While collecting fishes in Mexico, in the Mizol Ha River, daylight
collecting proved frustrating and only marginally successful. It was
impossible to capture any of the livebearers for instance, as they proved to
be sly about seeking cover in the roots and branches of trees that had
fallen into the river. They never strayed far from this cover. You could
observe them easily with mask and snorkel, and if you were willing to remain
still, they would even venture forth to pluck at the hairs on your arms and
hands, but the slightest movement would cause them to vanish. Also, the
cichlid species were difficult to approach as well.
Upon returning to the river at night, and using snorkeling gear again, and
aided by head lamps (water-proof of course), we discovered that all the fish
that had proven impossible to capture were now lying dormant among the
cobble. It was easy to swim above the animal, and dive down to it. Once
there, a tiny aquarium net was all that was needed. Simply place the net
over the sleeping fish, and there you had it. Complete success.
Also, the catfish that had proven to be elusive during daylight were out in
force. They were still hard to capture, but there were so many of them that
repeated attempts proved fruitful.
I haven't done anything similar in the States (diving that is), but night
collecting with a seine always has proven to be worthwhile. I particularly
find that night collecting is easier on the fish in the summer months, when
the difference between daytime air temperatures and water temperatures is so
great that fragile species such as redside shiners quickly expire.
Collecting at night during the summer decreases such mortality, as the air
temperature has diminished.
Another benefit to night collecting in the summer is the lack of personal
watercraft threatening your safety.
Norm
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----- Original Message -----
From: Jay DeLong <thirdwind_at_att.net>
To: <nanfa_at_aquaria.net>
Sent: Wednesday, July 12, 2000 6:03 PM
Subject: RE: NANFA-- collecting at night
Dave Neely said:
> but night collecting/snorkelling is in my experience MUCH more
> effective for madtoms and some large darters (eg, Crystallaria,
> Percina shumardi).
How about sculpins, Dave? A few years back I conducted a research project
on the mottled sculpin's habitat preferences in a stream in South Carolina.
All my field work was conducted during daylight hours. I always found the
fish associated with protective cover and generally in shallow water of
moderate velocity. While doing some reading on the fish I found that it is
a nocturnal feeder. I wonder where that fish roams at night?
-- Jay DeLong Olympia, WA
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