Ameiurus melas
(black bullhead)

Pictures

Picture	Title	Caption	Copyright
Title Adult Caption Ameiurus melas (black bullhead); artwork of adult fish. Copyright Released into the Public Domain by the U.S. Fish & Wildlife Service/National Digital Library - Original artwork by Duane Raver Jr.	Adult	Ameiurus melas (black bullhead); artwork of adult fish.	Released into the Public Domain by the U.S. Fish & Wildlife Service/National Digital Library - Original artwork by Duane Raver Jr.

Identity

Preferred Scientific Name

• Ameiurus melas (Rafinesque, 1820)

Preferred Common Name

• black bullhead

Other Scientific Names

• Ameirus melas Rafinesque, 1820
• Ameiurus melas melas (Rafinesque, 1820)
• Ameiurus vulgaris Thompson, 1842
• Ictalurus melas Rafinesque, 1820
• Ictalurus melas melas Rafinesque, 1820
• Silurus melas Rafinesque, 1820

International Common Names

• English: black catfish; bullhead; catfish; catfish, black; homedpout; hornedpout; poisson-chat; yellow belly bullhead
• Spanish: bagre; bagre torito negro
• French: barbotte noire; poisson-chat

Local Common Names

• Albania: peshku mace e zezë
• Austria: schwarzer zwergwels
• Canada/Quebec: barbotte noire
• Denmark: sort dværgmall
• Finland: mustapiikkimonni
• Germany: schwarzer katzenwels; Schwarzer zwergels; Schwarzer Zwergwels
• Italy: pesce gatto
• Netherlands: zwarte Amerikaanse dwergmeerval; zwarte Amerikaanse dwergmeerval
• Poland: sumik czarny
• Portugal: peixe-gato
• Sweden: svart dvärgmal

Summary of Invasiveness

A. melas, commonly known as the black bullhead, is a species of bullhead catfish native to Canada, USA and Mexico. It has been introduced into numerous countries in Europe, South America and many states in the USA and is now established in at least 15 countries (Nijssen and De Groot, 1974; Wheeler, 1978; Copp et al., 2005; Cvijanovic et al., 2005; Musil et al., 2008; Nowak et al., 2010). This species is normally considered a detritivore but recent studies suggest its diet could include fish and fish eggs (Boet, 1980). Therefore, this species might be reducing the amount of available prey for native predators. Black bullhead may also have an indirect effect by increasing turbidity (Braig and Johnson, 2003), potentially modifying the feeding efficiency of visual predators (Reid et al., 1999; Utne-Palm, 2002). Black bullheads tend to be found in high local abundance, their behaviour could therefore interfere with accompanying species and negatively affect the behaviour of native predators and prey. A. melas is listed as a species of Least Concern on the IUCN Red List of Threatened Species (IUCN, 2015). 

Taxonomic Tree

• Domain: Eukaryota
•     Kingdom: Metazoa
•         Phylum: Chordata
•             Subphylum: Vertebrata
•                 Class: Actinopterygii
•                     Order: Siluriformes
•                         Family: Ictaluridae
•                             Genus: Ameiurus
•                                 Species: Ameiurus melas

Description

It is difficult to distinguish between sexes although the female is noticeably fuller in the breeding season. Head is large and rounded above, with small eyes. Barbels at corners of mouth are about twice as long as those near nostrils. Chin barbels are dark or black. Mouth is terminal and jaws are equal in length, or with the lower one longer; distance between isthmus and lower jaw notches almost equal to distance from lower jaw notch to tip of lower jaw. Area between head and origin of dorsal compressible, no bony ridge.

Dorsal Fins: Adipose fin short, fleshy, free at posterior end, obviously well separated from the caudal fin dorsal inter-ray membranes usually noticeably darkened.

Caudal fin: round, square, or slightly indented, never deeply forked.

Anal fin does not reach anterior rays of caudal fin; anal fin rays 17 to 24.

Tail squarish, not deeply forked. Barbs on trailing edge of pectoral spines weak or absent, especially near tip; if present near base, barbs usually catch fingernail only when moved toward base.

Coloration: variable, dorsal surface greenish, yellowish, brownish or slate grey-olive, sides lighter, ventral body bright yellow, yellow or milk-white. Fins normally conspicuously darker than the adjacent parts of the body. Anal base pale, distal two-thirds between the rays black; in young fish less than 10 cm in length, the entire fins may be black.

A. melas usually weigh less than 400 g, occasionally approaching 1 kg (2.2 pounds). It is common for them to reach lengths of 254-318 mm (10-12 inches) although specimens as big as 457 mm (18 inches) have been reported. A. melas can live for 4-5 years, although not many live beyond 3 years.

Distribution

Native to Canada, USA and Mexico, black bullhead have been introduced to Europe, South America and many states in the USA and the species is now established in at least 15 countries (Nijssen and De Groot, 1974; Wheeler, 1978; Copp et al., 2005; Cvijanovic et al., 2005; Musil et al., 2008; Nowak et al., 2010).

Distribution Table

The distribution in this summary table is based on all the information available. When several references are cited, they may give conflicting information on the status. Further details may be available for individual references in the Distribution Table Details section which can be selected by going to Generate Report.

History of Introduction and Spread

Introductions of black bullhead have historically been for either aquaculture, recreational fishing or as an ornamental species. This species was first recorded in the UK in 1885, although no location details are held. Black bullhead was introduced into France from North America in 1871 and is now widespread in Europe (Wheeler, 1978). In Poland, it is suggested that the black bullhead was co-introduced into Polish waters with the brown bullhead (Ameiurus nebulosus), at the end of the nineteenth century. In European waters, the dispersal mechanism is not clear but spread could be as a result of accidental and illegal introductions or natural dispersion between countries via watercourses (Nowak et al., 2010; Copp et al., unpublished).

Introductions

Risk of Introduction

In European waters, the dispersal mechanism is not clear and could be as a result of accidental and illegal introductions or natural dispersion between countries via watercourses (Copp et al., unpublished); however, in Poland it is presumed that their spread is a result of unregistered, illegal introduction by recreational fishers (Nowak et al., 2010). It has also been suggested that A. melas has been introduced as both an ornamental species and possibly as escapees from aquaculture. Legislature in France has identified this species as a ‘species liable to cause biological disequilibrium’ (Cucherousset et al., 2007) and as such strict rules prohibit its introduction.

Habitat List

Biology and Ecology

Genetics

The modal number of chromosomes in the black bullhead is 60 (Clark and Mathis, 1982).

Reproductive Biology

In its native range in North America, the spawning season for the black bullhead starts in late April and goes through to early June, when water temperatures are about 20-21°C (Scott and Crossman, 1973). The females scoop out a small hole or depression in the lake floor usually in water about 0.6-1.2 m (2-4 ft.) deep in soft substrate, like silt or mud (Wallace, 1967). Females produce between 2000 and 3800 eggs (Etnier and Starnes, 1993). Spawning occurs five times over a one-hour period. The males fertilize the eggs and then watch over the nest for up to ten days. When the eggs hatch, both parents will watch over the fry (Scott and Crossman, 1973).

Longevity

A. melas live for 4-5 years, although not many live beyond 3 years.The maximum reported age for black bullhead is 10 years (Froese and Pauly, 2015).

Climate

Water Tolerances

Natural enemies

Notes on Natural Enemies

A. melas have large sharp spines on both their dorsal and pectoral fins; when attacked they straighten them making them difficult to swallow and as such very few predators are able to consume them (Becker, 1983). This species also produces a mild poison that runs down the spines and into the wound. These spines combined with the species' nocturnal feeding regime make black bullheads an uncommon prey item for other fish species. Smallmouth bass (Micropterus dolomieu), largemouth bass (Micropterus salmoides), herons as well as some turtle species occasionally consume the young and small adults (Becker, 1983), with their main predator being humans.

Means of Movement and Dispersal

In European waters, the dispersal mechanism is not clear and could be as a result of accidental and illegal introductions or natural dispersion between countries via watercourses (Copp et al., unpublished). 

Pathway Causes

Pathway Vectors

Impact Summary

Economic Impact

There is potential that this species can have a negative economic impact on communities as this fish can be a 'nuisance' species taking lines/bait intended for other species. Anglers not targeting this species might therefore move on to black bullhead free waters taking not only the money from recreational fishing but tourism (food, accommodation and transportation) all of which may provide economic opportunities locally.

Environmental Impact

Impact on Habitats

Of the countries where it has been introduced in Europe there may be impacts on habitat (direct or indirect), potentially through increased turbidity related to reduced macrophyte growth and reduced stability of substrates.

Impact on Biodiversity

Impacts such as competition (for food and/or space) with native species, and predation of native species have been reported. This species is normally considered a detritivore but recent studies suggest its diet could include fish and fish eggs (Boet, 1980). Therefore, this species might be reducing the amount of available prey for native predators. Due to the generalist and opportunistic feeding habits of this species, Leunda et al. (2008) analyzed data from Spain and Portugal indicating impacts on a wide range of potential prey species as well as impacts through competition. In this study, black bullheads consumed plant material, terrestrial prey and co-occurring fish species (native or exotic), taking the most abundant and available prey. According to Marsh and Douglas (1997), introduced A. melas feed on endangered humpback chub, Gila cypha, in the Little Colorado River (USA) and may exert a negative impact on the population there. Minckley (1973) reported that A. melas is considered a pest in Arizona as it forms large populations which compete with more desirable fishes for space and food. They are also voracious predators of newly hatched gamefish (Whitmore, 1997). According to Rosen et al. (1995), introduced predatory fishes, including A. melas, are probably partially responsible for the decline of the Chiricahua leopard frog (Rana chiricahuensis) in south-eastern Arizona. 

Black bullhead may also have an indirect effect by increasing turbidity (Braig and Johnson, 2003), potentially modifying the feeding efficiency of visual predators (Reid et al., 1999; Utne-Palm, 2002). Black bullheads tend to be found in high local abundance, their behaviour could therefore interfere with accompanying species and negatively affect the behavior of native predators and prey. 

Threatened Species

Social Impact

There is potential for the black bullhead to cause a negative social impact as it can be a 'nuisance' species taking lines/bait intended for other species, because of this anglers not targeting this species might move on to black bullhead free waters. 

Risk and Impact Factors

• Invasive in its native range
• Proved invasive outside its native range
• Has a broad native range
• Abundant in its native range
• Highly adaptable to different environments
• Is a habitat generalist
• Tolerant of shade
• Capable of securing and ingesting a wide range of food
• Has high reproductive potential
• Gregarious

• Conflict
• Damaged ecosystem services
• Ecosystem change/ habitat alteration
• Modification of natural benthic communities
• Modification of nutrient regime
• Negatively impacts aquaculture/fisheries
• Reduced native biodiversity
• Threat to/ loss of endangered species
• Threat to/ loss of native species

• Predation

• Highly likely to be transported internationally accidentally
• Highly likely to be transported internationally deliberately
• Highly likely to be transported internationally illegally
• Difficult/costly to control

Uses List

Human food and beverage

• Cured meat
• Fresh meat
• Frozen meat
• Live product for human consumption

Similarities to Other Species/Conditions

A close congener to the black bullhead is the brown bullhead Ameiurus nebulosus (Lesueur, 1819). One of the main distinguishing features separating the two species is that the black bullhead is with rough or irregular small barbs on the trailing edge of the pectoral spines weak; whereas for the brown bullhead, the pectoral spike edge is with regular saw-like barbs. Other distinguishing features include the number of anal ray fins; the black bullhead has 15-21 anal ray fins, the brown bullhead 21-24. The colour pattern also varies with black bullhead being mainly solid and dark, with a white or yellow belly; faint pale yellow vertical bar at base of tail while the brown bullhead is usually mottled, but may be solid, generally yellow brown or grayish, belly usually cream or tan; no bar at base of tail.

Prevention and Control

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Links to Websites

Contributors

25/05/15 Updated by: 

Michael Godard, Consultant, Cambridge, Ontario, Canada 

26/04/04 Original text by:

Uma Sabapathy Allen, Human Sciences, CAB International, Wallingford, Oxon, OX10 8DE, UK

Distribution Maps