Salinity tolerance in young Allis shad larvae (Alosa alosa L.)

Abstract

Bardonnet A, Jatteau Ph. Salinity tolerance in young Allis shad larvae (Alosa alosa L.).Abstract -Estuarine migration in Allis shad (Alosa alosa) usually does not take place before mid-summer, but exposure to salinity in brackish water may occur earlier as many spawning areas are of necessity located in upper estuarine zones due to the placement of dams. Therefore, Allis shad conservation programmes need to consider the risk of mortality due to the ability of young Allis shad to tolerate salinity. To evaluate larval mortality due to the inability of larvae to withstand salinity during early ontogeny, we exposed larvae of different ages (from few days old to 27 days old) to salinities ranging from 0 to 30 gAEl )1 . Results indicate that direct seawater exposure induces high mortality in young larvae whatever the ontogenetic stage. However, young larvae can easily deal with upper estuary salinity conditions.

Estuarine phase during seaward migration for allis shad Alosa alosa and twaite shad Alosa fallax future spawners

“…2007). The other shows very good survival of fish from 5–8 days to 27 days posthatching at salinity 10 g·l −1 (Bardonnet & Jatteau 2008). Both studies clearly indicate that allis shad could be found in the upper‐middle estuary younger than 58 days of age, the age at which the first emigrant enters the estuary according to the present study.…”

Effects of temperature, salinity and feeding frequency on growth and mortality of twaite shad (Alosa fallax) larvae

“…larvae abundances observed by Esteves and Andrade (2008) in the oligohaline and mesohaline sections of the Guadiana estuary support these results. However, A. fallax larvae presented clear differences in salinities optimum relatively to other Alosa spp., with A. alosa and A. sapidissima larvae optimum closer to 10 g·L −1 (Limburg and Ross, 1995;Bardonnet and Jatteau, 2008). The observed salinity optima differences for larvae growth and survival could result from species specific physiologic development.…”

“…Leach and Houde, 1999;Jia et al, 2009) and European Alosa species (e.g. Aprahamian and Aprahamian, 2001;Bardonnet and Jatteau, 2008). Young A. fallax larvae were able to withstand environments with salinities ranging from 0 g·L −1 up to 15 g·L −1 , thriving at 2.5 g·L −1 while being unable to survive at 20 g·L −1 .…”

“…Alosa fallax mainly spawns in tidal freshwater, where both eggs and young larvae may passively drift to oligohaline and mesohaline environments (Caswell and Aprahamian, 2001;Esteves and Andrade, 2008). During the downstream drift, larvae face an increasing salinity gradient that can exert a significant environmental pressure when functional osmoregulation is not yet fully developed (Limburg and Ross, 1995;Bardonnet and Jatteau, 2008). In fact, young Alosa spp.…”

“…However, distinct methodological approaches were used between the current study and others previously mentioned. For instance, Bardonnet and Jatteau (2008) analyzed different larval stages and had a different experimental set regarding exposure time and salinity ranges.…”