The effects of saline
environments on survival and growth of eggs and larvae of Chirostoma
estor estor Jordan 1880 (Pisces: Atherinidae)
C.A. Martνnez-Palacios, J.C. Morte, J.A.
Tello-Ballinas, M. Toledo-Cuevas, L.G. Ross-2004
Aquaculture, 238: 509-522
Abstract:
Pescado blanco, Chirostoma estor estor, is a
species unique to certain Mexican altiplano lakes and is under severe
environmental and fishing pressure, to the point of becoming endangered. C.estor
estor is now part of a programme designed to develop aquaculture
technology for the species which will preserve biodiversity, enable
restocking and provide a basis for semi-intensive aquaculture. Although now
fully adapted to freshwater, members of the genus Chirostoma are
derived from estuarine or coastal ancestors many of which are euryhaline.
This paper describes investigations of salinity tolerance in C. estor
estor, designed to improve hatchery strategies and hence survival and
growth.
Eyed egg development was high in freshwater, maximal
at about 10, and then significantly reduced at higher salinities. Saprolegnia
infection rate was very high in freshwater, but reduced markedly at 5 and
was abolished at higher salinities. Hatching success was greatly increased
by rearing eggs in moderate salinities, but allowing hatching to take place
in freshwater. This may be related to inhibition of activity of chorionase
or mobility of the larvae at higher salinities. Instantaneous transfer of
larvae to a range of salinities resulted in very high mortalities above
10. Following 48-h acclimation to salinities up to 15, maximum
survival rate over 30 days was obtained at 10. In terms of survival,
optimum practice would be for egg development to occur at 10, hatching to
occur at 5 and subsequent development to take place at 10. Growth in
dry weight over 30 days was greater at 10 and 15 and was significantly
greater than that recorded at 0 and 5. Overall, the results reveal the
euryhaline capabilities of the species, and this can clearly be related to
an estuarine or coastal ancestry, from which the species group radiated
relatively recently. The implications and advantages of using saline
environments for optimal husbandry of eggs and early larvae are discussed.