JELNET Protocol for Broad-scale Cruises
Please Be Gentle.
This Net System is Designed to Quantify
- Tows to be made at all Priority 1 stations, weather permitting. At
Priority 1 stations where a 10 m MOCNESS trawl is NOT made because of
weather conditions, we would especially like the JelNet tow to be made,
since it would then be the only sample for large jellies.
- Tows are vertical, made from the depth of the deepest MOC-10 net,
(usually 0-15 m off the bottom) or to 100 m at the deeper stations. It is
not necessary to use a flowmeter with these tows; we will calculate volume
filtered from mouth diameter and depth. Suggest the winch operator zeros
the wire out when the net is at the surface. The wire out, and not the
target depth, is the distance value logged at sea and then used
to compute the seawater volume filtered by the net.
- The net may be cast at 20 meters a minute, while it should be
retrieved at no more than 5 m/min. Do not allow the net to rest at
the surface when retrieving the net because the ship's roll may act to
spill a portion of the catch.
- Getting the catch out of the net: Lean the frame on it's edge and
gently rinse the catch down into the codend bucket.
- Carry the bucket into the wetlab, and place the catch in the
transparent tray and view on the light table. Since much of the cast may be
fragile (large ctenophores, etc.), it need be examined immediately, before
preservation. We would like a count of the large jellies, particularly
lobate ctenophores (i.e. Bolinopsis, Mnemiopsis), and an oral /
aboral length measurement of all the animals of a given taxa, or a
subsample of ten measurements if there is more than ten individuals within
a given taxa. Measurements are made with a ruler from underneath the dish.
The entire catch should then be preserved in a liter jar in 10% buffered
- Label jar and
Please keep these samples in a
Contact Erich Horgan
(email@example.com or 508-289-3207) for further details.
Note: prior to the 1999 field season, the
Net Protocol was used.
February 17, 1999 - Erich Horgan