especie de Syacium está pendiente de identificación. Del total, 19 especies corresponden a peces cartilaginosos y 249 a peces óseos. Los Scianeidae (corvinas) y los lenguados estuvieron representados por 31 y 32 especies, respectivamente. El género Symphurus (lenguados) fue el más diverso, con 11 especies. Dieciocho especies fueron identificadas después de la publicación de las listas originales. Ocho especies fueron descritas con base en ejemplares recolectados por ambos buques: Gymnothorax phalarus, Notarius biffi, N. cookei, Ophicthus mecoptera, O. melope, Sphoeroides rosenblatti, Trinectes xanthurus y Urotrygon cimar. Las especies presentes en más del 50 % de las 20 estaciones del Skimmer, fueron: Prionotus horrens (16), Sphoeroides trichocephalus (14), Syacium ovale (13) y Synodus scituliceps (13). En las 12 estaciones del V. Hensen, fueron: Porichthys margaritatus (9), S. scituliceps (8), Bollmannia chlamydes (6), Symphurus callopterus (6), S. elongatus (6) y Synodus evermanni (6). Los cinco peces de mayor longitud capturados por ambos buques, fueron: la raya látigo Hypanus longus (117 cm), el congrio Cynoponticus coniceps (103 cm), el bagre Sciades dowii (87 cm), la raya Narcine brancroftii (80 cm) y la corvina reina Cynoscion albus (75 cm). La longitud total máxima promedio de 137 especies medidas en el Skimmer fue de 26 cm y de 29 cm para las 164 medidas en el V. Hensen. Conclusiones: En vista del incremento del número de usuarios de los recursos estuarinos, es urgente una evaluación multidisciplinaria del ecosistema en apoyo a la propuesta de nuevas políticas de manejo. Los resultados facilitarían actualizar el Modelo Trófico del Golfo de Nicoya, una herramienta de manejo disponible desde 1998 y basada principalmente en datos obtenidos durante los cruceros del Skimmer y V. Hensen. Tensores del ecosistema, como la extracción de recursos, el ingreso de contaminantes y su posible relación con la disrupción endocrina, así como la presencia de barreras naturales como la hipoxia en la boca del estuario, deben ser incluidos en esa futura evaluación.

Introduction: Since the middle of the XXth century the Gulf of Nicoya estuary (10o N & 85o W) has been the main source of numerous fishing resources, such as mollusks, crustaceans, and fish. The estuary is presently under the increasing impact of local, regional and global stressors. The expeditions on board the R.V. Skimmer (1979-1980) and R.V. Hensen (1993-1994) research vessels provided multidisciplinary data on the estuary in support of management policies. However, updated information is still needed. Objectives: To update the published lists of fish species from both expeditions and make suggestions for new research areas for future evaluations of the ecosystem. Methods: The fish collections by the Skimmer covered a depth range of 10 to 50 m using an otter trawl net, and those aboard the Victor Hensen were made between 10 and 228 m depth using otter and beam trawl nets. The identification of the fish species and the measurement of its lenghts were made on board of both vessels. The species names were updated based on recent literature and the web page World Register of Marine Species (WORMS). The list of species identified in recent years based on voucher specimens from the estuary and deposited in the Ichthyology Collection of the Museum of Zoology, University of Costa Rica, was also included. Results: The total number of identified species from both vessels is 268. A species of Syacium is yet undescribed. Of the total, 19 are cartilaginous fishes and 249 are bony fishes. The Sciaenidae and the flatfishes were represented by 31 and 32 species, respectivley. The flatfish genus Symphurus was the most diverse, with 11 species. Eighteen species were identified after the publication of the original lists. Eight species were described based on specimens collected during the expeditions: Gymnothorax phalarus, Notarius biffi, N. cookei, Ophicthus mecoptera, O. melope, Sphoeroides rosenblatti, Trinectes xanthurus and Urotrygon cimar. The species present in more than 50% of the 20 Skimmer stations, were: Prionotus horrens (16 stations), Sphoeroides trichocephalus (14), Syacium ovale (13) and Synodus scituliceps (13). In the 12 stations of the V. Hensen there were: Porichthys margaritatus (9), S. scituliceps (8), Bollmannia chlamydes (6), Symphurus callopterus (6), S. elongatus (6), and Synodus evermanni (6). The five longer specimens collected by both vessels, were: the longtail sting ray Hypanus longus (117 cm), the pike conger Cynoponticus coniceps (103 cm), the brown sea catfish Sciades dowii (87 cm), the electric ray Narcine brancroftii (80 cm), and the queen corvina Cynoscion albus (75 cm). The average total length for 137 species measured during the Skimmer cruises was 26 cm, and 29 cm for the 164 measured during the V. Hensen survey. Conclusions: In view of the increasing number of users of the estuarine resources, it is urgent a multidisciplinary evaluation of the ecosystem in support of new management policies. The expected results may facilitate updating the Gulf of Nicoya Trophic Model, a management tool available for the estuary since 1998 and based mainly on information gathered during both expeditions. Ecosystem stressors, such as the extraction of resources, the input of pollutants and its possible link to endocrine disruption, as well as the presence of natural barriers such as hypoxia at deeper waters at the mouth of the estuary must be taken into account in a future evaluation.

Total mercury in the fish Trichiurus lepturus from a tropical estuary in relation to length, weight, and season

O estuário do rio Goiana (7º30’S 34º47’W) é um típico estuário de região tropical semi-árida. Esse estuário abriga uma fauna rica de peixes, crustáceos e moluscos que tem um importante papel na vida da população tradicional. Ele também é o principal receptor de efluentes da agroindústria da cana-de-açúcar e esgoto das comunidades e vilas. Trichiurus lepturus (n = 104), do estuário do rio Goiana foram examinados para o conteúdo de mercúrio total durante dez meses (2005 a 2007) ao longo de duas estações secas e parte de uma estação chuvosa. Os indivíduos estudados apresentaram peso (P) (204,1±97,9 g) e comprimento total (CT) (63,1±10,1 cm, variação 29,5-89,0 cm) com uma correlação significativa (p<0,05). As correlações entre CT e Hg-T (r = 0,37286) e entre P e Hg-T (r = 0,38212) foram positivas e significativas. A ANOVA (2 fatores) (n = 81) mostrou que o CT e P apresentaram diferenças significativas (p<0,05) entre as estações. O Hg-T apresentou diferença em relação ao fator estação (p<0,05). A correlação entre Hg-T e a chuva apresentou uma relação negativa e significativa (r = -0,56; p<0,05). A precipitação pluviométrica influenciou fortemente a bioacumulação de mercúrio nessa espécie. Os meses secos apresentaram relativamente concentrações de mercúrio maiores do que o final da estação chuvosa. Isso sugere que a menor precipitação pluviométrica, e consequentemente a menor quantidade de material particulado e menor produtividade primária no estuário, torna o mercúrio mais biodisponível. Peixes desse estuário podem ser consumidos pela população humana ao longo de todo ano.

The Goiana River Estuary (7º30’S 34º47’W) is a typical estuary of the semi-arid tropical regions. This estuary shelters a rich fauna of fish, crustaceans and mollusks which play an important role in the life of traditional populations. It is also the main recipient of the effluents from the sugarcane agro-industry and sewage from settlements and villages. Trichiurus lepturus (n = 104), from the Goiana Estuary were examined for total mercury contents during ten months (2005 to 2007) spaning two dry seasons and part of a rainy season. The studied individuals showed weight (W) (204.1±97.9 g) and total length (TL) (63.1±10.1 cm, range 29.5-89.0 cm) with a significant (p<0.05) correlation. Correlation between TL and Hg-T (r = 0.37286) and between W and Hg-T (r = 0.38212) were positive and significant (p<0.05). Two-way ANOVA (n = 81) showed that TL and W had significant difference (p<0.05) among seasons. The Hg-T showed differences in relation to the factor season (p<0.05). The correlation between Hg-T and rainfall showed a negative and significant relation (r = -0.56; p<0.05). Rainfall strongly influenced the bioacumulation of mercury in this species. Dryer months showed relatively higher mercury concentrations than the end of the rainy season. Less rainfall, and consequently less particulate matter and less primary production in the estuary, make mercury more bioavailable. Fish from this estuary are fit for human consumption at all times of the year.

Spatial choice is biased by chemical cues from conspecifics in the speckeled worm eel Myrophis punctatus

The speckeld worm eel Myrophis punctatus lives in high-densities assemblages, and usually digs through, or lies on the substrate. These behaviours could lead to chemical marks on the substrate and could modulate the spatial distribution in this species. We tested the hypothesis that the spatial choice of the speckled worm eel is modulated by the presence of conspecific odour on the substrate. Here, we showed that the speckled worm eel avoids the substrate area containing the conspecific odour, indicating that this chemical cue modulates the eel's spatial decision. The eels clearly detected the conspecific's odour. This perception might indicate the presence of conspecifics into the substrate. Since the eels avoided an area containing conspecific odour, we suggest this may be a response that avoids the consequences of invading a resident-animal's territory.

A enguia mirongo-mirim Myrophis punctatus vive em agrupamentos de alta densidade populacional e comumente se enterra ou permanece sob o substrato. Esses comportamentos podem levar a marcas químicas no subtrato e podem, portanto, modular o uso do espaço nessa espécie. Neste estudo, testamos a hipótese de que a preferência espacial da enguia mirongo-mirim é influenciada pela presença de odor do animal coespecífico no subtrato. Mostramos que as enguias evitam a área que contém tal odor, indicando que as decisões de ocupação espacial podem ser influenciadas por pistas químicas de coespecíficos. As enguias claramente detectaram o odor de um animal coespecífico e essa percepção poderia ser um indicativo da presença de um coespecífico enterrado no substrato. Visto que elas evitam uma área contendo tal odor, sugerimos que isso poderia ser uma resposta para evitar invadir o território de um animal residente.

Hábitos alimenticios y ecología trófica del pez Lutjanus griseus (Pisces: Lutjanidae) asociado a la vegetación sumergida en la Laguna de Términos, Campeche, México

Feeding habits and trophic ecology of the fish Lutjanus griseus (Pisces: Lutjanidae) associated with submerged vegetation in Laguna de Términos, Campeche, Mexico. In Campeche, Mexico, the Laguna de Términos has Thalassia testudinum beds inhabited by the grey snapper, Lutjanus griseus (Linnaeus 1758). Along one year, we collected 994 individuals and 672 had food in their stomachs; we recorded number, weight, and frequency of trophic groups, and the index of relative importance. Dominant food components were Farfantepenaeus duorarum and Palemonetes octaviae, Eucinostomus gula (Cuvier 1830) and Libinia dubia. Salinity and temperature were related to the number of individuals collected and with greater fish consumption by large L. griseus. The trophic niche breadth index was calculated for six size-classes of fish. The smallest and the largest fish had the lowest index values, whereas medium-size snappers had higher values. This snapper has a preference for habitats with submerged vegetation. The percentage of fish with food in their stomachs was higher during dark hours, providing evidence of the nocturnal habits of this fish. Rev. Biol. Trop. 55 (3-4): 989-1004. Epub 2007 December, 28.

Se presentan los resultados de un estudio de los hábitos alimenticios de Lutjanus griseus asociado a la vegetación sumergida en El Cayo, Laguna de Términos, Campeche, México. La investigación se realizó siguiendo un diseño de muestreo intensivo tanto en escala espacial como temporal. Se recolectaron un total de 994 individuos, de los cuales 672 tenía alimento en sus estómagos. Se analizaron los porcentajes en número, peso y frecuencia de los grupos tróficos, así como el índice de importancia relativa. Los componentes alimenticios dominantes fueron Farfantepenaeus duorarum, Palaemonetes octavie, Eucinostomus gula y Libinia dubia. La salinidad y la temperatura se relacionaron con el número de individuos colectados así como con un incremento en el consumo de peces por los individuos de mayor talla. Se calculó el índice de diversidad de dieta para seis clases de talla de los peces, examinándose su variación a través del año. Los peces de menor y mayor talla mostraron los valores más bajos de este índice, mientras que los organismos de las tallas intermedias presentaron los valores más altos. Los resultados mostraron que L. griseus tiene preferencia por hábitats con vegetación sumergida. El porcentaje de peces con alimento en sus estómagos fue mayor durante la noche que durante el día, evidenciando los hábitos nocturnos de esta especie.