Should fin clipping be used as a method for identification of fish? Authors

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Should fin clipping be used as a method for identification of fish?

This paper is a compilation of groupwork provided by the following participants on a course in Laboratory Animal Science at the Norwegian School of Veterinary Science, February 2011:

Tommy Berger Eriksen, Thomas Fraser, Håkon Gregersen, Mads Kristiansen, Marianne Olufsen, Binoy Rajan, Raul Ramirez, Jareeporn Ruangsri, Øyvind Røn & Michel Guarjardo Sarmiento.
The groupwork was compiled into one document by Adrian Smith, Norecopa ( Norecopa offers this compilation as a service to researchers, but does not necessarily endorse its content.

Individual identification methods are commonly used in fish research, including studies on size of stocks, growth rates, migration patterns, behaviour and genetics. In aquaculture, such methods can be used to calculate growth rates and to aid identification of fish that have escaped.
Fin clipping has often been used in breeding programs, since it is an approved method (Landbruks- og matdepartementet, 2009). Since these programs employ large numbers of fish and are carried out over a long period, it is possible to observe any effects on growth and survival as an effect of fin clipping (Hansen, 1988).
Various types of fin clipping have been the subject of research. Studies on the effects of total or partial removal of different fin types have been conducted on many different species, although the majority have been performed on salmonids.
Criteria for marking methods
A good marking method must meet several requirements:

  1. It must be legal

  2. It should have minimal effects on the fish

  3. It should be easy to read

  4. It should last sufficiently long for the duration of the study period

  5. It must be suitable for the specific situation.

Most often, a compromise between these requirements is unavoidable when using one single method.
Legal requirements

The Norwegian Animal Welfare Act states (§9):

Medical and surgical treatment shall be carried out taking into account the animal’s welfare, and protect the animal’s ability to function and its quality of life.

Surgical procedures or removal of body parts must not be carried out unless there is a justifiable reason to do so out of consideration for the animal's health. Marking of animals in holdings is nevertheless permitted*. The removal of horns and castration is permitted when it is necessary for animal welfare reasons, or other specific reasons. 

In the case of painful incision, necessary anaesthetic and pain relief shall be used.
*In the original Norwegian version of this sentence, the phrase ‘forsvarlig merking’ is used, i.e. marking is only permitted when using techniques that are defensible.

Types of fin clipping
The fins most commonly subjected to clipping are the adipose fin and pelvis fins, but clipping of the tail fin, pectoral fin, dorsal fin and anal fin has also been tested. The method consists essentially of clipping a fin in a standard pattern with scissors, trying to make the same cut/shape in all fish of the same family group.

Fin clipping has been used to recognize individuals within a group and is commonly used in breeding work and animal tracking in the field (Gunnes & Refstie, 1980). In breeding programs, fish are often tagged as soon as they reach sufficient size (5-10 grams), using a characteristic clip for each family. This method is suitable for situations where there are only members of a few different families that need to be identified afterwards.

Advantages and disadvantages of fin clipping
Fin clipping is the most common method for marking groups of fish, but there is still debate in the scientific community as to whether it causes harm. The majority of research studies conclude that fin clipping does not cause reduced survival or growth rate.
Interpretation of these studies is somewhat hampered by the fact that fish have been clipped at different ages under different environmental conditions, and have been collected or recaptured at different time periods after marking. In addition to these variables, one technique may be carried out differently between operators and studies. Other variables include handling stress, anaesthetic methods and the health status of the fish. Some studies evaluate the cost or durability of fin clipping, while others mainly focus on growth and/or survival effects. There are few directly comparable studies, which makes it harder to draw firm conclusions on whether fin clipping is an acceptable method or not.

Fin clipping is used extensively because it is cheap and quick compared to other methods (Hammer & Blankenship 2001, Thompson et al., 2005). Hand et al. (2010) demonstrated that fin clipping can be automated without having negative effects on fin clip quality and injury rate when performed by experienced markers. Several fins can be clipped, to provide a large number of combinations. In addition, it requires a minimum of equipment. It is thought to cause little or no suffering to the animal due to the short handling time and because few nocireceptors are located on the fins.

One of the disadvantages of this method becomes apparent when fish of a specific group are to be identified over a period of growth. For example, as the fish grows, the shape of the cut can change as the fin regenerates, making identification difficult. Another disadvantage is fish mortality: the cut can produce an open, bleeding wound which does not heal properly, making the fish susceptible to infection by bacteria, viruses and fungi.

Some studies suggest that fin clipping can reduce survival and hinder growth (Saunders & Allen, 1967; Shetter, 1967; Webber & Wahle, 1969; Coble, 1971; Nicola & Cordone, 1973; Mears & Hatch, 1976; O’Grady, 1984; Hansen, 1988). However, a substantial number of reports do no demonstrate deleterious effects on survival or growth (Armstrong, 1947; Radcliffe, 1950; Horak, 1969; Gjerde & Refstie, 1988; Conover & Sheehan, 1999; Pratt & Fox 2002; Thompson et al., 2005; Vander Haegen et al., 2005; Zymonas & McMahon 2006; Dietrich & Cunjak 2006; Zerrenner et al., 2007; Champagne et al., 2008; Bumgarner et al., 2009).

Fin clipping can potentially affect swimming performance, predator avoidance and the ability to find and capture prey. However, Wagner et al. (2009) found that fin removal (one or both pectoral and pelvic fins, all paired fins, and a non clipped control) did not compromise foraging behaviours for juvenile muskellunge (Esox masquinongy) foraging on moderately evasive prey, and that fish showed immediate behavioural compensation.
In a study by Champagne et al. (2008) on Brown Darters (Etheostoma edwini), the entire right pectoral fin or rear half of the caudal fin was removed without it affecting swimming performance in an experimental flow chamber. Horak (1969) showed that a range of fin clips (dorsal fin, both pectoral fins, both pelvic fins, anal fin and adipose fin) did not reduce the swimming ability of rainbow trout in a swim tunnel in a short term study. However, other studies have shown that various types of fin clipping affect swimming or manoeuvring ability for some species. Clipping the upper lobe of the caudal fin of bonytail chub (Gila elegans) and humpback chub (Gila cypha) decreased swimming ability in laboratory tests, and may influence the ability of fish to maneuver or maintain position in swift flowing streams (Ward, 2003). Clipping one or both pelvic fins, however, had little effect on swimming ability.
Removing the pectoral fins of pike fishes (Esocidae) is probably more harmful than removing the pelvic fins, since the pectoral fins are especially important to these species (McNiel & Crossman, 1979). These studies on swimming ability illustrates the importance of adapting the fin clipping technique to different species, since swimming ability affects both survival and growth.
Handling and severing fins is known to be stressful to fish (Sharpe et al., 1998; Barton et al., 2002) and can be a potential vector for bacterial infection (Elliot & Pascho 2001; Vander Haegen et al., 2005). Decreased survival of fish can result when physiological stress responses remain elevated and become debilitating, leaving fish vulnerable to predation or swimming challenges (Barton, 2002; Portz, 2007).
Another important issue when using fin clipping as a marking method is the regeneration time of the different fins. Several studies show that the adipose fin is most suitable for long term studies (Armstrong, 1947; Stauffer & Hansen, 1969; Weber & Wale, 1969; Johnsen & Ugedal, 1988), since it shows least regeneration, followed by the pelvic fins. Pectoral fins and the anal fin regenerate more quickly and are not suitable for studies lasting over one year. Most of the studies which reported no effects on growth and survival clipped the adipose fin and pelvic fins.
Clipping more than one fin led to reduced survival for salmonids compared to clipping only one fin (Mears & Hatch, 1976; Johnson & Ugedal, 1988). Even though the adipose fin clip has the advantage of slow regeneration and low effect on survival, it can present a problem for male spawning success (Næsje et al., 1988). The male’s adipose fin grows faster than the female’s fin prior to spawning, suggesting it plays a role in rivalry and/or pair formation. Studies that investigated return rates of salmon suggest that the pelvic fin may be a better alternative, whereas in studies where salmon are held in cages or tanks the adipose fin may be better. More research is needed to conclude with certainty which fin to clip for each species. Fin clipping methods must also be adapted to fish age, life stage and environmental conditions. In addition, protocols should be developed to minimize the induced stress on fish.
The differences in findings between studies may be due to a number of reasons, including water quality and other environmental conditions and the duration of the observation period.

Common to most studies showing negative effect on survival and/or growth is that they were performed under natural environmental conditions. Factors such as predation and competition may increase differences between marked and unmarked fish.

Armstrong GC (1947): Mortality, rate of growth, and fin regeneration of marked and

unmarked lake trout fingerlings at the Provincial Fish Hatchery, Port Arthur,

Ontario. Transactions of the American Fisheries Society 77:129–131.
Barton BA, Morgan JD & Vijayan MM (2002): Physiological and condition related indicators of environmental stress in fish. In Biological Indicators of Aquatic Ecosystem Stress, S.M. Adams (Ed.), pp. 111-148.
Bumgarner JD, Schuck ML & Blankenship HL (2009): Returns of Hatchery Steelhead with Different Fin Clips and Coded Wire Tag Lengths. North American Journal of Fisheries Management 29(4): 903-913.
Champagne CE, Austin JD, Jelks HL & Jordan F (2008): Effects of Fin Clipping on Survival and Position-Holding Behavior of Brown Darters, Etheostoma edwini. Copeia 2008(4): 916-919.
Coble DW (1971): Effects of fin clipping and other factors on survival and growth of

smallmouth bass. Transactions of the American Fisheries Society 100(3):460-473.

Conover GA & Sheehan RJ (1999): Survival, Growth, and Mark Persistence in Juvenile Black Crappies Marked with Fin Clips, Freeze Brands, or Oxytetracycline. North American Journal of Fisheries Management 19(3):824-827.
Dietrich JP & Cunjak RA (2006): Evaluation of the Impacts of Carlin Tags, Fin Clips, and Panjet Tattoos on Juvenile Atlantic Salmon. North American Journal of Fisheries Management 26(1):163-169.

Elliot DG & Pascho RJ (2001): Evidence that coded wire-tagging procedures can enhance transmission of Renibacterium salmoninarium in Chinook salmon. Journal of Aquatic Animal Health 13(3): 181-193.

Gjerde B & Refstie T(1988): The effect of fin-clipping on growth rate, survival and sexual maturity of rainbow trout. Aquaculture 73(1-4): 383-389.

Gunnes K & Refstie T (1980): Cold-branding and fin-clipping for marking of salmonids. Aquaculture 19(3): 295-299.

Hammer SA & Blankenship HL (2001): Cost Comparison of Marks, Tags, and Mark-with-Tag Combinations Used in Salmonid Research. North American Journal of Aquaculture


Hand DM, Brignon WR, Olson DE & Rivera J (2010): Comparing Two Methods Used to Mark Juvenile Chinook Salmon: Automated and Manual Marking. North American Journal of Aquaculture 72(1):10-17.
Hansen LP (1988): Effects of Carlin tagging and fin clipping on survival of Atlantic salmon (Salmo salar L.) released as smolts. Aquaculture 70(4): 391-394.

Horak DL (1969): The effect of fin removal on stamina of hatchery-reared rainbow

trout. Progressive Fish Culturist 31: 217–220.
Johnson BO & Ugedal O (1988): Effects of different kinds of fin-clipping on over-winter survival and growth of fingerling brown trout, Salmo trutta L., stocked in small streams in Norway. Aquaculture and Fisheries Management 19(3): 305-311.
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McNiel FI & Crossman EJ (1979): Fin clips in the evaluation of stocking programs for muskellunge, Esox masguinongy. Transactions of the American Fisheries Society 108: 335-343.
Mears HC & Hatch RW (1976): Overwinter survival of fingerling brook trout with single and multiple fin clips. Transactions of the American Fisheries Society 105(6): 669-674.
Nicola SJ & Cordone AJ (1973): Effects of fin removal on survival and growth of rainbow trout (Salmo gairdneri) in a natural environment. Transactions of the American Fisheries Society 102: 39-47.
Næsje TF, Hansen LP & Jarvi T (1988): Sexual dimorphism in the adipose fin of Atlantic salmon, Salmo salar L. Journal of Fish Biology 33(6): 955-956.
O’Grady MF (1984): The effects of fin-clipping, floy-tagging, and fin-damage on the

survival and growth of brown trout (Salmo trutta L.) stocked in Irish lakes. Fish

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(Oncorhynchus tshawytscha) at south Delta fish salvage operations: effects on

plasma constituents, swimming performance, and predator avoidance. Doctoral

dissertation. University of California, Davis.

Pratt TC & Fox MG (2002): Effect of Fin Clipping on Overwinter Growth and Survival of Age-0 Walleyes. North American Journal of Fisheries Management 22(4): 1290-1294.
Radcliffe RW (1950): The effect of fin-clipping on the cruising speed of goldfish and coho salmon fry. Journal of Fisheries Research Board of Canada 8: 67-73.
Saunders RL & Allen KR (1967): Effects of tagging and of fin-clipping on the survival and growth of Atlantic salmon between smolt and adult stages. Journal of Fisheries Research Board of Canada 24: 2595-2611.
Sharpe CS, Thompson DA, Blankenship HL & Schreck CB (1998): Effects of routine handling and tagging procedures on physiological stress responses in juvenile Chinook salmon. The Progressive Fish-Culturist 60(2): 81-87.
Shetter DS (1967): Effects of jaw tags and fin excision upon the growth, survival, and exploitation of hatchery rainbow trout fingerlings in Michigan. Transactions of the American Fisheries Society 96(4): 394-399.
Stauffer TM & Hansen MJ (1969): Mark retention, survival, and growth of jaw-tagged and fin-clipped rainbow trout. Transactions of the American Fisheries Society 98(2): 225-229.
Thompson JM, Hiredotha PS & Eggold BT (2005): A Comparison of Elastomer Marks and Fin Clips as Marking Techniques for Walleye. North American Journal of Fisheries Management 25(1): 308-315.
Vander Haegen GE, Blankenship HL, Hoffmann A & Thompson DA (2005): The Effects of Adipose Fin Clipping and Coded Wire Tagging on the Survival and Growth of Spring Chinook Salmon. North American Journal of Fisheries Management 25(3): 1161-1170.
Wagner CP, Einfalt LM, Scimone AB & Wahl DH (2009): Effects of Fin-Clipping on the Foraging Behavior and Growth of Age-0 Muskellunge. North American Journal of Fisheries Management 29(6): 1644-1652.
Ward DL (2003): Effects of Marking Techniques and Handling on Swimming Ability of Bonytail Chub. Journal of the Arizona-Nevada Academy of Science 36(1): 34-36.
Webber D & Wahle RJ (1969): Effect of fin-clipping on survival of sockeye salmon (Oncorhynchus nerka). Journal of Fisheries Research Board of Canada 26: 1263-1271.
Zerrenner A, Josephson DC & Krueger CC (2007): Growth, Mortality, and Mark Retention of Hatchery Brook Trout Marked with Visible Implant Tags, Jaw Tags, and Adipose Fin Clips. The Progressive Fish-Culturist 59(3): 241-245.
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