From: Roy Drinnan <rdrinnan@netcom.ca>
To: AQUA-L@LISTSERV.ifmt.nf.ca
MORTALITY OF BIVALVE LARVAE
COMMENTS 1: (see "Gas bubble disease and ingestion of gas bubbles in fish larviculture", NL 27)
I never knew that atmospheric conditions can cause
supersaturation at shallow depths. This may be an additional reason for why survival rates of bivalve larvae in large (deep) containers is much higher than in beakers (the other reason is that larvae in large containers do not bump into the sides as often).
Madelon Mottet, Ph.D.
Alaska-Southeast Bio-Research
704 sawmill Creek Blvd.
Sitka, Alaska 99835 USA
madelon@ptialaska.net
Tel/Fax (907) 747 3862
*******
COMMENTS 2:
I would suggest that neither of the factors you suggest are the
major one causing the container-size effect in bivalve larval rearing. I
started 45 years ago using 1 liter beakers and have since used a wide
variety of containers up to 1,000 l. As have many others, I found a general correlation between container size and larval survival. I suggest that this is due largely to bacterial contamination, this being proportional to the ratio of area of container wall surface to container volume. In my experience anti-bacterial technologies (u/v water sterilisation, use of antibiotics or bactericides and sanitation and frequent water changes) can virtually remove the effect. I must admit that I have no specific data on bacterial counts to support the hypothesis.
I have also never found supersaturation to have any effect on larvae!
Roy Drinnan E-mail: rdrinnan@netcom.ca
RR#1 Musquodoboit Harbour Phone: (902) 889-3432
Nova Scotia, Canada, B0J 2L0 Fax: (902) 889-2905
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