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Home , Arctic char, Sunapee trout

The beauty tf

I"", can be described The color patterns are caused by variations as fusiform-shaped, soft-rayed with a in skin pigments. These pigments in the cells terminal mouth, which is to say that they reflect light, particularly red, yelloq orange. have a body shaped like a dart, fins with brown, and black, to produce the trout's ex- flexible spines, and a mouth in which neither ternal colors. Some ofthese cells, called chro the upper nor the lower jaw extends. But the matophores, contain more than one type of most obvious and the most pleasing feature is pigment, and some pigments can move in their coloration. the cytoplasm of the cell to produce changes The and the western in colors. The more spectacular colors, blue (cutthroat, rainbow, golden, Mexican for example, are produced in special reflecting golden, Apache, and ) have a pat- chromatophores called iridophores. Small, tern of darker spots against a lighter back- flat structures within the iridophores reflect ground. The chars (brook, bull, and these unusual colors. These chromatophores trout; and Dolly Varden char) gener- and iridophores provide the principal sources ally have a white leading edge on the anal and of color and occur at many locations in the pelvic fins and a pattern of lighter-colored skin as well as elsewhere in the body, the spots against a darker background. Beyond eyes, for example. When individual fishes un- basic spottingpatterns, various colors may be dergo color changes, there is a migration of present. For example, have spots pigment within the chromatophores to with blue aureoles; brown trout have faint create vivid concentrations of color on the halos around dark spots. . The bright red or orange on the under- There may be unique body colorations as sides ofspawning brook trout and well, such as the brown-golden color of illustrates this phenomenon. brown trout or the reddish lateral stripe of Young fish in streams, particularly in their . Or there may be unusual dor- first year or two of life, are referred to as parr, sal patterns, such as the wormlike vermicula- and the dark, oblong bars many of them tions on the brook trout. Many species can have on their sides are called parr marks. be truly described as beautiful, but the The number and shape of these marks often brightest colors are reserved for those species can be used to distinguish juveniles of inhabitingwaters at the higher elevations and many salmonid species at a life stage when in the interior regions. The golden trout of other identifying marks may not be so pro- the Sierra Nevada of California, for example, nounced. In some species, these marks re- has a vivid red to red-orange belly and oper- main through adulthood; in others they dis- cula (gill covers), golden sides, reddish appear as the fish grows and develops distinct orange lateral bands, and a dark back. species coloration.

I6 Tnour The vividly colored spotting pdtterns of trout class them among the most beautiful cf all Jreshwater fuh. The chars (brooh trout, upper left; Arctic char,lower left) have light spots on darh bachgrounds. The brown trout (upper right) dnd the western trouts

(w e stslo p e cutthro at, low er right) can be recognized by their darh spots onlighter z o bachgrounds. or z

"*-:.lromous, or sea-run, fish lose therr obstructions to its downstream passage, such ir-:: :la-rks and develop a silvery coloration as as dams. :' :" 5e11' from parr to smolt before migrat- During spawning as well, trout, particu- : : Lhe sea. Sea-run trout generally have a larly the males, often develop different, ,il-,ri jorsal surface and silvery sides while at sometimes quite brilliant, coloration. Males ri ;]- :-tJ after returning to fresh water, though of the , for example, a sub- i *: returning to fresh water for long species of landlocked Arctic char.native to ,:-.,1s of time may lose this silvery appear- but also transplanted to two in a ,,. r -: rnd develop colors similar to those of the Sawtooth Mountains of , develop ,' ^ :: reshwater residents. The silvery color- bright orange-red underside during fall , : i- provides protective countershading at spawning. Other species, such as sea-run cut- i:r, ;. phenomenon known as Thayer's throat trout, darken at the time of spawning. *--.;rrle : Avian predators see only a dark In addition to color variations caused by ii:-::e. and aquatic predators looking uP see these life changes, color patterns can difFer light pattern against the bright sky. between individuals of the same species be- basic coloration of trout generally cause of the availability and the type of food, ', .-ri-s only during two stages oflife. During especially the number of red, yellow,"and "" - carotenoids, or pigments. If trout eat " ,ipment from parr to smolt in anadro- orange '-r : trout) not only do the sides of the mysid shrimp, for example, they will develop " :', develop a silvery sheen, but also the more of a reddish coloration in the flesh, and " :.r. or top: surface usually turns dark and their external colors often may be more bril- ;r: :irr marks fade. The scales during this liant. So a in one body of ',:': ,ol are loose, and the fish can be easily water can look different from one in another ir:-::ird and can lose them if it encounters locale. For example, cutthroat from the Willamette in Oregon often are quite pale, but the same in small tribu- taries in the Cascade Mountains will have brilliant colors in high contrast. The color patterns also can be a direct result of such local environmental conditions as lighting, cover, or bottom configuration. Apparendy what happens is that the chro- The oblongbars called parr with small size, matophores in the skin are affected by hor- marbs, along identtfi juvenile ftsh, although monal and nerve changes in the fish, which some species may retdin their are triggered by external stimuli, such as parr marhs into adulthood.

;,r{-ll{r e Ttour Is L7 H changes in light, cover, or the color of the oxygen can easily diffuse across the mem- substrate. Fish can cause their pigment cells brane and enter the blood. When levels I: of to fade between areas of normal color, bring- dissolved oxygen are low, trout have the abil- ing on a mottled appearance, or they can ity to increase the number of lamellae in use cause the cells to darken, creating an appear- so they can extract the greatest amount of ance that blends well with areas of cover. oxygen from the water. Booth reported in z 9. Color change in trout often is not as radical A 1979 that rainbow trout can increase the o o as it is in other fishes. Rather, the process is number of lamellae in use by some 20 per- more a change in contrast between color pat- cent when placed in conditions with lorv terns. Nevertheless, experiments by Jenkins levels of dissolved oxygen. in1969 showed that brook and brown trout could change basic background color, and LerBnar, r,rNB brown trout could develop motrled bands in flout also have a lateral line, and only one. response to dark and light colors of the unlike some other fish species. The lateral stream bottom. line is a series of sensory pores along the In 1969 andl970, Northcote and his asso- midline of each side of the fish. The exrernal ciates, studying populations ofrainbow trout pores actually are mechanoreceptors with above and below a waterfall in British Co- which trout detect water movement, avoid lumbia, found that the trout above the falls objects in their path, and sense certain chem- The gills are one of the most had a significantly higher number of parr icals critical structures of a The in the water, including pheromones fish. marks than those finger-shaped spread of the did below the falls. The from other fish. Scales along the lateral line gill flaments crea.tes d large difference probably is related to rwo phe- are unlike scales elsewhere on the bodl'. surface area that mLximizes nomena: differences in spawning times, so They have small canals that allow water to op p or tunities Jor oxJ gen that extrctction and carbon dioxide fish were subjected to different warer flow along the sensory stmctures of the removal. GiII flaments are temperatures, and generics. Probably a lateral [ine. easily damaged. by sediments higher number of parr marks led to better and other water pollutants. survival rates of the trout above falls, Dnr,rcerB ARnoR Sediments can act lihe sand- the paper on the gill flaments, perhaps because the higher numbers of Salmonids have smooth scales called q- eroding them away. Other pol- marks made the fish less visible to birds and cloid scales, which are quite thin and are lutants can cause the fl,aments other predators. partially embedded to mold. together, which in the skin in an overlap- reduces their surface area, ping pattern. They are found only on fishes Grr,r,s d.ecre ases oxygen e xtr a ction for which speed and reduced friction are es- potential, and stresses the frsh. Trout, like most fishes, have gills to extract sential. Thin scales provide an advantage in A stressed" poorly ftsh feeds oxygen from the water and is more lihely to become and to eliminate car- regulating buoyancy because they are light, disease-strichen. bon dioxide as water is passed across a series and they do protect the skin, though they' of grll filaments. Covering the gills on each side are opercula, bony flaps that are open posteriorly, so that water passed along the gill filaments can be extruded. These coverings over the gills are supported by a series of small pocket bones called branchiostegal rays. The grlls /-';i'./i, themselves actually consist of a series of four gill arches, with grll rakers protruding an- teriorly and fine gill filaments protruding

When an anddromous trout posteriorly. changes from parr to smolt as The gill filaments are the principal compo- part of is preparation for nents of gas exchange-extracting oxTgen migration to the sea, its scdles from the water and eliminating carbon diox- temp orarily b e come lo o se and are easily dislodged, espe- ide from the trout's system. Tiny protru- cially when the fsh is handled. sions, called lamellae, extend from each fila- Toward Bony ridge Loss of scales mahes (circulus) fish ment and thus provide a large surface area in head more susceptible to disease contact with water. Thin epithelial cells and bacterial infection. Trout com- I have scales of the cycloid type. pose the outside surface of these lamellae, so

r8 Tnour ,rlr1r 'r" -::e protection from predators. The the weight of the fish in pounds or grams, ,,,,, :: : more primitive fish species often are and L is the length in inches or millimeters. r-- --r.r and thus provide more protection. Fish biologists assign an ideal condition fac- -. -i scales generally are oval, with rings tor value (K) to the species or to a population ' *c-t srmilar to those on a cross section of in a particular area. Then, by comparing the "r : ::lnk. Unlike tree rings, however, sev- Kofan individual fish to the ideal K, they can r":i,, -:;s-called circuli-may be deposited determine the health of that fish. The I( ,L 'r .,.:. Crculi essentially are growth rings. value indicates whether the fish is overweight r:r:erate latitudes, where most trout or undernourished. ,.,-i circuli will appear closer together The differences in I( values of species in- " -"iinter months when growth slows. dicate subtle differences in body shape. A ::rber of these annual clumpings of species with a higher condition factor value ;alled annuli, determine the age of can be said to be plumper than another _ species; a species with a lower value can be cold waters, only one circulus or said to be thinner. For example, the rainbow -.'.. be deposited on scales, making the trout has a higher K than does the westslope 'i:.:- ,n of annuli virtually impossible. cutthroat trout, which in turn has a higher - -:r areas where growth is slow, annuli K than does the slimmer . It ,i, - : be obvious, in which case we can should be noted, however, that body dimen- .:rculate upon the age of the fish. Nor- sions and proportions can differ because of ,'ri.i'- researchers, working with brown how much the trout eats as well; a trout can " i . :-r\-e found that, in very cold waters, gow fat. , r' :t;.\-not form at all in the first year, so A I9B9 report by Currens and colleagues of '' -:.: annulus may not apPear until the their studies ofrainbow trout in Oregon indi- '' .il : SeCold year. cated that although the morphometric di- :.:r {rowth can be distinguished from mensions of the trunk region can change - :ier growth. The more abundant Rainbow trout (top) tend to be :' -: the ocean produce faster growth, plumper than westslope cut- :: rurn causes wider spacing between throat (middle), which in turn plumper than the -, Thus, an expert can take a scale from a tend to be -.:i.d slender lahe trout (bottom). trout and estimate the number of These difertnces are reflected

-t. ::e fish spent in fresh water and in salt in the species' condttion fac- : :rd often even the number of - tors - numerical values that indicate an ideal relationship between length and weight. : -.;r hard parts of fishes, such as fin rays, - .:rbit circuli and annuli. A cross section a anal fin, --. :ar-. usually------J --from - - pectoralf or ,:: at the base, will reveal similar growth : :rough not always in an easily read oval : - - : ;ntical function ofscales is not entirely ' - ::!tood. Lost scales can be replaced with ,:,:.;:ated scales-indicated by blank areas " :-. center. However, fish that lose too ': , - .an fall victim to stress, disease, and

Borv DTMENSToNS ' : cdn describe the typical shape of any - ::ecies as a relationship between normal -.-: and weight. ThiJ relationship is '-:cd numerically by the formula for the * ''don factor: K: W/L3, in which W is

,il,-a{T -l Tnour Is T9 Donal fin

Lateral line

Ad.ipose fin

Mandible Pectoral fin Gill operculum Parr mark Pelvic (ventral) fin

The fusiJorm or dart-lihe because of the amount of food eaten, the plane wing does against the air. With such shape of a trout's body is very dimensions of the caudal, or tail, region sel- movements, aerodynamic and" presents a a fish can move up quickly to minimum of resistdnce to dom change. It is similar to certain measure- catch insects drifting in the srream. water fow. Their terminal ments of humans: No matter how fat or thin ftout maintain their position by a carefirl mouths, with upper and lower a person)s stomach, the length of the foot or balance of buoyanry, stabiliza- jaws that essentially meet, the nose remains about the same. enable them to feed. through- tion by the median fins, and adjustment of out the water column; they the angle of the pelvic fins to compensare can tahe a crayfuh of the bot- FrNs for the respiratory currents passing through tom or sip an insect of the have three unpaired, surface with equal ease. Cod, fiout median fins: the gills. in contrast, have an upper jaw dorsal, anal, and caudal. The trout use these Fins are not simply decorative appendages; that overhangs the lower, facil- fins for stabilization and thrust. The caudal they are vital body pafts. Although studies itdting their b o ttom- e ding fe fin is homocercal in shape, meaning that have not always been behavior. Largemouth bass in complete agreement, have a lower jaw thdt juts out both lobes are equal. It is essential for researchers do concur that partial or com- somewhat; they approach changes in direction and for initial forward plete loss of any fin can have a measurable their prey below. from movement. The tail may be deeply forked, as effect on trout behavior and survival. In stud- in the lake trout, or quite squarq as in the ies in California, Nicola and Cordone found brook trout. Most trout species, however, that as much as B0 percent ofa population of have a tail that is slighdy forked. rainbow trout died if they lost their pectoral Like all members ofthe f"-ily , or dorsal fins. trout possess an adipose fin. This soft, fleshy structure lacks fin rays and is found along the |ews dorsal surface, or upper back, behind the Along the jaw are the lower jaw bone, or . mandible, and the upper ja% or maxillary. In Ti'out also have two sets of paired fins. The trout, the maxillary is free, or unattached as a pectorals are located on the lower part ofeach flap, at the posterior end of the jaw. Gener- side of the fish, just behind the operculum, ally the maxillary extends to a point below or gll covering. They are important for brak- the eye. During spawning the males of most ing. The pelvic, or ventral, fins are located species of trout and char, as do male , along the ventral surface, about midway develop a hooked jaw, called a or kuipe. along the length of the body in what is called This striking, sexually dimorphic feature the abdominal position. Trout use these fins helps males as they fight with one another in for braking, too) as well as for rapid vertical for the females. In extreme movements. A slight turn of the fins acts cases, male trout are unable to completely against water current to provide lift or de- close their mouths. After spawning, how- scent) much the way adjusting the flaps on a ever, the kype slowly disappears.

20 Trout IoBNrrrvrNG TRour nen ichthyologists identify species or ,-:.pecies or determine age and other life .-..":acteristics, sometimes the best they can - :s make an educated guess. This they do r i-l on ranges of measurements of the ex- ::al characters, because environmental fac- :i such as water temperature and the avail- ,: :n' of different foods can affect the ;::ri{'ing features. The ray count of the ,- ' fin of trout in a mountain lake in Idaho, , : instance, might differ from that of a r -nber of the same species living in the r'- amette River. The study by Northcote -: : his associates of rainbow trout above and "':, -,q'a watedall in British Columbia showed .".: the trout above the falls had significantly i-.rer numbers of lateral-line scales and ificantly lower numbers ofvertebrae than :L: those of the same species in the stream ',:-,r$-. So a range of counts and factors, such -, ie number of lateral-line scales, fin rays, ;* :akers, and other meristic features, is usu- "" provided in the description of a species. The presence and location ofteeth are used r Jistinguish species and genera. For exam- :,-- $'e can tell brown trout from brook trout : rhe presence and location of vomerine ,::ih, those along the roof of the mouth. deep into the lower part of the body. Parr marhs provide Protective coloration for young ftsh lihe and type of scale often can be .rer-are well developed along the length of The number this juvenile rainbow. - - mouth in brown trout. In brook trout) used to determine trout species or sub- ---,,rugh, they are only in a small patch at the species. Salmon and trout, for example, have : irt. In addition to these visible characteris- more and tlbhdy smaller scales-more than --;i. trout and char lack lower intermuscular llO-along the lateral line than do gay'ings :' :res. In other words, no bones extend or whitefishes, which have fewer than Il0,

-\-nueTnourIs 2L although they are all members of the familr Salmonidae. A count of lateral-line seriei scales, that is, the number of vertical rou-s of scales along the side of the body above the lateral line, is also used. Brook trout typicalh have 200 to 240lateral-line series scales, rain- bow trout have 140 to 160, golden trour have about 175, and cutthroat trout har-e 150 to 180. Recent studies at the University of Rhode Island and elsewhere have shown that er-en Meristic counts scale shape may be a means of distinguishine befween populations or races of individuals. There are indications that the genetics ot local populations, which have developed Hir,ori.ully, the morphology of fishes has over thousands of years, produce unique been the primary source of information for variations in scale shape. Thus, the "shape taxonomic and evolutionary studies. Char- discrimination" can be analyzed by com- acteristic sizes, shapes, pigmentation and puter, which sometimes can identiSr the spotting patterns, fin placement and the home locale of the fish. numbers and types of rays within them, and Each scale has a dorsal and a ventral edge, a all sorts ofother external and internal features top and bottom. By measuring the length of have been examined. a fish at capture and the overall length ofthe Meristic characters are those features that scale, we can estimate the length of the fish ar can be counted and once, in evolutionary earlier ages by measuring the proportions of history corresponded to the body segmen- the length of the scale at each annulus. This tation. These characters vary within and measurement is based on the assumption among species, and are useful in describing or that scale size increases in proportion to in- identifying fishes. The problem with meristic creases in body length. However, Rosa Lee's characters as indicators of evolutionary rela- Phenomenon states that the older the tionships is that they can be influenced by is at capture, the less accurate are estimates of environmental factors. Laboratory studies its length at specific earlier ages. Thus, back have shown, for example, that temperature calculations of length can sometimes be during early development can have consider- slightly in error, because the hard parts of able influence on such characters as scale fish, such as bones and scales, do not alwal's counts and vertebra numbers. On the other grow at a constant rate. hand, Behnke and his students have tested As a rule, trout species that live in the cold- the amount of nongenetic change due to est waters live longest, but most age determi- direct environmental effects by comparing nations are only estimates. For example, the parental populations of many western trouts age of lake trout older than about eight years with their offsprings introduced into is difficult to determine from their scales, and different environments. The results, along maximum age estimates may actually be with the results of meristic counts from quite conservative. Instead, &measure of the thousands oftrout specimens collected in the otolith, a free-floating bone that is the ear of wild, convince Behnke that certain meristic the fish, or fin rays often gives a more reliable characters are stable; that is, they are largely estimate. under genetic, not environmental, influence The most reliable technique for identifying and can be used to differentiate between the age of a trout is to retrieve identifiably species and subspecies of western trouts. marked fish. Until recently, scientists, by -Pnt Tiotnr measuring scales, had estimated the maxi- mum age of sunapee trout at eight years. But similar measurements from scales of an indi-

22 Tnour Common meristic character counts

::-::rsrics, rvhen yiewed in combination, can be relied upon to distinguish one species from another Color patterns alone :,::: r :ie ntification; a trout's colors can vary with water tempenture, diet, and other environmental factors. Meristic chancter :: j-:Jges to reflect the diIl'erences r.ithil a species. Although some ofthe nnges recorded for specific chancter counts :,::r:: :hare the same combination of tnits.

Ilteml Awl Pircipol Wtebnl lirc set*s .fin m16 dorsal.f.n mys Gillmhns tegMnts t12-t70 i0-]2 I l-12 t8-22 58-61 i, about 200 8-1 I l0-12 t9-32 60-71 197-240 9-13 10-r4 L4-22 58-62 I t6-r36 ro-t2 9-Il r4-t7 56-61 about 240 9-lt i0-12 I4-19 62-67

l 150-180 8-t2 8-lr l4-28 60-64 t86-254 9-11 10-12 tt-26 57-70 r30-i64 9-l 1 l0-12 l8-20 59-62

I 160-210 l0-12 10-14 t7-21 58-61 185-205 8-10 8-10 t6-26 6).-69 r32-t56 8-u l0-12 t7-19 56-59 llt0-160 6- l/ 10-13 I6-22 60-66 tl5-177 8-12 l0-1 3 t6-22 60-66

- * ::--, rously marked have raised that throat, Oncot hynchws clnt hi stonoias, found in r': '" r:- :.-, nineteen years. Colorado, has the highest number of scales - . * - irrrn. environmental stresses and in- along the lateral line of any western trout. '": -:- .ause the fish to lose scales and The Lahontan cutthroat, O. c. l:tenshowi, :l -:".' onesr which would not accurately confined to the Lahontan Basin of Nevada rr - ::,. age of the fish. And spawning and California, has the highest number ofgill ,r :rade at the time of breeding, can rakers of any western trout. The Paiute trout, :: :jr indication of spawning history O. c. se/tniris, has meristic characters similar to ---- iso obscure circuli and annuli be- those of the Lahontan cutthroat but, in ,: -;h checks scar the scale and can dis- many cases, Iacks spots, which are typical of * :-*- 'rs scale features. So it is sometimes other cutthroat. : i . --: io age fish by examining their scales, In additionr measurements of meristic . : :: e\perts will disagree on the age of a characters, such as length ratios ofbody seg- - t :..1 . ments) numbers of principal and branched -:. of fin rays) particularly the number fin rays, and number of scales, sometimes can :- ,:t the anal fin, is commonly used to be used to distinguish resident from sea-run " ,.- ::out species. fiout have fewer than varieties of the same species, as Mccart and '-::* oi these soft rays. Lake trout have Craig were able to do for Arctic char in I - : : :en. brown trout ten to twelve. The , or between stocks of the same * -,:: oisoft ralrs of the dorsal fin also can species, as Winter and his associates were able ..-l to identify species, though this to do for steelhead trout in Oregon. -.:-; .ount is less common because it is Biologists often use total length, from '- : :ead. Lake trout have eight to ten soft snout to tip of caudal fin, or fork length, -:r\\-n trout have nine to eleven. from snout to fork of tail, if the tail is forked. --,:: useful meristic measurements in- But ichthyologists typically use standard .*: -trLrDtS of grll rakers, branchiostegal length, a measurement from the tip of the r ::-l pectoral and pelvic rays, lengths or snout to the most posterior segment of the ;-.,-. of fins, and numbers of scale rows vertebral column) at the base of the caudal ' . -rr below the lateral line. fin. Body proportions are also useful for dis- --:-:-rugh differences are often subtle be- tinguishing species. For example, the size of '' ::- :he trout subspecies and may require the eye in relation to the size of the head may -'. -:ri e\aminations) even some subsPecies separate nvo species. In trout, however, :e dstinguished by meristic or color other characteristics, such as color and fin ray .::::-rces. Three subspecies of cutthroat counts, often are more useful. r- -: lemonstrate this. The greenback cut- -lohn R. Moring

23 'i,--{-rJ -l Tnour Is