Beschreibung: We employed 3-D biophysical modeling and dispersion kernel analysis to explore inter-annual and inter-specific differences in the drift trajectories of eggs and yolksac larvae of plaice (Pleuronectes platessa), Atlantic cod (Gadus morhua), sprat (Sprattus sprattus) and horse mackerel (Trachurus trachurus) in the North Sea. In this region, these four species exhibit peak spawning during the boreal winter, late winter/early spring, late spring/early summer, and mid-summer respectively, but utilize the same spawning locations (our simulations included Dogger Bank, Southern Bight and the German Bight). Inter-annual differences in the temperature history, and an increase in the area of dispersion and final distribution at the end of the yolksac phase were more pronounced (and related to the North Atlantic Oscillation) for winter- and early spring-spawners compared to late spring/summer spawners. The progeny of the latter experienced the largest (up to 10-fold) inter-annual differences in drift distances, although absolute drift distances were modest (~2 to 30 km) when compared to those of the former (~ 20 to 130 km). Our results highlight the complex interplay that exists between the specific life history strategies of the different species and the impacts of the variability in (climate-driven) physical factors during the earliest life stages of marine fish. Resumen: Diferencias interanuales e interespecíficas en la deriva de huevos y larvas lecitotróficas en el mar Norte: Aproximación a través un modelo biofísico. – En este trabajo utilizamos un modelo 3-D físico-biológico y un análisis de dispersión del núcleo para investigar las diferencias interespecíficas e interanuales en las trayectorias de la deriva de huevos y larvas lecitotróficas de la solla (Pleuronectes platessa), el bacalao Atlántico (Gadus morhua), el espadín (Sprattus sprattus) y el jurel (Trachurus trachurus) en el Mar del Norte. En esta región, las especies estudiadas muestran distintos picos de distintos desoves en el tiempo: invierno boreal, invierno tardío/primavera temprana, primavera tardía/verano temprano y mitad del verano, respectivamente, aunque comparten las mismas zonas de desove. Las simulaciones efectuadas corresponden a tres de estas zonas: Dogger Bank, Southern Bight y German Bight. Los resultados mostraron diferencias interanuales en la temperatura experimentada por las larvas, en el área de dispersión y en el patrón de distribución al final del estadio lecitotrófico, que fueron más evidentes en el bacalao Atlántico, en comparacion con el espadín. Así mismo, estos factores estuvieron correlacionados con la Oscilación del Atlántico Norte. La progenie del espadín, además, mostró la mayor variación interanual en la distancia de dispersión, siendo hasta 10 veces mayor, aunque la distancia absoluta alcanzada fue relativamente modesta (~2-30 km) en comparación con la observada para el bacalao Atlántico (~20-130 km). Nuestros resultados subrayan la compleja interacción que existe, durante los estadios tempranos del desarrollo de peces marinos, entre las estrategias ecológicas

Beschreibung: We employed a coupled biological–physical, individual-based model (IBM) to estimate spatial and temporal changes in larval fish habitat suitability (the potential for areas to support survival and high rates of growth) of the German Bight, southern North Sea. In this Lagrangian approach, larvae were released into a size-structured prey field that was constructed from in situ measurements of the abundance and prosome lengths of stages of three copepods (Acartia spp., Temora longicornis, Pseudocalanus elongatus) collected on a station grid repeatedly sampled from February to October 2004. The choice of prey species and the model parameterisations for larval fish foraging and growth were based on field data collected for sprat (Sprattus sprattus) and other clupeid larvae. A series of 10-day simulations were conducted using 20 release locations to quantify spatial–temporal differences in projected larval sprat growth rates (mm d− 1) for mid-April, mid-May and mid-June 2004. Based upon an optimal foraging approach, modeled sprat growth rates agreed well with those measured in situ using larval fish ototliths. On the German GLOBEC station grid, our model predicted areas that were mostly unsuitable habitats (areas of low growth potential), e.g. north of the Frisian Islands, and others that were consistently suitable habitats (areas that had high growth potential), e.g. in the inner German Bight. In some instances, modelled larvae responded rapidly (~ 5 days) to changing environmental characteristics experienced along their drift trajectory, a result that appears reasonable given the dynamic nature of frontal regions such as our study area in the southern North Sea.

Beschreibung: An analysis of mass (M) and standard length (LS) data for larval, juvenile and adult sprat (Sprattus sprattus; Clupeidae) revealed marked changes in the allometric scaling factor (b in inline image). For sprat 〈44 mm LS, b was 5·0, whereas in larger juveniles and adults, b was c. 3·4 indicating a relatively protracted metamorphic period for this species.

Beschreibung: Experiments that directly test larval fish individual-based model (IBM) growth predictions are uncommon since it is difficult to simultaneously measure all relevant metabolic and behavioural attributes. We compared observed and modelled somatic growth of larval herring (Clupea harengus) in short-term (50 degree-day) laboratory trials conducted at 7 and 13°C in which larvae were either unfed or fed ad libitum on different prey sizes (~100 to 550 μm copepods, Acartia tonsa). The larval specific growth rate (SGR, % DW d-1) was generally overestimated by the model, especially for larvae foraging on large prey items. Model parameterisations were adjusted to explore the effect of 1) temporal variability in foraging of individuals, and 2) reduced assimilation efficiency due to rapid gut evacuation at high feeding rates. With these adjustments, the model described larval growth well across temperatures, prey sizes, and larval sizes. Although the experiments performed verified the growth model, variability in growth and foraging behaviour among larvae shows that it is necessary to measure both the physiology and feeding behaviour of the same individual. This is a challenge for experimentalists but will ultimately yield the most valuable data to adequately model environmental impacts on the survival and growth of marine fish early life stages. Comparación entre crecimiento observado y predicho de larvas de arenque (Clupea harengus): analizando parametrizaciones de modelos basados en individuos. – Los experimentos que analizan directamente las predicciones de crecimiento generadas por modelos basados en individuos (IBM) son poco comunes puesto que resulta difícil medir simultáneamente todos los atributos metabólicos y conductuales. En este estudio, comparamos el crecimiento somático observado y el estimado a partir de modelos de larvas de arenque (Clupea harengus) en experimentos de laboratorio a corto plazo (50 grados-día) a 7 y 13°en los que las larvas fueron mantenidas en condiciones de ayuno o recibieron alimentación ad libitum con diferentes tamaños de presa (copépodos, Acartia tonsa, de aproximadamente 100 a 500 μm). Las estimas de tasa específica de crecimiento (SGR, % de peso seco por día) fueron, en general, sobreestimadas por el modelo, especialmente para larvas que se alimentaron con presas grandes. estimas del modelo se ajustaron a dos escenarios para explorar el efecto de 1) variabilidad temporal en la alimentación de las larvas, y 2) disminución en la eficiencia de asimilación debida una rápida evacuación del tubo digestivo a tasas de alimentación altas. Con estos ajustes, el modelo describió bien el crecimiento larvario para temperaturas, tamaños de presa y edades de las larvas, indicando que las parametrizaciones metabólicas son robustas. Aunque los experimentos llevados a cabo con grupos de larvas verificaron los modelos de crecimiento, la variabilidad en el crecimiento y conducta de alimentación entre larvas sometidas a las mismas condiciones ambientales ponen de relieve la necesidad de que las medidas fisiológicas y de conducta vayan emparejadas y sean tomadas a nivel individual. Esto representa un reto para los experimentalistas, pero a largo plazo generará datos valiosos para los modeladores encargados de simular efectos ambientales sobre las tasas vitales de estadíos tempranos de desarrollo de peces marinos.