Stickleback Species Pairs
Restricted to only a few lakes, these fish have fascinated scientists around the world.
Ministry of Environment, Lands and Parks sitive to the effects of settlement and () has designated the Enos Lake industrial activities. Although the lakes stickleback species pair as Threatened are in relatively rural parts of the and will soon be determining the desig- province, they have already been affected nation for the Texada Island pairs. What are stickleback by human activities such as logging, land Stickleback species pairs present a species pairs? clearing, water removal, road building, difficult taxonomic (classification) prob- he fish known collectively as “stick- septic tank inputs and introduction of lem for biologists. They are very closely leback species pairs” are small, exotic species. The opportunity to enjoy related to, and are descended from, the freshwater fish which are of particu- and study these rare species will be lost if Threespine Stickleback, Gasterosteus T lar scientific interest because of their steps are not taken to protect their habi- aculeatus, but are clearly different evolutionary history and their extreme- tats. The sudden extinction of the Las- species. This raises the question of ly limited distribution. They are queti Island pair emphasizes the extreme whether they represent two species of descended from the ocean-dwelling susceptibility of these wonderful “made fish living in five (previously six) lakes, or Threespine Stickleback, which is in BC” fish. 12 distinct species, now reduced to 10 by common in coastal marine waters the Lasqueti extinctions. Or whether the throughout the Northern Hemisphere. What is their status? answer lies somewhere between these Populations of freshwater sticklebacks tickleback species pairs are among possibilities. More research must be are often found in low-elevation coastal the rarest and most threatened done before the stickleback species pairs lakes and streams, but it is only in a very species in the world. Unlike many can be given scientific names. Scientists few locations that marine sticklebacks Sspecies that are rare in Canada but at the University of British Columbia have evolved into species pairs – two found elsewhere, the stickleback species hope to solve this mystery by comparing distinct but closely related species living pairs exist nowhere outside this corner of the DNA (genetic material) of fish from side-by-side in the same lake. our province. One pair – the two species the different lakes. Regardless of their that formerly inhabited Hadley Lake on findings, however, the status of the stick- Why are they at risk? Lasqueti Island – is now officially extinct. leback species pairs will remain “critical- tickleback species pairs are at risk The rest of these unique sticklebacks ly imperilled.” because their natural distribution is are abundant and healthy in the five restricted to southwestern British lakes in which they are currently found, What do they look like? SColumbia, where the already but because their ticklebacks are minnow-like fish usu- large human population is grow- populations are ally not more than 70 millimetres in ing rapidly. The entire worldwide The sudden so localized, they length at maturity. Their common distribution of these fish is now remain at risk. Sname is derived from the three spines extinction of restricted to five small lakes – one They are on the that project upward from the back. Their on Vancouver Island and the oth- the Hadley provincial Red distinctive armour also includes two ers on Texada Island. A species Lake pair List of species stout pelvic spines that project sideways pair that once inhabited a sixth being considered from the belly. These sharp spines, which lake, on Lasqueti Island, went emphasizes for legal designa- can be retracted or locked open, present extinct in the mid-1990s as a the tion as Endan- an excellent defence against predators. In result of the introduction of gered or Threat- addition to spines, sticklebacks have catfish to this lake. This event susceptibility ened. The BC small plates of armour along their sides, highlighted how vulnerable these of these Conservation and the head region is protected by fish are. We have now lost forever Data Centre has external bony structures. Despite all the one-sixth of the species pairs. “made in also placed stick- armour, the fish appear quite delicate The coastal lakes that stickle- BC” fish. leback species and are not very powerful swimmers. back species pairs inhabit are like pairs in their Each stickleback species pair is made tiny islands in a sea of land and highest risk class, up of a benthic species and a limnetic salt water, all of which is uninhabitable Category 1, defined as “critically imper- species, so named because of where each for these fish. The sticklebacks are illed because of extreme rarity.” At the is found and what they tend to eat. Ben- dependent on humans not to destroy or national level, the Committee on the Sta- thic means associated with the bottom degrade these lakes, which are very sen- tus of Endangered Wildlife in Canada of the lake. Limnetic means associated with the water column above the lake limnetics. Their chunky bodies appear netics have many long gill rakers that bottom. When they are very young it almost cumbersome. Additionally, their form a fine-toothed comb that allows takes a trained eye to tell them apart, armour is sometimes reduced to the them to eat very small plankton. but by the time they reach maturity, point where they have only one or In the spring and early summer benthics and limnetics take on quite two spines, and fewer lateral plates both limnetic and benthic males shed distinctive features. than limnetics. Benthics generally their camouflage for striking mating Limnetics are delicate, slender, have a dark, mottled colouring that colours. Males develop bright red streamlined fish with light- makes them very dif- throats and brilliant blue eyes and coloured bellies and silvery In spring ficult to see against bodies. This colouring makes them sides. As adults, limnetics live in the bottom vegeta- attractive to females in much the same the offshore regions of the lake and early tion that is their way the peacock’s bright plumage where they feed on plankton. summer, favoured habitat. appeals to the peahen. After mating Their colouring allows them to Internal charac- season, males regain their camou- blend into their background males shed teristics, particularly flaged appearance. when viewed from any angle. their feeding structures Camouflage is especially impor- called gill rakers, can What makes them unique? tant for small fish living in the camouflage also be used to tell tickleback species pairs are among middle of a lake, since there is for striking benthics from lim- the youngest species on earth. Scien- no place for them to hide from netics. Gill rakers are tists believe they have evolved since predators. At maturity, limnet- mating stiff, finger-like parts Sthe end of the last glaciation, approx- ics are considerably smaller colours. of the gill that project imately 13 000 years ago. The evolution than benthics, yet have longer, into a fish’s throat, of a new species is usually thought to sturdier spines, and lateral forming a comb-like take millions of years. The speed with plates that are more heavily armoured. sieve that can trap food items. Benthics which these distinct fish species evolved Benthics are much more robust than have only a few short gill rakers. Lim- has intrigued and excited scientists from around the world. Newspapers, maga- plenty of luck, as conditions had together with glue-like secretions from zines and academic journals have pub- to be almost perfect for it to work. their kidneys. The nest is a small, lished the story of the discovery of these This may explain why species pairs roundish “blanket” placed over a shal- species, and have followed the ongoing have not been found elsewhere. low trench that the male scoops out scientific study of the stickleback One issue that has captured a great with his mouth. The blanket is well- species pairs. deal of attention is the possibility camouflaged against the surface on Typically, marine sticklebacks that the process occurred inde- which it is built, enter freshwater streams to repro- pendently in each lake, such Stickleback and is rarely larger duce. After hatching, young stickle- that each ended up with a dif- in diameter than backs return to the sea to grow and ferent species pair. In other species pairs twice the length of mature. During the last Ice Age, words, the species pair in Pax- are among the male. It has marine sticklebacks likely gained ton Lake may be different a hole in the cen- access to and bred in new streams as than the pair in Enos Lake. As the youngest tre through which the glaciers receded. Scientists believe researchers examine DNA of species on the female must that, after a while, some of the young these fish they will determine squeeze to deposit sticklebacks in each stream no longer whether the double invasion earth. her eggs. returned to the sea to complete their may have occurred at the Sticklebacks are life cycle, but instead stayed resident same time in different locations. renowned for their elaborate mating in fresh water until their death. This Biologists are also working to dances, as well as the males’ eye-catch- process appears to have been repeat- understand the current ecological ing mating colouring. When a female ed many times along the west coast of processes that allow benthics and with her abdomen swollen with eggs North America, with the result that limnetics to coexist. approaches his territory, the male freshwater populations in coastal Stickleback species pairs are a sci- darts quickly back and forth in a “zig- streams and lakes are now common. entific treasure. They are a remark- zag” dance. He then chases the female No one is certain how stickleback able research subject that will help us and nips or bites at her belly. If species pairs evolved, but scientists understand the biological and physi- sufficiently attracted to the male, she think they may be the result of a “dou- cal processes that have given us the responds with a “head up” display, by ble invasion.”The theory is that marine tremendous diversity of organisms hovering in place while pointing her sticklebacks gave rise to an initial fresh- we see around us. head upward. The male then leads the water lake population which eventual- female to the nest and shows her the ly became cut off from the sea for some How do they reproduce? opening. The female enters to deposit period of time. When shifting sea lev- n the spring, male sticklebacks her eggs, and the male quickly follows els restored access to the sea, marine change from drab, timid fish that behind her to fertilize them. sticklebacks had the chance to “invade” scurry for cover at any sudden move- Male sticklebacks try to mate with the lakes a second time. It is thought Iment, to brightly coloured suitors as many females as possible over a that barriers to movement between and highly aggressive territory period of three or four days. A large marine and freshwater environments defenders. From April to June, males limnetic female might carry 50 to 60 may have been in place long enough stake out territories in the shallows of eggs and a large benthic up to 200 that by the time marine sticklebacks the lake and begin to build nests of eggs. Some limnetic males have been invaded a second time, individuals debris, small sticks and vegetation held observed with more than 1000 eggs from the initial invasion no longer rec- ognized them as potential mates. With no interbreeding, a second distinct freshwater species could then evolve from the marine form. This theory suggests that benthics evolved during the initial invasion and that limnetics arose from the second invasion. Distribution of As straightforward as the double Stickleback Species pairs invasion process sounds, it involved in one nest. Despite the fact that rocky surface, the fish darts for- limnetics and benthics breed at ward and grabs it. Benthics eat the same time of year, they al- similar food types throughout most never interbreed. their life, gradually shifting to After the female deposits her much larger prey as they get eggs in his nest, parental care bigger themselves. becomes the responsibility of the male, who expends signifi- Where do they live? cant effort in fulfilling his tickleback species pairs are duties. He must fan the eggs currently found in Priest, with his pectoral fins for a peri- Balkwill, Paxton and Emily od of about one week. If he fails Slakes on Texada Island, and in to keep well-oxygenated water Enos Lake near Nanoose Bay on flowing over the eggs, the Vancouver Island. A now extinct embryos will die. The male species pair lived until recently in must also vigorously defend the Hadley Lake on Lasqueti Island. nest, and he does so fearlessly, Stickleback species pairs may whether the intruder is an exist elsewhere, but biologists invertebrate, another stickle- have surveyed many lakes along back or even a human. Males the coast of British Columbia, continue to protect the young Washington and Alaska for these after they hatch, sometimes for unique fish, and found them more than a week. . Todd Hatfield photo nowhere else. It is possible that species pairs used to exist in What do they eat? tors and their spines are sufficiently big other coastal lakes and went extinct imnetic and benthic sticklebacks eat to act as a deterrent. Limnetics then before biologists discovered them. quite different foods. As move as schools adults, limnetics feed primar- into the open What can we do? Lily in the surface waters away Sticklebacks water to forage he lesson in the demise of the from the lake margins. There are fascinating for plankton. Hadley Lake stickleback pair is that they hunt in loose schools for Benthics, on preservation of our native fish copepods, Daphnia (water fleas) creatures that the other hand, T fauna will come about only and insect larvae – small inverte- represent a forage along the through a combined process of public brates called zooplankton that shallow margins education, strong legislation and prop- are barely visible to the human significant of the lake for er enforcement. eye. Limnetic sticklebacks are treasure to larger prey such It is unlikely that catfish were intro- well adapted to catching these as snails, clams, duced to Hadley Lake with malicious tiny but relatively fast-moving the world’s dragonfly intent. Such introductions can have a prey. It is fascinating to watch a scientific nymphs, amphi- variety of sources, such as children limnetic stickleback as it draws pods and the capturing live animals at one site and itself into an S-shape, then strikes community. worm-like lar- letting them go at another; anglers forward, opening its mouth at vae of midges introducing small fish into lakes in the the last moment to engulf a copepod. called chironomids. These inverte- belief that they are providing better As young juveniles, limnetics feed at brates are found attached to plants, or prey for their favourite trout or will the lake edges among the reeds and sub- crawling along rocks or through the improve angling opportunities; aquar- merged plants where they can seek mud. Benthics feed by swimming ium enthusiasts dumping their stock cover if approached by a potential slowly in a start-and-stop fashion into local lakes; and mistakes being predator, such as a Cutthroat Trout. over the bottom. They move forward, made in the management of natural Toward late summer, limnetics become then pause and hover over a spot. If a resources. Legislation alone is not large and swift enough to escape preda- prey item is detected on a plant or going to prevent such mishaps, even . () () Don McPhail photo () . () Don McPhail photo . Don McPhail photo
Sticklebacks are fascinating crea- these fish and the habitats they rely on. tures in their own right and represent You can take a stewardship role in pre- a significant treasure to the world’s sci- serving and managing fish habitat. entific community. However, you And you can encourage the study of don’t have to be a scientist to enjoy native species in our public schools. As them. Even casual study of their interesting as these fish are to scien- behaviour and habits amply repays the tists, it will not be science that pre- amateur naturalist. If you are interest- serves sticklebacks for future genera- . ed in protecting stickleback species tions – it will be the diligent work of Don McPhail photo pairs or other native fish fauna, there concerned citizens acting as stewards are a variety of actions you can take. of the lakes inhabited by stickleback when coupled with proper enforce- You can start by learning more about species pairs. ment. While legislation and enforce- ment are only part of the answer, public , : education is probably the most essential Ministry of Fisheries ingredient for long-term fish and wild- PO Box 9359, Stn Prov Govt life conservation. Victoria, B.C. V8W 9M2 The question is, how can we create and foster an interest in species like , : these? Sticklebacks are not the stuff of BC Conservation Data Centre the evening news. They do not have the Ministry of Environment, Lands and Parks mythical stature of Pacific salmon, nor PO Box 9344, Stn Prov Govt are they ever likely to provide much Victoria, British Columbia V8W 9M1 economic return. But salmon have not www.elp.gov.bc.ca/wld/cdc always enjoyed the status they have today, and the shift in attitude has come about largely as a result of public educa- tion. Salmon are now held in extremely high regard and many citizens volunteer their time to restoring and protecting salmon habitat. The challenge now is to extend this educational success to other --- species in our native fauna. Public . , knowledge and awareness probably rep- resent the best hope for preserving indigenous species like the stickleback species pairs. Printed in British Columbia on recycled paper with vegetable inks Q.P 4500015472