Galaxias fasciatus:
Ecology and Conservation Implications

The Galaxiidae (Order: Osmeriformes) are a family of freshwater fish generally found in the cool-watered temperate latitudes of the Southern Hemisphere (McDowall, 2000). Galaxiidae derives its name from the comparison of the galaxy with the typical profusion of shiny flecks in the colouration of its members (Alibone, David, Hitchmough, Jellyman, Ling, Ravenscroft & Waters, 2010). Within New Zealand there are two genera of galaxiid, Neochanna, containing five species of mudfish, and Galaxias which contains twenty diverse fish species (McDowall, 2000). There is a high rate of endemism within these New Zealand genera. Only two of these species are found in other Southern Hemisphere countries (G. brevipinnis and G. maculatus) (Alibone et al, 2010). The banded kokopu, G. fasciatus, is an endemic species of galaxiid fish found throughout New Zealand and its offshore islands. However, populations appear to be sparse south of East Cape on the North Island and the east coast of the South Island (Department of Conservation, 2005). Banded kokopu occur primarily in coastal streams, rivers and lakes, but can also penetrate 180 kilometres inland through waterways in lowland areas no more 550 metres above sea level (McDowall, 2000). G. fasciatus is not considered to be a threatened species because they remain relatively widespread in distribution. However, range and abundance in several areas has declined due to habitat degradation, over harvesting of whitebait juveniles, and competition from introduced species (Alibone et al, 2010).

G. fasciatus is considered to be a large galaxiid because of its stocky build and length of up to 260 millimetres. Large adults are more often around 200 millimetres (DOC, 2005). Like all galaxiids, banded kokopu lack scales. Instead they have a thick, leathery skin that is covered with mucus. Galaxiid fish tend to suffer from fungal growth when this mucus layer gets damaged, and this is often fatal (Alibone et al, 2010). Adult G. fasciatus skin pattern consists of light brown to dark olive dorsal and ventral colouration permeated with pale vertical bands. These bands tend to be profuse in small adults and concentrated towards the tail in larger adults. Ventral colouration is typically lighter than dorsal colouration and can be silver to olive (McDowall, 2000). These physical adaptations help conceal them within their habitat. Stripe pattern, gold flecks and overall colour camouflage the fish well within water. Darker dorsal colouration conceals the fish from overhead prey, while the lighter ventral colouration does the same from below (Akbaripasand, Nichol, Lokman & Closs, 2011). Small adults are often confused with young giant kokopu, G. argenteus, because of the similar pattern displayed by the species in early maturity. Giant kokopu lose their striping as they grow and also reach much larger sizes as adults. G. fasciatus is distinguished by the black blotch located behind the head, just above the base of the pectoral fin. Juveniles have a narrow tail with pronounced central notch, but this widens and becomes more uniform in shape with age. Visible lateral lines are present in fish of all age ranges. Furthermore, the origins of the dorsal and anal fins are aligned (McDowall, 2000). G. fasciatus occurs in the cool and often slightly acidic waters of vegetation covered streams, rivers and lakes with predominant rocky substrate, undercut banks and woody debris (Akbaripasand et al, 2011; Rowe & Smith, 2001). Microhabitat use appears to be partitioned by size. Shallow pools with fine substrate and fast flowing water tend to contain smaller individuals on average. Conversely, larger individuals tend to occupy deeper, slow flowing waters with coarse substrate (Akbaripasand et al, 2011). Unlike the short-jawed kokopu, G. postvectis, banded kokopu do not appear to be dependent on native vegetation cover. Populations have been recorded within Pinus radiata plantations and heavily overgrown pasture streams (McDowall, 2000; Akbaripasand et al, 2011). Banded kokopu are predatory fish, feeding extensively on terrestrial invertebrates such as beetles, spiders and weta. Aquatic invertebrates and crustaceans (Paranephrops spp.) are also consumed, but generally only dominate banded kokopu diet when terrestrial food resources are minimal (West, Jowett & Richardson, 2005). G. fasciatus uses water current electro-sensory information to locate their prey. The lateral line is used to sense changes in water pressure, helping with navigation while the sensory organs on the head locate prey. This technique is so well honed by the banded kokopu that they can sense small insects hitting the water’s surface (Barker, Montgomery & Dennis, 2002). Banded kokopu are adapted to be quite cryptic in behaviour, often lurking camouflaged around instream debris before darting off to secure prey or evade disturbance (Rowe & Smith, 2003). G. fasciatus has an average lifespan of nine years. Males reach sexual maturity at around two years old and females mature at three years old (McDowall, 2000). This species is generally amphidromous. Breeding occurs in freshwater and larvae migrate to the ocean to grow before returning to freshwater bodies. Landlocked populations are an exception to this as larval development occurs in freshwater after short migrations (Charteris, Alibone & Death, 2003). Spawning occurs in autumn and winter during king tides and floods when banded kokopu are able to access the leaf litter of the water margins (Jowett & Richardson, 1994). Thousands of eggs around two millimeters in diameter are laid by females amongst the litter. Males then fertilise the eggs with large amounts of sperm, giving the water a milky appearance. When the water retreats the eggs are left out of water for two to three weeks (Charteris et al, 2003). The next flood triggers the hatching of tiny larvae around eight millimeters long (Jowett & Richardson, 1994).. Larval migration to the ocean then ensues. After spending four to five months in the ocean, large shoals of juvenile fish (whitebait), up to fifty millimetres long swim into river and stream estuaries on the incoming tide in spring (Charteris et al, 2003). They make their way upstream using their exceptional climbing abilities to develop into adult freshwater fish (DOC, 2005). This seasonal return of juveniles to freshwater alongside the four other whitebait galaxiids (G. argenteus, G. postvectis, G. maculatus and G. brevipinnis) is the basis of an important New Zealand fishery. Maori utilized this whitebait migration as a source of food, as well as eating adults. Early Europeans also collected whitebait and the value of this fishery grew (DOC, 2005). The growth of the whitebait industry remained unchecked until the Whitebait Fishing Regulations was drafted in 1994 under the authority of the Conservation Act 1987. Presently, commercial and recreational whitebait fisheries are controlled with strict regulations regarding permitted fishing seasons, daily times, equipment type, size and set frequency. However, there is no daily catch limit (DOC, 1994). Historical and contemporary whitebait fisheries are likely to have contributed to the decline of G. fasciatus populations despite the r-selected breeding habits of the species (DOC, 2005). The largest ongoing threat to banded kokopu is habitat degradation, separation and loss. Catchment deforestation and drainage of waterways for agricultural use are the primary sources of habitat degradation. Habitat separation can be caused by diversion of waterways for agricultural use, electricity generation or infrastructure upgrade (DOC, 2005). This galaxiid is particularly sensitive to high levels of sediments ( and ammonia within waterways (Richardson, 1997), which can occur with improperly managed livestock grazing in catchments. Research has shown that high sediment levels can deter G. fasciatus juvenile from entering a water course (although strong pheromones from a large adult population upstream can override deterrence) (Barker, 2003). These agricultural impacts can be mitigated effectively with the presence of riparian vegetation cover around waterways, and strict regulations regarding agricultural techniques (DOC, 2005). Introduced pest and game fish species compete with G. fasciatus for invertebrate prey. For example, waterways with well established trout populations are unlikely to contain banded kokopu. This is because the trout is larger and more aggressive, easily dominating the use of terrestrial and aquatic food resources. However, banded kokopu maintain stronger populations in smaller streams and swamps that cannot support trout. Management of this threat includes the control of invasive fish and the separation of game fish and native fish species (DOC, 2005).

G. fasciatus is an endemic, amphidromous fish that occurs in the coastal and lowland waterways of New Zealand. They are dependent of waterways with heavy vegetation cover and low sediment levels. Juveniles return to New Zealand waterways as whitebait after a larval period at sea. Whitebait fishing, habitat degradation and competition for food from introduced fish species have caused gradual declines in range and population. Regulating agricultural activities and whitebait fisheries is integral to preventing further anthropogenic impacts in the future.

References: • Akbaripasand, A., Nichol, E.C., Lokman, P.M. & Closs, G.P. (2011). Microhabitat use of a native New Zealand galaxiid fish, Galaxias fasciatus. New Zealand Journal of Marine and Freshwater Research Volume 45(1), 135 - 144. • Allibone, R., David, B., Hitchmough, R., Jellyman, D., Ling, N., Ravenscroft, P. & Waters, J. (2010) Conservation Status of New Zealand freshwater fish, 2009. New Zealand Journal of Marine and Freshwater Research 44(4), 271 - 287. • Baker, C.F., Montgomery, J.C. & Dennis, T.E. (2002). The sensory basis of olfactory search behavior in banded kokopu (Galaxias fasciatus). Journal of Comparative Physiology A, 188(7), 553 - 560. • Barker, C.F. (2003). Effect of adult pheromones on the avoidance of suspended sediment by migratory banded kokopu juveniles. Journal of Fish Biology, 62(2), 386 - 394. • Charteris, S.C., Allibone, R.M. & Death, R.G. (2003). Spawning site selection, egg development, and larval drift of Galaxias postvectis and G. fasciatus in a New Zealand stream. New Zealand Journal of Marine and Freshwater Research, 37(3), 493 - 505. • Department of Conservation. (1994). Whitebait Fishing Regulations. Wellington, New Zealand. • Department of Conservation. (2005). New Zealand large galaxiid recovery plan, 2003–13. Shortjaw kokopu, giant kokopu, banded kokopu, and koaro (Threatened Species Recovery Plan 55). Wellington, New Zealand. • Jowett, I. G. & Richardson, J. (1994). Comparison of habitat use by fish in normal and flooded river conditions. New Zealand Journal of Marine and Freshwater Research 28(4), 409 - 416. • McDowall, R.M. (2000) The Reed field guide to New Zealand freshwater fishes. Auckland, New Zealand: Reed Publishing. • Richardson, J. 1997. Acute ammonia toxicity for eight New Zealand indigenous freshwater species. New Zealand Journal of Marine and Freshwater Research 31(2), 185-190. • Rowe, D.K. & Smith, J. (2003). Use of in stream cover types by adult banded kokopu (Galaxias fasciatus) in first order North Island, New Zealand, streams. New Zealand Journal of Marine and Freshwater Research 37(3), 541 - 552. • West, D.W., Jowett, I.G. & Richardson, J. (2005). Growth, diet, movement, and abundance of adult banded kokopu (Galaxias fasciatus) in five Coromandel, New Zealand streams. New Zealand Journal of Marine and Freshwater Research, 39(4), 915 - 929.