Dataset: shrimp nets with kites_bycatch
Deployment: NEC-PH2003-1

Use of Kites in Shrimp Codends to Reduce Small Shrimps and Bycatch Species

Principal Investigator:

Dr Pingguo He (University of New Hampshire, UNH/OPAL)

Co-Principal Investigator:

Dr Daniel Schick (Maine Department of Marine Resources, Maine DMR)

Captain:

Vincent Balzano

Proctor Wells

Project:

Northeast Consortium: Cooperative Research (NEC-CoopRes)

Data URL:

https://osprey.bco-dmo.org/dataset-deployment/452668/data

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Description

This project was to test an assumption that codend meshes expended by water-borne kite would allow more small shrimps and finfish to escape from the codend. A full scale kite-assisted shrimp trawl codend was tested in a flume tank to determine kite size, number of kites, their position and installation on the codend. The resulting full scale codend was tested at sea for the pink shrimps in Gulf of Maine shrimp trawl fishery through comparative fishing using the two-vessel parallel tow method. Seventy-seven pairs of tows were completed on two rigging designs. The results did not support the assumption that codends expanded by water-borne kites would reduce finfish and small shrimp catch in the fishery. Catch and bycatch data collected throughout sea trials showed that a significant amount of fin fish bycatch still exists in the fishery even with the use of the Nordmore Grid. This is especially true for whiting for which a large amount of catch was discarded late in the season. This result indicates a need for continued effort in research and development for a better shrimp trawl to minimize bycatch in the pink shrimp fishery.

Final report

Methods & Sampling

Dataset acquisition description

Target species "shrimp" Pandalus borealis; other shrimp species caught: Pandalus montagui, Dichelopandalus leptocerus

Kite and codend design. The kites used in the codend cover were 2'6" by 1'3" and 1'3" high trapezoids made of rubberized canvas (He et al., 2005; He, 2007). The kite was restrained by a 16" twine to form an arc shape to ensure expanding in the correct direction.The codend used was the same size as the commercial shrimp codend. Shorter gore rope or lastridge ropes, were installed on the gore of the codend to take the strain of the load in the codend during the second half of the sea trials. Eight kites were used in each codend. The number and the position of the kites were determined by flume tank tests as described below.

Flume tank tests. A full scale codend with the last belly section of the trawl and the Nordmore Grid was shipped to the Newfoundland flume tank for testing in December 2003. Kites were installed onto the codend by the engineer at the flume tank with assistance from the project team members. Industry partners, the scientific collaborator and the principal investigator participated in flume tank tests.

Fully-rigged codend with kites and the Nordmore Grid was shipped back to industry partners for sea trials. Another codend identical to the one tested was constructed by a local gear manufacture for the other vessel.

Sea trials. Sea trials were carried out during the 2004 shrimp season between February and May off the coast of Maine. An exempt fishing permit was obtained from the State of Maine to fish out of the shrimp season during the late part of sea trials. Two vessels were involved constituting parallel tows, comparing catch and bycatch of shrimp codends with and without kites. Vessels owned and operated by industry partners were used for the sea trials. F/V 'Tenacious' based in Phippsburg (ME) and operated by Proctor Wells, and F/V 'North Star' based in Portland (ME) and operated by Vincent Balzano were fishing side by side during sea trials.

The two vessels had a similar shrimp trawl (880 mesh fishing circle) and compatible trawl doors (Bison #7). The bridles between the door and the wingend were 85'. Similar 12' Rockhopper sweeps were used by both vessels. The two vessels performed comparative fishing using the parallel tow method. While one vessel was towing a codend with kites, the other would be towing a regular codend without kites. The codend was switched after fishing for not more than two days. The tow duration was one hour and the towing speed was 2.4 knots.

The sea trials were divided into two sessions, with modification to the gear made at the start of the second session. During comparative fishing between the two vessels, the vessels stayed within 1/4 nautical miles from each other. The codend was switched from 'with kites' to 'no kites' in one vessel, while from 'no kites' to 'with kites' in the other vessel, or vice versa. During the second session of the sea trials, starting from Tow 35, modifications to the codend included shortened gore rope which was 7% shorter than the fully stretched codend length. Six tows were completed with both vessels towing a codend with kites at the same time to examine if there was any difference between the two codends with kites. The 'calibration' tows were carried out at the middle of the sea trial period. An underwater video camera and acoustic measurement devices will be used to monitor the functioning of the shrimp trawl codend with kites. A video camera was installed above the codend in a number of times to monitor the fish/shrimp escaping from the codend (exhibit 4). The NetMind' trawl measuring device was used to monitor trawl geometry.

Data Processing Description

Dataset Processing Description

Sampling, measurement and analysis. The total shrimp catch was weighed. A sample of about 1 kg shrimp from each tow from each vessel was sent to the Maine Department of Marine Resources' (DMR) Boothbay Harbor laboratory for further measurement and examination. Catches were divided into four categories during analysis: target species - shrimps, and bycatch species including controlled species, other species, and shellfish (Exhibit 5). All controlled groundfish bycatch was separated and their lengths measured. A sub-sample was measured in cases when large number of bycatch species were retained. Some dominant species in the 'other fish' category were also sampled and measured. All catches were weighed according to species.

Shrimp sizes were evaluated by measuring the carapace length and determining the 'count' which is the number of shrimp per pound. Shrimp samples sent to DMR were measured (for carapace length), and examined (sex, sexual stage, and whether egg bearing). Three species of shrimps were identified in the shrimp samples and their were separately recorded. Paired t-test was used to evaluate differences of shrimp catch, bycatch of controlled and other species, and shrimp size (count) between codends with and without kites.

More information about this dataset deployment

Funding

Award Number	Funding Source
unknown NEC-CoopRes NOAA	National Oceanic and Atmospheric Administration

Instruments

Beam Trawl

Supplied Name: Trawl

Supplied Description:

modified shrimp trawl

Instrument Type

Generic Name: Beam Trawl

Acronym: Beam trawl

Community Identifier: http://vocab.nerc.ac.uk/collection/L05/current/24/

Generic Description:

A beam trawl consists of a cone-shaped body ending in a bag or codend, which retains the catch. In these trawls the horizontal opening of the net is provided by a beam, made of wood or metal, which is up to 12 m long. The vertical opening is provided by two hoop-like trawl shoes mostly made from steel. No hydrodynamic forces are needed to keep a beam trawl open. The beam trawl is normally towed on outriggers, one trawl on each side.

While fishing for flatfish the beam trawl is often equipped with tickler chains to disturb the fish from the seabed. For operations on very rough fishing grounds they can be equipped with chain matrices. Chain matrices are rigged between the beam and the groundrope and prevent boulders/stones from being caught by the trawl. Shrimp beam trawls are not so heavy and have smaller mesh sizes. A bobbin of groundrope with rubber bobbins keeps the shrimp beam trawl in contact with the bottom and gives flatfish the opportunity to escape.

Close bottom contact is necessary for successful operation. To avoid bycatch of most juvenile fishes selectivity devices are assembled (sieve nets, sorting grids, escape holes). While targeting flatfish the beam trawls are towed up to seven knots, therefore the gear is very heavy; the largest gears weighs up to 10 ton. The towing speed for shrimp is between 2.5 and 3 knots.

(from: http://www.fao.org/fishery/geartype/305/en)

Parameters

Supplied Name	Supplied description	Supplied Units	Standard Name
link	This is a link to the README file and Excel data files.	text	external_link

Database

Contribute Data

Dataset: shrimp nets with kites_bycatch
Deployment: NEC-PH2003-1

Dataset acquisition description

Dataset Processing Description

Database

Contribute Data

Dataset: shrimp nets with kites_bycatchDeployment: NEC-PH2003-1

Dataset acquisition description

Dataset Processing Description

Dataset: shrimp nets with kites_bycatch
Deployment: NEC-PH2003-1