ABSTRACT
The age and growth of fish populations is a critical issue for stock assessment, population dynamics and fishery management. Spawner biomass, mortality, growth, recruitment and age at maturity can be misconstrued if the age estimator is inaccurate. Age can be estimated by annuli count, but this requires expertise and is expensive. Otolith weight (OW) is a good indicator of how long a fish has lived, because OW increases during an individual's life. Seriola lalandi is a migratory fish and is an important resource for local fishermen in northern Chile. Aspects of its biology, i.e., age and growth, remain unknown, at least for the population annually arriving in northern Chile. Fish of a known age (n = 105; from 5.5 to 25.7 cm in FL) from yellowtail aquaculture facilities at Universidad de Antofagasta allowed us to estimate the growth rate of OW, and fish obtained from local fishermen (n = 71; from 37.9 to 109 cm in FL) allowed us to estimate the age and growth of S. lalandi from the analysis of OW, without the need for calibration. The following four models were fitted with the known ages and fork lengths: the von Bertalanffy growth function, the Gompertz and logistic models and the seasonalized von Bertalanffy growth function. The latter model showed the best adjustment (according to the Akaike information criterion) with the following parameters: L∞, 98.58 cm.; K, 0.59; t0, 0.07; ts, 0.84; and C, 0.97.
ABSTRACT
Coastal marine upwelling famously supports elevated levels of pelagic biological production, but can also subsidize production in inshore habitats via pelagic-benthic coupling. Consumers inhabiting macroalgae-dominated rocky reef habitats are often considered to be members of a food web fuelled by energy derived from benthic primary production; conversely, they may also be subsidized by materials transported from pelagic habitats. Here, we used stable isotopes (δ13 C, δ15 N) to examine the relative contribution of pelagic and benthic materials to an ecologically and economically important benthivorous fish assemblage inhabiting subtidal macroalgae-dominated reefs along ~1,000 km of the northern Chilean coast where coastal upwelling is active. Fish were isotopically most similar to the pelagic pathway and Bayesian mixing models indicated that production of benthivorous fish was dominated (median 98%, range 69-99%) by pelagic-derived C and N. Although the mechanism by which these materials enter the benthic food web remains unknown, our results clearly highlight the importance of pelagic-benthic coupling in the region. The scale of this subsidy has substantial implications for our basic understanding of ecosystem functioning and the management of nearshore habitats in northern Chile and other upwelling zones worldwide.
Subject(s)
Ecosystem , Fishes/physiology , Seaweed , Animals , Bayes Theorem , Chile , Food ChainABSTRACT
Las óptimas condiciones de cultivo en el manejo de reproductores de Psetta maxima permiten obtener una mejor cantidad y calidad de huevos así como larvas viables con una mayor producción. Para evaluar las óptimas condiciones se utilizaron ejemplares mantenidos en condiciones de cultivo acondicionados desde los 3 hasta los 24 meses de vida, para así llegar a conformar un stock de reproductores. Al final de la experiencia, los huevos en los estanques experimentales se presentaron circulares y transparentes, al igual que las larvas recién eclosionadas que se hallaban rectas y muy bien pigmentadas, signos de buena calidad de huevos y larvas. Los cambios en la relación macho-hembra y densidad, fueron las variables a evaluar, llegando a obtener resultados satisfactorios por periodo productivo de las hembras y una mejor calidad y cantidad de huevos y larvas viables, en un periodo de cuatro años. Las mortalidades de reproductores en el periodo desove y post-desove bajaron significativamente. Estadísticamente no existe una diferencia significativa entre los estanques experimentales y controles. Desde el tercer año, la producción de huevos y larvas en los estanques experimentales mostró un incremento cercano al 90 por ciento en huevos y a un 60 por ciento en larvas. En los dos últimos años el porcentaje de larvas cosechadas en estos estanques, mostró un incremento del 7 por ciento al 12 por ciento en larvas sembradas y una disminución del 9 por ciento al 13 por ciento en larvas eliminadas, principalmente en el estanque 4.
The optimal culture conditions in broodstock management of Psetta maxima allow obtaining better quantity and quality of eggs and viable larvae, increasing the production. In order to evaluate the optimal conditions the specimens kept under culture conditions were used, in a period of 3-24 months of life, thus forming a broodstock stock. At the end of the experiment, the eggs in the experimental tanks resulted circular and transparent, as well as newly hatched larvae that were straight and well pigmented, signs of a good quality of eggs and larvae. Changes in the male-female and density ratio were the assessed variables, reaching satisfactory results per productive period of females and better quality and quantity of eggs and viable larvae during the period of four years. The mortality rate of broodstock in spawning and post-spawning period decreased significantly. Statistically there were no significant difference between experimental and control tanks. From the third year, egg and larvae production in experimental tanks showed an increase of about 90 percent for eggs, and 60 percent for larvae. In the last two years the percentage of harvested larvae in these tanks showed an increase of 7 percent to 12 percent for sown larvae and a decrease of 9 percent to 13 percent for eliminated larvae, mostly in tank 4.
Subject(s)
Animals , Eggs , Flatfishes , Larva , Aquaculture , FisheriesABSTRACT
La tasa de mortalidad en las etapas embrionarias y larvales de los peces marinos se asocia al éxito de un cultivo y es necesario optimizar los procedimientos de este a nivel de desarrollo embrionario y primeros estadios larvales para una óptima supervivencia larval y una mejor producción de juveniles. Para evaluar el efecto de la temperatura en la supervivencia embrionaria y larvaria del turbot, los huevos fecundados de dos reproductores se trasladaron a estanques cónicos de incubación a tres diferentes temperaturas (12,5; 15,5 y 18,5C). Los huevos que se encontraban a temperaturas extremas (12,5 y 18,5C) tuvieron un menor desarrollo embriológico, con un porcentaje de mortalidad diaria significativamente mayor en los tres primeros días y al término de la incubación, especialmente durante la eclosión de los huevos (supervivencia del 10%), y sin variaciones al término del experimento, cuando las larvas tenían seis días de vida. La duración del desarrollo embrionario hasta la eclosión del huevo también estuvo determinada por la temperatura de incubación, con un mayor número de huevos eclosionados y cosechados a la temperatura de 15,5°C (supervivencia de un 20%). Las diferencias significativas en el desarrollo embriológico del turbot a tres diferentes temperaturas de incubación demuestran la importancia de este parámetro en la viabilidad del desarrollo embrionario y los primeros estadios larvales de P. maxima.
The mortality rate in embryonic and larval stages of marine fish is associated with the success of a culture, being necessary to optimize the procedures from this to the level of embryonic development and early larval stages for an optimal larval survival and better juvenile production. In order to evaluate temperature effect on embryonic and larval survival of Turbot, fertilized eggs of two reproductives were transferred to the conical incubation tanks at three different temperatures (12.5; 15.5 and 18.5C). The eggs that were at extreme temperatures (12.5 y 18.5C) had a minor embryonic development, with a daily mortality rate significantly higher in the first three days and at the end of incubation, especially during the egg eclosion (10% survival), and without variations at the end of the experiment, when larvae had six days of life. The duration of embryonic development up to the egg eclosion was also determined by incubation temperature, with a higher number of hatched eggs and harvested at the temperature of 15.5°C (20% survival). Significant differences in the embryonic development of Turbot at three different incubation temperatures indicate the importance of this parameter on the viability of embryonic development and early larval stages of P. maxima.
Subject(s)
Animals , Temperature , Flatfishes/growth & development , Larva/growth & developmentABSTRACT
Se determina la influencia del aumento de la temperatura (17 a 20°C), la ración (2,5 por ciento a 3,5 por ciento del peso día) y la frecuencia de alimentación (4 a 6 veces día), en el crecimiento y la supervivencia de juveniles de turbot (Psetta maxima) en un sistema productivo comercial durante 35 días. Los resultados muestran que el crecimiento de los juveniles provenientes del nuevo protocolo de cultivo experimental ensayado es mayor y muestra una tasa específica de crecimiento, significativamente diferente respecto a los cultivados con el protocolo base, sin afectar la supervivencia, la que se mantiene en 99,8 por ciento. Se sugiere realizar mayores estudios para aislar o definir exactamente el efecto sinérgico de las variables definidas, así como complementar los resultados obtenidos con un estudio econométrico que evalúe su real aporte económico dentro de la cadena productiva del cultivo...
The influence of water temperature (17 and 20°C), frequency (4 and 6) and feed ration level (2.5 percent and 3.5 percent) on the growth and survival of juvenile turbot (Psetta maxima) in a commercial productive system was investigated over 35 days. The results indicate that fish from the experimental protocol exhibited better growth and significant difference in specific growth rate than those raised with basic protocol, without affecting survival that remains at 99.8 percent. It is suggested further studies to isolate or define exactly the synergistic effect of the variables defined and complement the results obtained with an econometric study which evaluate their real economic contribution within the productive chain of culture...