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Dear David,
Since nothing is known of Engraulicypris sardella spawning substrate or
habitat try using a long-line of various spawning substrates (bundles of
various fibers or sticks, mop heads, or even concrete blocks, and clay
flower pots) set at different depths. Most adhesive eggs adhere fairly well
to the spawning substrate so pulling them slowly up from depth should not be
a problem.
Rick Nemeth
At 11:16 PM 3/14/99 +0000, you wrote:
>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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