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Richard:
You have asked some very interesting questions, which to my knowledge are
totally unanswered at this point. First of all, is the Mola mola really a
weak swimmer? I have observed some tremendous acceleration by large molas
when released from capture, which indicates that at least for short bursts
molas can be powerful swimmers. However, in order to adequately quantify
movement patterns, two telemetry studies are presently underway. One will
use pop-up satellite tags to ascertain long term movements – hopefully this
study will give us some better insight into seasonal migration. Another
study, at Cal State Long Beach, is using acoustic telemetry to determine
depth and temperature preferences of these fish, as well as fine-scale
short-term movement patterns. Between these two studies a great deal of
information should be available, but you may have to wait a year or two!
Temperature tolerance is another interesting question. If these animals
are in fact going below the thermocline while foraging for prey, perhaps the
basking behavior which we see so often (and which you seem to have observed
in the English Channel) is a thermoregulatory response to the low
temperatures encountered while foraging. Again, the acoustic telemetry
being done will give us some more insight into this phenomenom.
I’m in the field presently, and don’t have access to any literature, but
if memory serves me there is a paper by F. Schwartz published in the journal
of the Elisha Mitchell Society which talks about seasonal movement of this
species – I don’t remember the date…
Another paper which may be of interest to you is published in Copeia – the
name of the author eludes me but it is quite an old article, possibly
written in the 40’s. This article describes seasonal movements of Mola mola
into Monterey Bay, California, presumably following large concentrations of
jellyfish.
Dan Cartamil
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Dan Cartamil; Graduate Student, Teaching Associate
Dept. of Biology
California State Univ.,
1250 Bellflower Blvd.
Long Beach, CA 90840
Office Phone: (562) 985 - 4918
Home Phone: (562) 961 - 8448
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I was speeding across the English Channel from Guernsey to Poole Harbour, UK
last Friday when I saw my first oceanic sunfish, Mola mola, of the year
gently waving its dorsal fin just north of the South bound shipping lane. A
few compass jellyfish, Chrysaora hysoscella, have washed up on Guernsey
beaches during the last month. I do not know if the Mola mola schools
follow concentrations of these jellyfish up the English Channel.
I am curious as to how a weak swimmer such as the Mola mola swims into
northern latitudes during the latter part of the summer and then presumably
retreats south with the onset of colder weather. Does the oceanic sunfish
undergo vertical migrations to use ocean current transport? Has someone on
this list studied the migrations of Mola mola? Does anyone know the
temperature tolerances of Mola mola? I have seen large schools of Mola mola
off New York, USA during the summer months. Where do the schools of Mola
mola from the Eastern and Western Atlantic go during the winter months? Do
these fish go south for the winter? Thank you for any insights.
Yours sincerely,
Richard
Richard Lord
Guernsey GY1 1BQ
Great Britain
Email: [log in to unmask]
Tel: +44 (0)1481 700688
Fax: +44 (0)1481 700699
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