Table 1. Fish Species with High and Low Potential for Retaining Gastrically Inserted Transmitters as Adapted from Nielsen (1992)

ERDC TN-DOER-E18

February 2005

an underwater 35-mm camera. In forced ingestion, the tag is pushed into the stomach with a

glass or plastic rod. The tag is usually lubricated with glycerine or other suitable product. Tagged

fish are generally marked so commercial and sport fishermen can return tags (usually only

necessary if an archival tag is used). If radio transmitters are used the tag wire is typically fed

back through the gill slits and allowed to trail freely in the water. Forced insertion of acoustic

tags was used on 29 pre-spawning adult American shad as part of a pilot study on the York

River, Virginia (Olney et al. 2004). All but two tagged fish were successfully detected at upriver

spawning grounds.

A chief concern with stomach-inserted or ingested transmitters is loss of a tag through

regurgitation or egestion. Regurgitation rates vary greatly, depending on the fish species and the

relative size of the tag (Nielsen 1992). Table 1, adapted from Nielsen (1992) lists species with

high and low potential for retaining gastrically inserted radio and acoustic transmitters.

Table 1

Fish Species with High and Low Potential for Retaining Gastrically Inserted

Transmitters as Adapted from Nielsen (1992)

Species Likely to RegurgitateTag

Species Unlikely to Regurgitate Tag

American shad

White sucker

Alosa sapidissima

Catostomus commersonni

American eel

Northern pike

Anguilla rostrata

Esox lucius

Brown bullhead

Atlantic cod

Ictalurus nebulsus

Gadus morhua

White bass

Skipjack tuna

Morone chrysops

Katsuwonus pelamis

Striped bass

Coho salmon

Morone saxatilis

Oncorhynchus kisutch

Pink salmon

Rainbow trout

Oncorhynchus gorbuscha

Oncorhynchus mykiss

Chum salmon

Yellow perch

Oncorhynchus keta

Perca flavescens

Sockeye salmon

Atlantic salmon

Oncorhynchus nerka

Salmo salar

Chinook salmon

Brown trout

Oncorhynchus tshawytscha

Salmo trutta

Bluefin tuna

Sauger

Thunnus thynuus

Stizostedion canadense

Oviduct insertion has been used successfully with salmonids. Transmitter wires were allowed to

freely trail from the oviduct. Some studies reported expulsion of the tag within 7 to 13 days,

although Peake et al. (1997) reported retention longer than 14 days and up to 60 days for 70 percent

of tagged fish. They also reported that this technique might be suitable for sturgeon

(Acipenseridae) as well as several other taxa.

Another common method of internal tagging is intra-peritoneal surgery, which has been used

successfully for the past 20 years with several species of marine and freshwater fishes. In this

technique, a small incision is made in the body wall of the fish with a sharp scalpel. Mid-ventral

incisions are more commonly used than lateral incisions, reducing the chance of damage to the

internal organs, while decreasing the time necessary for healing of the wound. Incision length

should be as short as possible, but is determined by tag length and diameter. Shorter incisions

typically have less risk of tag expulsion and shorter healing times. Incisions are typically closed

with sutures or surgical staples. Surgical stapling is a quicker method of incision closure, but

requires removal of more rows of scales, which could lead to greater risk of infection. This

method of tagging requires adequate training of personnel to reduce injury and mortality to

tagged individuals.