The influence of different salinity conditions on egg buoyancy and development and yolk sac larval survival and morphometric traits of Baltic Sea sprat (<i>Sprattus sprattus balticus</i> Schneider)

Abstract

SUMARY:The small pelagic sprat (Sprattus sprattus) is a key ecologic player in the Baltic Sea. However, there is longterm variability in recruitment which is thought to be influenced by fluctuations in abiotic and biotic conditions experienced during the early life stages. This study concentrates on the influence of different ambient salinities on sprat egg development, egg buoyancy and survival as well as early yolk sac larval morphometric traits. Egg buoyancy significantly decreased with increasing salinity experienced during fertilization and/or incubation experiments. Field egg buoyancy measurements in 2007 and 2008 exhibited annual and seasonal differences in specific gravity, potentially associated with changes in adult sprat vertical distribution. Neither egg development time nor the duration of the yolk sac phase differed among salinity treatments. At eye pigmentation, larval standard length exhibited high variance among individuals but did not differ among treatments. The largest ecological impact of salinity experienced during spawning was the modification the buoyancy of eggs and yolk sac larvae, which determines their vertical habitat in the Baltic Sea. There are strong thermo-and oxyclines in the Baltic Sea, and thus salinity can indirectly impact the survival of these early life stages by modifying the ambient temperatures and oxygen conditions experienced.Keywords: clupeids, vertical distribution, specific gravity, drift, recruitment, spawning stock, adult fish. RESUMEN: INFLUENCIA DE DIFERENTES CONDICIONES DE SALINIDAD EN LA FLOTABILIDAD DE LOS HUEVOS, DESARROLLO Y SUPERVIVENCIA DE LARVAS LECITOTRÓFICAS, Y RASGOS MORFOMÉTRICOS DEL ESPADÍN DEL MAR BÁLTICO (SPRATTUS SPRATTUS BALTICUS SCHNEIDER). -El espadín (Sprattus sprattus)es un pequeño pelágico que juega un papel ecológico clave en el mar Báltico. No obstante, se considera que la variabilidad a largo plazo en el reclutamiento está influenciada por condiciones bióticas y abióticas experimentadas durante los primeros estadios de desarrollo. Este estudio se concentra en la influencia de diferentes salinidades ambiente sobre el desarrollo de los huevos de espadín, su flotabilidad y supervivencia, así como sobre los rasgos morfométricos de las larvas lecitotróficas. La flotabilidad de los huevos disminuye significativamente con los incrementos de salinidad experimentados durante los experimentos de fertilización y/o incubación. Las medidas de flotabilidad en el medio mostraron diferencias en la gravedad específica de carácter anual y estacionales en 2007 y 2008, potencialmente asociadas a cambios en la distribución vertical de los adultos de espadín. Ni el tiempo de desarrollo de los huevos ni la duración de la fase lecitotrófica difirió entre los tratamientos de salinidad. En el estadio de pigmentación de los ojos la longitud estándar de las larvas mostró importante variabilidad entre individuos, pero no entre tratamientos. El mayor impacto ecológico debido a la salinidad experimentada durante la puesta fue la modificación de la flotabilidad de los...

Trait structure and redundancy determine sensitivity to disturbance in marine fish communities

“…For example, trait structure and redundancy are intrinsically correlated with environmental conditions, and we found that sensitivity was also related to environmental change in both ecosystems. In the EEC, salinity changes may have contributed to declines in species with small pelagic eggs and larvae, as salinity influences egg buoyancy and survival (Nissling, Nyberg, & Petereit, ; Petereit et al, ; Sundby & Kristiansen, ). However, salinity changes in the EEC were much lower than those normally reported to impact fish community structure (Petereit et al, ; Sirot et al, ).…”

“…SST is a primary driver of species’ distributions and abundances globally, and SST warming can profoundly impact marine fish communities, which are highly responsive to changes in temperature (Simpson et al, ). Salinity can influence community structure through physiological responses, impacts on larval success, and shifts between stenohaline and euryhaline species (Petereit et al, ; Sirot et al, ). Although chlorophyll‐ a can also determine community structure through bottom‐up control and through larval success and recruitment (Beaugrand, ; Capuzzo et al, ), spatially resolved data for chlorophyll‐ a were not available prior to 1998.…”

Temperature effects on vital rates of different life stages and implications for population growth of Baltic sprat

“…It has to be noted that a synchronous warming of all water layers as simulated in this study is probably not a realistic scenario. It is more likely that changes in water circulation and vertical mixing will profoundly affect stratification dynamics and oxygen supply to the deep basins, which may also affect survival and growth of sprat early life stages (Petereit et al 2009;Voss et al 2011). Besides warming, a number of other physical processes will be impacted by climate changes that have been correlated with sprat survival.…”

“…A future warming scenario, as predicted by the IPCC (2007), is likely to affect all depth strata in the Baltic, and hence all life stages of sprat, since the turnover rate of the entire water body in the deep basins of the Baltic is comparatively high (Meier 2005). In addition, increased precipitation within the Baltic watershed in combination with less frequent inflow events of more saline North Sea water is predicted to lower salinities (Meier 2006), which will in turn affect the vertical distribution of and hence ambient temperature experienced by sprat early life stages (Petereit et al 2009). …”

Floating along buoyancy levels: Dispersal and survival of western Baltic fish eggs

“…After a settling time of 60 min, the position of every single egg in the salinity gradient column was recorded to calculate the respective density value. This general method has been regularly applied to measure fish egg density (neutral egg buoyancy) for various Baltic fish species including cod, sprat and flatfish from other areas of the Baltic Sea (Nissling et al, 1994(Nissling et al, , 2002Petereit et al, 2009). We used density gradient columns similar to the setup described by Coombs (1981) and Coombs et al (1985).…”