Gasterosteus aculeatus

Three-spined sticklebacks can live in fresh as well as salt water. Most spend the winter in coastal waters or river mouths. They migrate in the spring to inland waters where they make a nest and lay eggs. The male has to work hard. He builds the nest, defends his territory against other males, lures the females with a complicated zigzag dance, fans the eggs with oxygen-rich water using his fins and protects the eggs and later the young sticklebacks with all its might from voracious predators.

Adults occur in fresh waters, estuaries and coastal seas (Ref. 4119). Anadromous, with numerous non-anadromous populations in brackish or pure freshwater, rarely in marine waters. In the sea, confined to coastal waters. In freshwater, adults prefer to live in small stream but may occur in a variety of habitats including lakes and large rivers (Ref. 59043). Inhabit shallow vegetated areas, usually over mud or sand (Ref. 5723). Form schools. Young associated with drifting seaweed (Ref. 12114, 12115). Juveniles move to the sea (anadromous populations) or to deeper, larger water bodies (freshwater populations) in July-August, forming large feeding schools (Ref. 59043). Feed on worms, crustaceans, larvae and adult aquatic insects, drowned aerial insects, and small fishes; has also been reported to feed on their own fry and eggs (Ref. 1998). Eggs are found in nests constructed from plant material (Ref. 41678). Males build, guard and aerate the nest where the eggs are deposited (Ref. 205). Maximum length in freshwater is 8 cm while in saltwater is 11 cm (Ref. 35388). Occasionally taken commercially in Scandinavia and processed into fishmeal and oil (Ref. 28219, 28964). Commonly used as a laboratory animal (Ref. 1998). A large bibliography is available at www.geocities.com/CapeCanaveral/Hall/1345/stickbibl.html.

 A small torpedo-shaped fish with a slender tail and broad fan-like tail fin, usually 5-7 cm long but occasionally up to 10 cm in length. Two to four, usually three, sharp spines are born on its back in front of the dorsal fin. The first two spines are long and strong while the third is small. The pelvic fin is reduced to a single fin-ray and one sharp spine. The dorsal fin is longer than the anal fin. The sides bear a few bony plates, the number of plates increasing with increasing salinity. The body is greeny brown in colour, sometimes black dorsally and often bluish with silvery scales and belly in brackish waters.The three-spined stickleback breeds in early spring and summer. In the breeding season the males develop a bright orange to red colouration on the throat. The males build hollow nests from seaweeds and aquatic plants, into which they drive females to lay eggs that the males then guard until they hatch and the young leave the nest (see Wheeler, 1969; Dipper, 2001).

Hudson Bay to Chesapeake Bay

The threespine stickleback fish (Gasterosteus aculeatus) are in marine, brackish and coastal freshwater habitats of the northern hemisphere. They are found in boreal and temperate regions of the northern hemisphere and in marine waters and lowland freshwater habitats in the Atlantic and Pacific basins.

In the Atlantic Ocean, threespine sticklebacks are distributed from the Iberian Peninsula through the British Isles to Iceland and southern Greenland, and south along the east coast of North America to Chesapeake Bay. Freshwater populations are found throughout most of this range, but do not go farther south than Maine, USA. Freshwater populations are also distributed along the coast of the Mediterranean and in inland waters across Eastern Europe to the Baltic Sea.

In the Pacific Ocean, threespine sticklebacks are found from Baja California, Mexico northward along the coast of North America, across the Bering Strait, and then along the coast of mainland Asia and Japan to the southwest coast of Korea. Marine and freshwater populations are found in Japan, but the limit of marine populations in Asia is unclear. Freshwater populations are restricted to coastal areas in both Asia and North America.

Biogeographic Regions: nearctic (Native ); palearctic (Native ); atlantic ocean (Native ); pacific ocean (Native )

The range of Gasterosteus aculeatus encompasses the coastal waters of Eurasia, Iceland, eastern Asia and Northern America. In North America, this fish ranges from Alaska to Baja California on the west coast, from Baffin Island and the west side of Hudson Bay to Chesapeake Bay, Virginia, along east coast, and it occurs also in inland areas (including Lake Ontario) along both coasts. Sometimes this species occurs in the open ocean. This species has been introduced and is established in certain areas of California, Massachusetts, and the Great Lakes (Lakes Huron, Michigan, Erie and Superior) (Fuller et al. 1999; Stephenson and Momot 2000). In Eurasia it is found along North Sea coasts of Scotland and Scandinavia; coasts of Iceland and White Sea; Atlantic coasts from Ireland northward; southeastern shore of Baltic Sea and its basin (Odra and Vistula drainages); shores of Black Sea and its northern basin (from Danube to Kuban drainages). Almost absent inland in Finland, except north of 68°N. There is a hybrid zone with G. gymnurus in the English Channel, southern North Sea, Baltic Sea and their basins. It has been introduced to northern Italy.

occurs (regularly, as a native taxon) in multiple nations

Canada

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

Global Range: (>2,500,000 square km (greater than 1,000,000 square miles)) Range encompasses coastal waters of Eurasia, Iceland, Greenland, eastern Asia, and North America. In North America, this fish ranges from Alaska to Baja California on the west coast, from Baffin Island and the west side of Hudson Bay to Chesapeake Bay, Virginia, along east coast, and it occurs also in inland areas (including Lake Ontario) along both coasts. Sometimes it occurs in the open ocean. The species has been introduced and is established in certain areas of California, Massachusetts, and the Great Lakes (lakes Huron, Michigan, Erie, and Superior) (Fuller et al. 1999, Stephenson and Momot 2000). It also has been introduced in Europe, Iceland, Greenland, and the Pacific coast of Asia (Page and Burr 2011).

Circumarctic and temperate regions: Extending south to the Black Sea, southern Italy, Iberian Peninsula, North Africa; in Eastern Asia north of Japan (35°N), in North America north of 30-32°N; Greenland.

Atlantic, Baltic Sea, North Sea, Mediterranean Sea, Black Sea and adjacent watersheds: Widespread in northern Europe and North America.

Physical description varies widely with age and habitat. In general, threespine sticklebacks tend to be streamlined and less than 10 cm long (usually from 3 to 8 cm). Freshwater populations vary in body shape, depending on the habitat they occupy. Limnetic ecotypes tend to have slender bodies with narrow mouths, long snouts, and large eyes. Benthic ecotypes tend to be deep-bodied, with a wide, terminal gape.

The fish can have a robust set of spines, a pelvic girdle, and numerous lateral bony plates (up to thirty or more on each side), but the extent of these features varies by population. Dorsal and pelvic spines vary in number, placement, and length, and the spines tend to be longer in populations that co-occur with predatory fishes. The pelvic girdle consists of a bilateral structure with an anterior process that has an ascending branch on each side, a posterior process and a spine and fin ray. The abdomen is ringed in bony armor. Marine fish almost always possess a fully developed pelvic girdle and a full complement of bony lateral plates. However, many freshwater populations have reduced armor plates and pelvic girdles, and some populations have lost these features entirely.

Although body color also varies among populations, threespine sticklebacks are generally cryptic, with brown-to-green barring above and paler coloring below. As males approach reproductive condition, they become less cryptic, and their eyes become an iridescent blue. In some populations, red coloration may expand onto the flanks behind the pectoral fin.

Range length: 3 to 8 cm.

Average length: 5 cm.

Other Physical Features: ectothermic ; heterothermic ; bilateral symmetry

Sexual Dimorphism: sexes alike; sexes colored or patterned differently; male more colorful

Dorsal spines (total): 2 - 4; Dorsal soft rays (total): 10 - 14; Analspines: 1; Analsoft rays: 8 - 10; Vertebrae: 29 - 33

Length: 10 cm

Maximum size: 102 mm ---

11.0 cm TL (male/unsexed; (Ref. 35388)); max. reported age: 8 years (Ref. 72489)

Differs from other sticklebacks in having fewer dorsal spines (usually 3 vs. 4 or more).

Distinguished uniquely from its congeners in Europe by having trunk and caudal peduncle covered by a complete series of 29-35 bony scutes. Other characters important to separate this species from other species of the genus include posterior edge of scutes crenulated and scutes forming a lateral keel on caudal peduncle. Scutes may be missing on posterior part of trunk in hybrid zone with Gasterosteus gymnurus and in some isolated freshwater populations of northeastern Europe (Ref. 59043). Identified by the 3 to 4 sharp, free spines before the dorsal fin, the pelvic fin reduced to a sharp spine and a small ray, and the series of plates along the sides of the body (Ref. 27547). Gill rakers long and slender, 17 to 25 on the first arch or strictly freshwater forms, 1 or 2 more in anadromous forms; lateral line with microscopic pores (Ref. 27547). The anadromous form is fully plated, with up to 37 plates on the sides and a rather pronounced keel on each side of the caudal peduncle (Ref. 27547). Dorsal spines separated from each other and from the soft-rayed fins, each spine having a reduced membrane attached to its posterior side; anal spine free from rest of the fin; posterior margin of pectorals nearly truncate; caudal truncate to slightly indented (Ref. 27547). Freshwater forms usually mottled brown or greenish; anadromous forms silvery green to bluish black (Ref. 27547). A few isolated populations are black (Ref. 27547). Sides usually pale; belly yellow, white or silvery (Ref. 27547). Fins pale; pectoral rays often have dark dots (Ref. 27547). Breeding males (except for black forms) become brilliant bluish or green with blue or green eyes, and the forward part of the body, especially the breast region, turns bright red or orange (Ref. 27547). Caudal fin with 12 rays (Ref. 2196).

nektonic

Benthopelagic species found to depths of 27 m, inhabits vegetated areas over sand and mud bottoms.

Gasterosteus aculeatus occupy a wide range of habitats. They have been found in small, ephemeral streams in southern California and in more permanent flowing waters of variable sizes. These fish do not tolerate high-gradient streams, and they are rarely found in habitats more than a few hundred meters above sea level. In freshwater lakes, they are divided into benthic and limnetic ecotypes. Benthic environments include shallow, relatively eutrophic lakes or the littoral zone of deeper lakes. Limnetic ecotypes are typically found in the water column of deep oligotrophic lakes. Marine fish inhabit the open ocean.

Habitat Regions: temperate ; saltwater or marine ; freshwater

Aquatic Biomes: pelagic ; benthic ; lakes and ponds; rivers and streams; coastal ; brackish water

Other Habitat Features: estuarine ; intertidal or littoral

Habitat and Ecology

Systems

• Freshwater
• Marine

Habitat Type: Freshwater

Comments: In freshwater areas, this fish typically inhabits quiet weedy pools and backwaters, or occurs among emergent plants at stream edges, over bottoms of sand and mud (Lee et al. 1980, Page and Burr 2011). Marine populations apparently are pelagic, usually staying close to shore. In some lakes, two morphologically and ecologically distinct forms may occur, differing in habitat (one littoral, the other mainly limnetic). Eggs are deposited in freshwater in a nest of plant material made by the male on the bottom in shallow water.

benthopelagic; anadromous (Ref. 51243); freshwater; brackish; marine; depth range 0 - 100 m (Ref. 50550)

Depth range based on 1382 specimens in 2 taxa.
Water temperature and chemistry ranges based on 631 samples.

Environmental ranges
  Depth range (m): -9 - 323
  Temperature range (°C): -0.481 - 13.162
  Nitrate (umol/L): 1.139 - 22.184
  Salinity (PPS): 6.180 - 35.270
  Oxygen (ml/l): 0.573 - 8.164
  Phosphate (umol/l): 0.252 - 3.328
  Silicate (umol/l): 1.984 - 72.643

Graphical representation

Depth range (m): -9 - 323

Temperature range (°C): -0.481 - 13.162

Nitrate (umol/L): 1.139 - 22.184

Salinity (PPS): 6.180 - 35.270

Oxygen (ml/l): 0.573 - 8.164

Phosphate (umol/l): 0.252 - 3.328

Silicate (umol/l): 1.984 - 72.643
 
Note: this information has not been validated. Check this *note*. Your feedback is most welcome.

 Found in shallow waters amongst seaweeds, seagrasses and pondweeds in freshwater, estuaries, rock pools and saline lagoons or coastal waters.

Depth: 0 - 27m.
Recorded at 27 meters.

Habitat: benthopelagic. Inhabits vegetated areas, usually over mud or sand (Ref. 5723). In the sea, confined to coastal waters. Forms schools. Juveniles associate with drifting seaweed (Ref. 12114, 12115). Feeds on worms, crustaceans, larvae and adult aquatic insects, drowned aerial insects, and small fishes; has also been reported to feed on their own fry and eggs (Ref. 1998). Eaten by fishes, seals and sea birds (Ref. 2850). Used as a laboratory animal (Ref. 1998).

Non-Migrant: Yes. At least some populations of this species do not make significant seasonal migrations. Juvenile dispersal is not considered a migration.

Locally Migrant: Yes. At least some populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).

Locally Migrant: No. No populations of this species make annual migrations of over 200 km.

Salt water populations migrate into freshwater for spawning (Moyle 1976).

Anadromous. Fish that ascend rivers to spawn, as salmon and hilsa do. Sub-division of diadromous. Migrations should be cyclical and predictable and cover more than 100 km.

Threespine sticklebacks are generalist carnivores and prey on limnetic and littoral invertebrates. Limnetic ecotypes in lentic environments feed on zooplankton, while benthic ecotypes feed on bottom-dwelling invertebrates in the littoral zone. Common benthic prey items include crustaceans (Amphipoda) and larval insects (Chironomidae). Threespine stickleback exhibit a predation cycle that consists of search, pursuit, attack, and capture components.

Animal Foods: eggs; insects; aquatic or marine worms; aquatic crustaceans; zooplankton

Foraging Behavior: stores or caches food

Primary Diet: carnivore (Insectivore , Eats non-insect arthropods, Vermivore); planktivore

Shoaling species outside the breeding season, especially when young. Inhabits vegetated areas, usually over mud or sand (Ref. 5723). In the sea, confined to coastal waters. Forms schools. Eggs are found in nests constructed from plant material (Ref. 41678). Anadromous and nerito-pelagic (Ref. 58426). Feeds on worms, crustaceans, larvae and adult aquatic insects, drowned aerial insects, and small fishes; has also been reported to feed on their own fry and eggs (Ref. 1998). Length in freshwater is 8 cm while in saltwater is 11 cm (Ref. 35388). Preyed upon by American mergansers.

Comments: Eats various invertebrates and fish eggs and fry. Freshwater populations feed primarily on bottom organisms or organisms living on aquatic plants (limnetic form in some lakes feeds mainly on plankton). Anadromous populations feed more on free-swimming crustaceans, also bottom organisms.

Threespine sticklebacks have many predators and are thus an important source of food for many different animals. They also act as predators for benthic invertebrates, such as amphipods and insect larvae.

Commensal/Parasitic Species:

• tapeworm (Schistocephalus solidus)

Threespine sticklebacks are small, abundant, and slow swimmers, all of which combine to make them suitable prey for many different predators. However, they have evolved several predator defenses in their morphology and behavior. Anti-predator morphology includes dorsal spines, bony lateral plates, and a pelvic girdle that consists of a pair of anterior processes with ascending branches, posterior processes and pelvic spines. Behavioral responses to predation risk include schooling, remaining close to protective cover, and predator inspection. Anti-predator morphology and behaviors tend to be more well-developed in fish from environments that contain predators.

Known predators of threespine sticklebacks include fish in the families Percidae, Esocidae, and Salmonidae. Some lakes in Alaska and British Columbia have been stocked with rainbow trout (Oncorhynchus mykiss) and silver salmon (Oncorhynchus kisutch) for game, and these fish prey on sticklebacks in those lakes. Avian piscivores that prey on stickleback fish include loons (Gaviiformes), grebes (Podicipediformes), the common merganser (Mergus merganser), herons (Ardeidae), and kingfishers (Alcedinidae). Piscivorous macroinvertebrates, such as dragonfly naiads (Odonata) and beetles (Coleoptera) feed on eggs, fry and juvenile sticklebacks. Leeches (Hirudinea) prey on stickleback eggs and have also been found to consume adult sticklebacks stuck in traps.

Known Predators:

• perch, (Percidae)
• trout and salmon, (Salmonidae)
• pike, (Esocidae)
• loons, (Gaviiformes)
• grebes, (Podicipediformes)
• common merganser, (Mergus merganser)
• herons, (Ardeidae)
• kingfishers, (Alcedinidae)
• dragonflies, (Odonata)
• beetles, (Coleoptera)
• leeches, (Hirudinea)

Anti-predator Adaptations: cryptic

In Great Britain and/or Ireland:
Animal / parasite / endoparasite
Acanthocephalus clavula endoparasitises anterior intestine of Gasterosteus aculeatus

Animal / parasite / ectoparasite
Argulus foliaceus ectoparasitises scale of Gasterosteus aculeatus

Animal / parasite / ectoparasite
fluke of Dactylogyrus ectoparasitises skin of Gasterosteus aculeatus

Animal / parasite / endoparasite
metacercarium of Diplostomum endoparasitises vitreous humour of Gasterosteus aculeatus

Animal / parasite / endoparasite
metacaria (diplostomula) of Diplostomum gasterostei endoparasitises retina of Gasterosteus aculeatus
Other: major host/prey

Animal / parasite / endoparasite
Echinorhynchus clavula endoparasitises intestine of Gasterosteus aculeatus

Animal / parasite / ectoparasite
colony of Glugea anomala ectoparasitises white cysted skin of Gasterosteus aculeatus

Animal / parasite / ectoparasite
fluke of Gyrodactylus ectoparasitises skin of Gasterosteus aculeatus

Animal / parasite / ectoparasite
colony of Ichthyophthirius multifilis ectoparasitises white spotted skin of Gasterosteus aculeatus

Animal / parasite / endoparasite
Neoechinorhynchus rutili endoparasitises intestine of Gasterosteus aculeatus

Animal / parasite / ectoparasite
tapeworm of Proteocephalus filicollis ectoparasitises intestine of Gasterosteus aculeatus

Animal / parasite / ectoparasite
plerocercoid of Schistocephalus solidus ectoparasitises distended body cavity of Gasterosteus aculeatus

Animal / parasite / ectoparasite
colony of Trichodina ectoparasitises skin of Gasterosteus aculeatus
Other: minor host/prey

Gasterosteus aculeatus (Gasterosteus aculeatus 3-spined stickleback) is prey of:
Esocidae
Podocotyle staffordi
Hysterothylacium aduncum

Based on studies in:
England, River Cam (River)
Scotland (Estuarine)

This list may not be complete but is based on published studies.

Gasterosteus aculeatus (Gasterosteus aculeatus 3-spined stickleback) preys on:
plant fragments
Chironomidae
Trichoptera
Gobio gobio
Crangon crangon
Ostracoda
Balanus balanoides
Corophium volutator
Gammarus
Hydrobia ulvae

Based on studies in:
England, River Cam (River)
Scotland (Estuarine)

This list may not be complete but is based on published studies.

Note: For many non-migratory species, occurrences are roughly equivalent to populations.

Estimated Number of Occurrences: > 300

Comments: This species is represented by a very large number of occurrences (subpopulations).

>1,000,000 individuals

Comments: Total adult population size is unknown but presumably exceeds 1,000,000. This fish is common and locally abundant in many areas. However, several unique populations have declined to very low levels of abundance including G. a. williamsoni (unarmored form from southern California) and 4 species pairs in British Columbia, one of which is now extinct (Hadley Lake, Lasqueti Island, B.C.; Hatfield 2001a, Wood 2003).

Forms loose schools except when spawning (Moyle 1976).

Available density estimates include 7-28 fish/m² in suitable habitat in Wales, 24-63 fish/m² in northwestern England, 2 fish/m² in Kamchatka, Russia, and 4-21 fish/m² in British Columbia (see sources in Wootton and Smith 2000).

Feeds on copepods, euphausiids, isopods, small fishes and fish eggs

Threespine sticklebacks rely on visual cues for mating behavior. Females tend to be attracted to more reddish coloring of males during mating seasons. They also use olfactory signals to detect the presence of conspecifics, prey, and predators. Like many other fish, threespine sticklebacks use alarm cues to avoid predation and sex pheromones during breeding. Lab-raised sticklebacks have been found to rely heavily on olfactory cues of kinship, habitat and diet, and shoal size. However, the sensory organs and pathways utilized in this communication are not well understood.

Communication Channels: visual ; chemical

Other Communication Modes: pheromones

Perception Channels: visual ; tactile ; chemical

Once eggs are fertilized, they take between 5 and 10 days to hatch, depending on the temperature of the water. Upon hatching, threespine stickleback larvae are about 4 mm in length. The larvae will continue to grow by absorption of the yolk, which they will completely consume about four days after hatching. Approximately nine days after hatching, the larvae reach a length of about 8 mm and assume the shape of the adult fish. This is the juvenile stage, in which the immature young become independent of their father. Juveniles become adults when they reach sexual maturity, which is usually within 1 to 2 years of hatching.

Spawning behavior is similar for both freshwater and anadromous forms (Ref. 28966). Just before breeding, males become very territorial. The male builds a nest of plant-material glued together with spiggin, a protein produced in the kidney (Ref. 52349). Once a nest is built, the male entices the female into the nest by performing a courtship dance which is a series of zigzag movements (Ref. 1998). A receptive female follows the male who points the opening of the nest by posing above it with his head down. The female enters the nest, deposits up to a few hundred eggs, and is driven out by the male after eggs have been deposited. The male then enters the nest to fertilize the eggs. The male can choose to court another female to enter the nest and lay eggs before entering himself to fertilise the deposited eggs. Females may lay eggs in several nests over a period of several days or may be courted by the same male (Ref. 27547). The male guards and ventilates the eggs and young (Ref. 1998). During spawning season, males develop a bright orange to red belly and blue-green flank and eyes. Eggs hatch in 7-8 days. Anadromous forms usually die of exhaustion after spawning cycle. Freshwater individuals are able to complete several cycles within one year or sometimes over several years (Ref. 59043).

Lifespans of threespine sticklebacks have been recorded in a large number of studies, but the results vary. A definitive pattern for the lifespan has not been determined. Threespine sticklebacks can live to approximately five years in the laboratory. One individual reached eight years of age in captivity.

Range lifespan
Status: captivity: 8 (high) years.

Average lifespan
Status: captivity: 5 years.

Average lifespan
Status: captivity: 5 years.

Maximum longevity: 8 years (wild)

Prior to the onset of breeding, males will develop a reproductive phenotype, including blue eyes, red throats, and red fore-bellies. During the breeding season, a male will leave the shoal and settle on the bottom in shallow water, where he will construct a nest and establish a territory. The males are are generally not monogamous, and a male often tries to lead numerous females into his nest to lay eggs. Afterward, he will fertilize all the eggs at once.

Males attract females with zig-zag-like courtship dances, and females respond with a form of dancing, as well as a "head-up" posture. The male will then lead the female to his nest, lying on the substrate next to the entrance to signify that she may enter and lay her eggs. Females lay their eggs in the male’s nest and then leave the male alone to attend to the eggs until they hatch. Once eggs are fertilized, they may take five to ten days to hatch, depending on the temperature of the water. The male nesting cycle consists of a sexual phase for 1 to 4 days, and then a parental phase after the eggs are fertilized.

Mating System: polygynous

Threespine sticklebacks breed in sloughs, ponds, rivers, lakes, drainage canals, marshes, tidal creeks and sublittoral zones of the sea. Individuals reach sexual maturity at between 1 and 2 years of age, and breeding occurs annually from late April to July.

Breeding interval: Threespine stickleback generally breed once yearly

Breeding season: late April to July

Range gestation period: 5 to 10 days.

Average time to independence: 2 weeks.

Range age at sexual or reproductive maturity (female): 1 to 2 years.

Range age at sexual or reproductive maturity (male): 1 to 2 years.

Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; fertilization (External ); oviparous

Once males shift to their parental phase, they provide all the care for their young. This includes fanning eggs with their pectoral fins to provide oxygen for the developing embryos and protecting them from predators. They also convert the nest into a nest pit, which consists of tangled vegetation where newly hatched fry can hide and rest. The males typically defend the fry up to two weeks after hatching. Paternal care has been identified as an important social factor in threespine stickleback development and learning. Sticklebacks with no paternal contact tend to fail avoiding predators later in life. These anti-predator behaviors may be stimulated at an early age as stickleback fathers chase and catch their fry when they first emerge from the nest.

Parental Investment: male parental care ; pre-hatching/birth (Provisioning: Male, Protecting: Male); pre-weaning/fledging (Provisioning: Male, Protecting: Male); pre-independence (Provisioning: Male, Protecting: Male)

Spawns in spring and summer. In most populations, most adults are 1-2 years old, do not live beyond 4 years, and presumably die at the end of their first breeding season. Reimchen (1992) described a population in Drizzle Lake, Queen Charlotte Islands, British Columbia, in which individuals lived up to 8 years. Male guards eggs and fry. Eggs hatch in about a week. Nest may contain eggs of several females.

The unarmored threespine stickleback, Gasterosteus aculeatus williamsoni, a subspecies found in California, are listed as endangered in the United States.

US Federal List: endangered; no special status

CITES: no special status

State of Michigan List: no special status

IUCN Red List of Threatened Species: least concern

Year Assessed

Assessor/s

Reviewer/s

Contributor/s

Justification

History

• 2010
  Least Concern
• 2008
  Least Concern
• 2007
  Least Concern
  (IUCN 2008)

Canada

Rounded National Status Rank: N5 - Secure

United States

Rounded National Status Rank: N5 - Secure

Rounded Global Status Rank: G5 - Secure

Reasons: Widespread, abundant, secure.

Population

Population Trend

Global Short Term Trend: Relatively stable (=10% change)

Comments: Overall, extent of occurrence, area of occupancy, number of subpopulations, and population size probably are relatively stable or declining at a rate of less than 10% over 10 years or three generations.

Major Threats

Degree of Threat: Low

Comments: On a range-wide scale, no major threats are known.

Locally, threats include human impacts on spawning habitat and water quality, stocking or other introduction of non-native, predatory fishes, including introductions of certain forms of G. aculeatus itself.

Craig (1984) noted that large-scale industrial and petroleum extraction development in the Beaufort Sea could cause direct mortality as a result of intake of juvenile fishes with seawater and indirectly harm populations by altering coastal habitat, including water circulation patterns.

The California Department of Fish and Game (CDFG) recognized that increasing development along and recreational uses of the Santa Clara River were threats to the existence of the endangered G. a. williamsoni population (CDFG 1974).

In British Columbia, beaver activity has resulted in fluctuating water levels that have reduced access to some spawning sites used by the giant stickleback (currently recognized as G. aculeatus, but considered by some scientists to be a separate species, this fish is black in color and more than twice as long as threespine stickleback; occurs only in Mayer Lake, Queen Charlotte Islands; see sources in Rubidge 2000, Species at Risk Canada 2004). Increasing human recreational use of lake habitat also threatens this population (Species at Risk Canada 2004).

In Alaska and elsewhere, non-native species such as the northern pike (Esox lucius) and stocked salmonids may threaten sticklebacks through predation and competition for juvenile food resources (Hatfield 2001a, Hatfield and Ptolemy 2001, Foster et al. 2003, Wood 2003).

Hybridization between different forms of G. aculeatus threatens the unique genetic characteristics of specific populations recognized as rare or divergent; extensive hybridization between the native G. a. williamsoni (unarmored) and introduced G. a. microcephalus (armored) forms in California contributed to declines in the now endangered G. a. williamsoni (CDFG 1974, Moyle 1976b, Fuller 2005).

Least Concern (LC)

Conservation Actions

Biological Research Needs: Studies of systematics and clarification of taxonomyshould be continued; identification of distribution and characteristics of rare/unique populations will contribute to this work. Threats posed by habitat degradation and introduction of non-native species, especially to unique populations, should be investigated.

Threespine sticklebacks have been widely studied in terms of speciation and evolutionary history because of their phylogeny and adaptive radiations. Their abundance and the relative ease to cross, raise, and maintain in the lab make them an excellent animal model for a variety of studies. Threespine sticklebacks have also served as subjects in research on environmental effects since they are considered bioindicators.

Positive Impacts: research and education

fisheries: minor commercial; aquarium: public aquariums; price category: unknown; price reliability:

Comments: Has been used in carcinogenesis testing (Metcalfe 1989).