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David,
Have you tried spawning the fish yourselves? This works well with herring,
which also have sticky negatively buoyant eggs. For a study I was
involved with we simply took ripe females, encouraged some eggs out with
belly rubs, spread them onto glass slides with a butter knife, and added
milt. We could then observe them develop conveniently.
-----Original Message-----
From: David John Hutchinson <[log in to unmask]>
To: [log in to unmask] <[log in to unmask]>
Date: Sunday, March 14, 1999 3:26 PM
Subject: Re: Sticky fish eggs (fwd)
>To anyone tht can help:
>>
>> I'm interested in collecting samples of eggs from a fish that is known to
have sticky, negatively buoyant eggs,
>but
>> whose spawning site is not known. The constraints are that the possible
spawning areas are likely to be deep
>> (>50 m < 200 m), and the substrate unknown, plus we are not likely to
have access to substantial benthic
>grabs.
>> How do we sample the eggs? Someone suggested coconut fibre matting, to
which the eggs whould adhere. I'm
>> concerned that hauling doormats up from depth would flush out any eggs,
unless they really were
>super-adhesive.
>> Can anyone suggest an ACME deep benthic fish-egg sampling device?
>>
>> For those curious about this mystery fish, it is Engraulicypris sardella
from Lake Malawi. Previously thought to
>> have pelagic eggs, intensive surveys done a few years ago (reported in
Thompson, A.B. 1996 J. Plankton Res.
>> 18: 1349-1368) found few eggs but many newly hatched larvae. The
conclusion drawn from this and previous
>> studies was that pelagic eggs are unlikely - (discussion in Thompson, p
1363). Reviewing cyprinid life-histories
>> suggests the same conclusion. Similarly, if E. sardella spawned in
shallow waters, local fishermen would know
>> about it. We have surveyed 'indigenous knowledge' on possible spawning
sites, and the indications from
>> fishermen are that the sites are deep in the parts of the lake where
there are strong currents, but they admit to
>not
>> knowing for sure.
>>
>> As this fish supports one of Malawi's most important fisheries, finding
its spawning habitat is interesting from the
>> applied point of view, as well as contributing knowledge to the life
history strategies of tropical cyprinids.
>>
>many thanks,
>
>David
>
>David Hutchinson
>School of Biological Sciences
>University of East Anglia
>Norwich
>NR4 7TG
>UK
>
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