Fish Sampling Techniques

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Description

Hoops nets are a cylindrical or tubular-shaped gear composed of mesh netting supported by a series of typically 4-8 hoops.Internally, the hoop net has one or more “funnels” or “throats” which allow fish movement further into the net but inhibit outward movement (escape).Bait can be hung in the closed end to attract target fish species or groups.Conversely, hoop nets used for sampling fish assemblages may not be baited. 

Type

Passive, entrapment gear

Habitat deployed

Flowing water (rivers), usually in current. If current is slow, then additional staking or anchors may be needed. Mini-hoop nets are used in backwater type habitats having slow current.

Target species

Larger bodied fishes- Catfish (Ictaluridae), Common carp (Cyprinus carpio), Suckers (Catostomidae) including Buffalos (Ictiobus) and blue sucker (Cycleptus elongatus), Freshwater drum (Aplodinotus grunniens), Crappie (Pomoxis spp.), silver carp (Hypophthalmichthys molitrix), Sturgeon (Scaphirhynchus spp.)

Hoop net with seven hoops and two throats

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Typical Sizes, Dimensions, Materials, Mesh size:

• 2’, 3’, 4’, or 6’ diameter hoops
• Hoops can be metal, fiberglass, composite materials, or wood
• All hoops can be the same diameter or slightly decrease towards the cod end
• 7 hoops per net is common
• Net length commonly varies between 10’ – 16’.
• Netting is composed of Nylon or Polyethylene
• Nylon netting is preserved with petroleum-based net coating
• Mesh sizes include 0.5” bar mesh, 0.75” bar, 1.25” bar, 1.5” bar, 2.5” bar
  • The larger the hoop diameter, the bigger the mesh
• A widely used hoop net dimension for scientific sampling is 4’ diameter hoops with 1.25” bar nylon mesh

Overview Introduction

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Hoop Net Dimensions Materials Storage Maintenance

General introduction 1

VIDEO LINK: https://youtu.be/r5JiCs96p9s

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Hoop Net Target Fishes Deployment

General introduction 2

VIDEO LINK:https://youtu.be/Qc8VWUIXQSA

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Hoop Net Overview

General introduction 3

VIDEO LINK: https://youtu.be/CaIcAqzYS54

Materials

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Hoop Net Materials

Hoop net Materials

VIDEO LINK: https://youtu.be/hFbqcFqkKGk

Design Considerations

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Factors Mesh Size

Mesh size

VIDEO LINK: https://youtu.be/d79-S-7cMqM

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Hoop net with four fiberglass hoops, with the mouth on the right and the cod end on the left. In this image, the rear throat is located near the middle of the net and the square throat opening is located between the first and second hoops.

Major categories

• Mini-hoop net- usually has fewer hoops (4) and a throat or funnel is attached to the first hoop at the net mouth.
• Full-sized hoop net- more hoops (5 – 8) and the first funnel should begin at the second hoop from the net mouth; there are usually two throats in a full-sized hoop net, the second throat, often attached on the 4th hoop, is sometimes called the “catch” throat, otherwise the front and rear throats.

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Mini Hoop Net

Mini-hoop nets

VIDEO LINK:  https://youtu.be/KgfI36inPes

Baiting, how hoop nets function, how they catch fish

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Baiting Hoop Nets

VIDEO LINK:  https://youtu.be/cvYYntH1Rpo

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Hoop Net Attraction Technique

VIDEO LINK:  https://youtu.be/Q38pdml95Zc

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How Hoop Nets Catch Fish

VIDEO LINK:  https://youtu.be/btAG1BqCLCw

Issues

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Hoop Net Issues Burying

VIDEO LINK:  https://youtu.be/7dB-6QauJNA

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Hoop Net Issues Detritus Species Interactions

Debris and Negative species interactions: 

VIDEO LINK: https://youtu.be/J1asKAJy-zw

Maintenance

Nylon requires periodic dip or coating treatment typically with a petroleum-based product.

Repair (see also “Repairing Nets” module)

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Hoop Net Repair 1

VIDEO LINK: https://youtu.be/qA5Kv3swCNo

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Hoop Net Repair 2

VIDEO LINK: https://youtu.be/DWOYizF9xBU

Stowage

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Hoop Net Stowage Boat 1

Hoop net storage on boat

VIDEO LINK: https://youtu.be/tL-c-nan-Oc

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Hoop Net Stowage Boat 2

Hoop net storage on boat but bridle too short on the hoop net

VIDEO LINK: https://youtu.be/juWCoJsWX1k

Field Methods, Deployment, Retrieval, Illustrations, and Definitions

Deployment

Usually parallel with the current, closed end (cod) upstream and mouth facing downstream.  Cod end of net attached to a stationary object as an anchor or tree limb, etc.  Mouth of net attached to a float and sometimes also to an anchor.  Flow keeps the hoop net open for sampling.  In slow or still water, both front and rear ends of net may be attached to stakes or anchors.

Hoop net positioned by a stake

Mainstem flowing water

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Hoop Net Deploy Stake

Deployment in moderate current, intermediate-sized hoop net using a stake off cod end

VIDEO LINK: https://youtu.be/X7pRyx-HGB8

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Hoop Net Retrieve Stake

Retrieval in moderate current, intermediate-sized hoop net using a stake off cod end

VIDEO LINK: https://youtu.be/s-9YZgSGNZk

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Hoop Net Deploy Stake 2 floats

Deployment in swift current, intermediate-sized hoop net, using a stake for cod end, double floats

VIDEO LINK: https://youtu.be/tZvQRc4AdKE

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Hoop Net Retrieve Stake 2 floats

Retrieval in swift current, intermediate-sized hoop net

VIDEO LINK: https://youtu.be/VRmM1NkB44U

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Hoop Net Staking Cod End

Deployment in swift current, intermediate-sized hoop net, stake cod end, tie bridle

VIDEO LINK: https://youtu.be/PKiWvVAUxec

Back-eddy (reverse flow)

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Hoop Net Deploy Back Eddy

Deployment in back-eddy (reverse current), intermediate-sized hoop net, anchor and stake selection and use

VIDEO LINK: https://youtu.be/yD9zilqj3DA

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Hoop Net Retrieve Back Eddy

Retrieval in back-eddy (reverse current), intermediate-sized hoop net, cleat assisted removal of stake anchor

VIDEO LINK: https://youtu.be/rcY11Vuof1I

Hoop net positioned by an anchor (in flowing water)

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Hoop Net Deploy Cod Anchor

Deployment in moderate current, using a sand anchor off the cod end

VIDEO LINK: https://youtu.be/kajN1JFvDT8

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Hoop Net Retrieve Cod Anchor

Retrieval in moderate current, using a sand anchor off the cod end, with boat operation techniques, removing catch:

VIDEO LINK: https://youtu.be/CJTBPMi8ZvY

Hoop net held open by an anchor weight (in low-flow conditions)

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Hoop Net Deploy Slow Current

Deployment in slow current areas, large hoop net, using cod end and bridle anchors

VIDEO LINK: https://youtu.be/3RwJbPU0dG4

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Hoop Net Retrieve Slow Current

Retrieval in slow current areas, large hoop net, using bridle anchor, training techniques

VIDEO LINK: https://youtu.be/GykfAVztz2k

Hoop net hidden using drag line instead of a float (in flowing water)

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Hoop Net Deploy Hidden Set

Deployment In moderate current, hidden set, no float, small (2’) hoop net:

VIDEO LINK: https://youtu.be/t94y466V_Qo

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Hoop Net Grapple Hidden Set

Retrieval in moderate current, hidden set, no float, small hoop net boat maneuvering by driver, grappling technique: 

VIDEO LINK: https://youtu.be/AxQNbZtVmBA

Knots Used with Hoop Nets

Bowline, Sheet Bend, Larks Head

Accessory equipment

floats, floating “drag” line, float hook, anchors, stakes, grab, pound pole, gaff

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Hoop Net Anchor Choice

Use of different anchor types (in current): 

VIDEO LINK: https://youtu.be/-kKSdINrLoQ

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Hoop Net Tighten Technique Set 

Detailed methods to set Hoop Net

VIDEO LINK: https://youtu.be/70qg9-TKqdY

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Hoop Net Cleat Assisted Removal

Hoop net stuck in sand, cleat assisted removal

VIDEO LINK: https://youtu.be/bjgcfKol2tc

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Sampling Boat Cleat Requirements

Need for adequate numbers of cleats on boat

VIDEO LINK: https://youtu.be/sS9CvY6eXjQ

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Hoop Net vs Fyke Net

VIDEO LINK: https://youtu.be/Vnaan56VAs8

Definitions:

Anchor: A weight that comes in various configurations used to hold the hoop net in position.  Depending on flow, habitat conditions, or desired level of concealment, tied to the cod line, float line or dragline.

Bridle or Yolk: A line attached to Hoop #1 at mouth.  The float line or dragline attaches to the bridle.  Used to tie hoop net for stowage.

Cod end or pot: Closed or open end opposite the net mouth.  Oriented upstream.  Held closed by a drawstring during sampling and is the net compartment containing most of the captured fish.

Cod line: A line tied to the drawstring on one end and a stationary structure structure
Something temporarily or permanently constructed, built, or placed; and constructed of natural or manufactured parts including, but not limited to, a building, shed, cabin, porch, bridge, walkway, stair steps, sign, landing, platform, dock, rack, fence, telecommunication device, antennae, fish cleaning table, satellite dish/mount, or well head.

Learn more about structure on the other (anchor, stake, woody vegetation). Rode 7:1 recommended (7 feet of cod or anchor line per 1 foot depth of water)

Drawstring: A line tied to the cod end, used to open or securely close the cod end.

Float: Floating object that can come in a variety of shapes and sizes, attaches to the float line. Used for aiding location and retrieval.

Float line or dragline: A floating line tied to the bridle and terminating in a float (= float line) or an anchor (dragline). Can be flat-shaped to aid in retrieval and made of polyethylene.

Hoop: Made of metal, fiberglass, or composite materials. Hoops are the supporting structure of a hoop net.  Common diameters are 2’, 4’, and 6’.  All hoops can be equal diameter in a hoop net or taper toward the cod end.

Mesh: Usually built of nylon but sometimes polyethylene. Comes in various bar mesh sizes, such as 0.5”, 1.25”, 2.5”.  If nylon, the mesh must be dipped in a coating for preservation.

Mouth: Opening to the hoop net, hoop #1. Oriented downstream.

Pound pole: A rod, hollow on one end, typically made of fiberglass and metal, but also wood or aluminum, used to pound stakes into the substrate.

Stake: A metal rod tied to the cod line and pounded into the substrate to hold the hoop net in position.

Throat: Mesh material in a cone or funnel shape, having a larger opening toward the mouth and a smaller opening toward the cod end. The throat is held in position by lines tied to posterior hoops or the cod end.

            Types

            Square- the throat has a square-shaped exit hole; square throats are sometimes used for the front throat to make the net mouth appear more open

            Finger or Crow’s Foot- the throat has a somewhat flat exit, and the “fingers” are lines tying the throat exit to a posterior hoop.

            Flat- the exit is very flat since the exit is tied by essentially right-angles lines to the close hoop, thereby stretching and flattening the throat exit