Gonçlves et l. Yer-round Sienti prodution griol of pn-sized slmon Growth nd osmoregultion in Slmo slr L. juveniles 1 +, 1 1/2 + nd 2 + rered under restrined slinity José Fernndo Mglhães Gonçlves 1,2, Stel Crrç 1, lfredo Dmseno-Oliveir 2, Córli Viente 1, Pulo Mrtins d Cost 1,2, Mnuel Lopes-Lim 1, Rodrigo Otávio de lmeid Ozório 2 * 1 Universidde do Porto/ICS Instituto de Ciênis iomédis de el Slzr, Lg. Prof. el Slzr 2 4099-003 Porto Portugl. 2 Universidde do Porto/CIMR/CIIMR Centro Interdisiplinr de Investigção Mrinh e mientl, R. dos rgs 289 4050-3 Porto Portugl. *Corresponding uthor <rodrigo.ozorio@iimr.up.pt> Edited y: Conept Mrgret MMnus Pimentel Reeived Jnury 18, 20 epted July 26, 20 STRCT: The freshwter phse of tlnti slmon Slmo slr L vry etween one nd eight yers. The redution of the freshwter phse is desirle to redue freshwter usge, humn resoures nd to inrese yer round vilility of pn-sized slmon. Three trils were onduted to investigte the possiility of supply the mrket in yer-round sis, with pn-sized tlnti slmon Slmo slr L. (250 300 g) in Portugl (southern limit of the nturl distriution of this speies). This study primrily imed to ompre the osmoregultory ility nd growth of different fish sizes, smolts 1+ (tril 1), 1.5+ (tril 2) nd 2+ (tril 3), in freshwter nd sewter onditions. dditionlly, effets of photoperiod were determined in smolts 1.5+ (tril 2) for oth freshwter nd sewter groups. The inrements in the plsm osmollity nd hlorine onentrtions fter sewter trnsfer suggest n identil development in the hypo-osmoregultion pity mong the different ge lsses. In ll trils, weight gin ws smller fter 30 d of sltwter trnsfer when ompred to fish rered in freshwter. However, the growth depression ws temporry. Sewter group showed ompenstory growth in the immedite months, whih permitted n improvement in growth rtes. t the end of trils there were minor differenes on growth performne etween freshwter nd sewter groups. Speifi growth rtes vried etween 0.7 nd 1.0 % dy 1, ording to the ge nd /or size nd trnsfer seson. Keywords: tlnti slmon, post-smolts development, smoltifition, sewter trnsfer Introdution The worldwide prodution of frmed tlnti slmon Slmo slr L. hs inresed stedily over the pst two dedes. This expnsion in output pity hs resulted in gret opportunity for produers to quire new innovtions nd modify tehnologies with the im of enhning their produtivity nd reduing osts, while mintining produt sfety nd qulity. Prtiulr ttention hs een given to the possiility of reduing the period of the freshwter phse y using out-ofseson smolts, to redue wter, equipment nd humn resoures onsumption nd to inrese yer round vilility (Fitzgerld et l., 2002). In ddition, for ovious eonomi resons, mngement opertions hve striven for minimum mortlity nd rpid inrese in growth rte when smolts re trnsferred to sewter (Sturnes et l., 2001). Fish growth usully inreses proportionlly to the inrese of wter temperture (rett, 1979; ustreng et l., 1987), until n optimum growth performne is rehed. Moreover, wter temperture hs strong influene on limtion to sewter nd in susequent fish performne (Solkken et l., 1994; Stefnsson et l., 1998; Hndelnd et l., 2008). Portugl represents the southern limit of tlnti slmon distriution in Europe, presenting high oeni wter tempertures (ove 18 C) t the wrmest sesons of the yer, whih severely hllenges the osmoionoregultory mehnisms nd growth performne of slmonids (Gonçlves et l., 2006). Mortlity hs een seen to inrese in these environmentl onditions nd frming results re negtively ffeted, oth iologilly nd eonomilly. s onsequene, new (nd different from trditionl) prodution system must e estlished in order to operte ommerilly in this geogrphil re. The hoie ws to derese slinity, n effetive proess to mintin the osmo-ionoregultory homeostsis in fish during long periods t dverse temperture (Hndelnd et l., 1998; Myoung et l., 1999; Gonçlves et l., 2006). This study imed to evlute the growth nd hypoosmoregultory ility of tlnti slmon Slmo slr L. smolts fter eing trnsferred to sewter (28 g L 1 ) t different times. In ddition, the results were ompred to dt otined from ontrol groups held in freshwter to investigte the possiility of supplying the mrket in yer-round sis, with pn-sized slmon (250 300 g). The trils were omplemented with nlyses of morphophysiologil prmeters tht hve een used in previous studies, either on the prr-smolt trnsformtion or in the susequent periods fter sewter trnsition. These prmeters re inditors of the viility of different types of smolts herein studied nd, therefore, of the pity of ssuring ontinuous prodution. Mterils nd Methods Rering onditions Three suessive trils were rried out using tlnti slmon silings, Mowi strin. In the first tril, smolts with ge 1 + were used, followed y seond tril Si. gri. v.70, n.1, p.-20, Jnury/Ferury 2013
13 Gonçlves et l. Yer-round prodution of pn-sized slmon with out-of-seson smolts (ge 1.5 + ) nd, finlly, third tril with smolts 2 +. In ll trils we used fish kept ontinuously in freshwter s ontrol groups. Smolts were otined from the sme stok of eyed eggs, from ommeril ulture in ommon environment under onditions stndrdized for this speies. Smolt sttus were evluted y sewter hllenge tests nd fish used in the trils presented t lest 90 % survivl during 96 h (Sunders et l., 1985). prt from the prodution of outof-seson smolts (pre-stge of tril 2), when light ws mnipulted, nturl photoperiod nd temperture were used in ll the trils (Figure 1). The trils were rried out in ommeril fish frm on the western ost of Portugl (41 25 0 N, 8 46 0 W). Temperture (ºC) Temperture (ºC) Temperture (ºC) 20 18 20 18 20 18 C Fresh wter Se wter Light 0 30 31 60 61 90 91 0 Period in dys Fresh wter Se wter Light 0 30 31 60 61 90 Period in dys Fresh wter Se wter Light 0 30 31 60 61 90 91 0 Period in dys Figure 1 Men light exposure nd wter temperture regimes in the rering of tlnti slmon Slmo slr under fresh nd sewter onditions. Vlues re given s mens ± SE. Tril 1 = Figure 1, tril 2 = Figure 1, tril 3 = Figure 1C. 15 13 11 9 8 15 13 Light exposure (hours) Light exposure (hours) Light exposure (hours) Trils were onduted in open iruit (wter flow of 0.5 L s 1 ) nd fish were fed ommeril diets (4-6mm size; 42-44 % rude protein; - % rude ft; 18-20 MJ kg 1 gross energy, in quntities reommended y the mnufturer y utomti feeders. Good qulity sewter nd freshwter entered the fish frm, s nutrient nd solids onentrtions were within the vlues oserved for unpolluted wters (nitrte levels: summer mxim of 0.54 ± 0.01 mg L 1, ph vried etween 7.8 nd 8.1, oxygen levels vried etween 9.4 nd 13.1 mg L 1 ). For eh tril, rndomly olleted su-popultion of out hlf of the fish in eh tnk ws individully tgged with visile implnts (Northwest Mrine Tehnology) for the lultion of growth performnes. This study hs een onduted in ordne with the Portuguese lws nd regultions ontrolling experimentl nimls. Tril 1 (smolts 1 + ) In My, 600 smolts 1 + (70 to 115 g) were rndomly seleted, prtilly mrked nd eqully distriuted y four tnks (4 m 3 ) in two experimentl groups (two replites per group). During the following 0 d one of the groups ws sujeted to growth tril in sewter t 28 g L 1 (smple weigh = 89.5 ± 1.0 g), while the other group remined in freshwter (smple weigh = 83.1 ± 0.8 g). The trnsfer from freshwter to the different qulities of sewter ws otined in 48 h y hnging the wter supply into the tnks, whih produed stle experimentl onditions within 1 h with n inrese rte in slinity of pproximtely 0.5-0.6 g L 1. Tril 2 (smolts 1.5 + ) This tril hd totl durtion of 90 d. It ws preeded y preliminry stge of mnipultion with totl of 0 d required to produe out-of-seson smolts. In Sep., 800 smolts 1.5 + were divided rndomly into four tnks with 4 m 3, eh. ll tnks were isolted with light proof plsti over nd light ws provided y fluoresent dylight tue mounted under eh tnk over (200 lux in the ottom of the tnks). During the preliminry stge, two tnks (su smple weigh = 83.9 ± 0.7 g; n = 50) were sumitted to nturl photoperiod regime (42 N) nd were designted s groups LN (n = 193) nd LN (n = 192). The other two tnks (su smple weigh = 75.7 ± 0.9 g; n = 50) were sumitted to ompressed winter/spring photoperiod nd were designted s groups LD (n = 191) nd LD (n = 193), eginning with 8 h of light nd sixteen of drkness during 60 d (L8:D), followed y reversion of photoperiod of h of light nd 8 h of drkness (L:D8) for the remining 60 d. In Jn., 0 dys fter photoperiod mnipultion, growth ws evluted nd hlf of the fish of eh test were tgged nd redistriuted rndomly in four 4 m 3 tnks, two with freshwter nd two with sewter t 28 g L 1. Fish in the upper nd lower limits of the weight distriution were removed in order to eliminte the differenes etween tnks in the men weight of fish. The Si. gri. v.70, n.1, p.-20, Jnury/Ferury 2013
Gonçlves et l. Yer-round prodution of pn-sized slmon fish group exposed to ompressed winter/spring photoperiod ws then sumitted to grdul inrese in slinity through 48 h (trnsition t pproximtely 0.5-0.6 g L 1 per hour) until finl slinity of 28 g L 1, in order to strt the tril 2. Tril 3 (smolts 2 + ) In My, 600 smolts 2 + (90 to 0 g) were rndomly seleted, prtilly mrked nd eqully distriuted in two experimentl groups (132.4 ± 1.7 g for freshwter nd 9.2 ± 1.2 g for sewter) ording to the sme proedures s in tril 1. Smpling proedure nd sttistil nlysis The ondition ftor (CF) ws lulted s 0 W / L 3, where W is the weight of eh fish (30 fish tnk 1, g) nd L is the orresponding fork length (m). The speifi growth rte (SGR; % W t dy 1 ) ws lulted s [(ln W 2 - ln W 1 ) / Δt] 0, where W1 nd W2 re the initil nd finl weights etween smpling nd Δt is the tril durtion (dys) etween smplings. t the end of the trils, ll the tgged fish were identified nd inluded in the finl smpling. lood smples were rndomly olleted from 8 to seleted fish for eh group t monthly intervls. ll fish were strved 24 h prior to smpling nd were lightly nesthetised fter pture with ethylene-glyolmonophenil-ether, 0.4 ml L 1. lood ws olleted y udl punture with lithium-heprin oted syringes. Plsm ws immeditely seprted y entrifugtion nd stored t -80 ºC until susequent nlysis. Plsm osmoti pressure (mosm kg 1 ) ws determined with n osmometer nd plsm hloride onentrtion (mmol L 1 ) ws ssyed with hloride titrtor. In tril 2, smoltifition ws monitored in the most importnt phses of the photoperiod mnipultion, y the mesurement of gill N +, K + -TPse tivity. Gill filments were isolted from rnhil rhes nd wshed in surose (0.25 M, ph 7.4) to remove the exess of lood, weighted nd quikly frozen in liquid nitrogen nd mintined t -80 ºC until further nlysis ording to the method of Lsserre et l. (1978). Vlues in figures nd tles re mens ± S.E. Differenes were signifint if p < 0.05. One-wy nlysis of vrine (NOV) ws performed, followed y Sheffé s multiple omprison test where ssumptions of normlity nd homogeneity were stisfied (Zr, 1996). Mortlity ws nlysed y the method of Kpln nd Meier (1958) using 1 or 0 s the fish survived or died, respetively, etween the time intervls, followed y the generi test of Wi1oxon (Gehn, 1965). Results In ll trils nd for ll groups the highest mortlity rises during the first month (Tle 1). In fish trnsferred to sewter, the mortlity inresed nd rehed mximum vlues of.1 nd.2 % for trils 1 nd 3. Tle 1 Cumultive mortlity (%) of tlnti slmon juveniles from tril 1, 2 nd 3 (ges 1 +, 1.5 +, nd 2 +, respetively), rered up to 0 dys. Period (dys) 0-30 30-60 60-90 90-0 Totl Freshwter 1 + (n = 295) 3.1 0.7 1.1 1.7 6.6 1.5 + (n = 328) 3.7 1.8 0.9 6.4 2 + (n = 272) 1.8 1.1 1.5 1.1 5.5 Sewter 1 + (n = 288) 7.2 2.8 1.4 0.7.1 1.5 + (n = 320) 4.1 2.2 1.9 8.2 2 + (n = 275) 8.4 2.5 1.5 1.8.2 ll results onsist of two replite tnks nd n denotes numer of fish in eh experimentl group. Different letters within eh olumn denote differenes (Kpln nd Meier (1958) method, followed y the generi test of Wi1oxon, p < 0.05). Tril 1 (smolts 1 + ) Plsm osmollity vlues were similr oth in freshwter nd sewter (p > 0.05) over the first 60 d. In ontrst, there were differenes (p < 0.001) in the lst two smpling points (dys 90 nd 0), with the mximum vlues eing registered in the sewter group (Figure 2). Exept for dy 30, where plsm hloride levels were identil in oth experimentl groups, this prmeter ws ffeted y sewter exposure, with vlues 3 to 8 % higher nd (p < 0.001) omprtively to the freshwter group (Figure 2). The ondition ftor (CF) presents n initil vlue of 0.883 ± 0.037 nd hnges similrly in oth groups, with derese in the first 30 d nd onsistent inrese from this point onwrds. t the end of tril 1, the group mintined in freshwter presents vlue 20 % higher (p < 0.001) thn the group trnsferred to sewter (Figure 2C). oth groups (freshwter nd sewter) onsistently inrese the individul weight during the 0 dys of the study. Differenes (p < 0.001) in growth were only oserved t dy 30, with fish kept in freshwter eing 8.5 % hevier. fter this smpling point, fish in sewter presented higher SGR (p < 0.05) thn the group in freshwter (Tle 2). The weight inrese for oth freshwter nd sewter groups ws lwys higher (p < 0.05) in tril 1, omprtively to trils 2 nd 3 (Figure 3 nd ). Tril 2 (smolts 1.5 + ) During the prodution of out-of-seson smolts, differenes (p < 0.05) were oserved in plsm osmollity, hloride levels nd CF within eh photoperiod regime, LN or LD (Figure 4, nd C). These prmeters differ (p < 0.001) etween oth groups, either in the freshwter phse or fter sewter trnsfer of the LD group. During the freshwter phse, differenes in plsm osmollity were registered (p < 0.01) etween the two groups (LN nd LD) t the time of photoperiod reversl (dy 60), wheres prior nd fter tht reversl, this prmeter ws similr for oth groups. fter sewter trnsfer (eginning of tril 2) this prmeter nd the plsm hloride onentrtion were lwys higher (p < 0.001) in fish kept in sewter. Si. gri. v.70, n.1, p.-20, Jnury/Ferury 2013
15 Gonçlves et l. Yer-round prodution of pn-sized slmon Osmollity (mosm kg 1 ) 360 350 340 330 320 3 300 Fresh wter Se wter Durtion (dys) Weight gin (%) 250 200 0 50 0 1+ 1.5+ 2+ Durtion (dys) Fresh wter Se wter 250 1+ 1.5+ 2+ Chloride (mmol L 1 ) 0 130 Weight gin (%) 200 0 Condition ftor 0 1.3 1.2 1.1 1 0.9 0.8 0.7 C Durtion (dys) Durtion (dys) Fresh wter Se wter Figure 2 Tril 1: Temporl hnges in plsm osmollity (), hloride (), nd ondition ftor (C) of tlnti slmon Slmo slr rered during 0 dys in fresh nd sewter. Vlues re given s mens ± SE. Different letters within the sme smpling point indite signifint differenes (p < 0.05). The CF inreses similrly for oth groups during the first 60 dys of the preliminry stge. fter the reversl of photoperiod, the CF of the LD group dereses onsistently, presenting lower vlues in the eginning of tril 2 (p < 0.001) ompred to the LN group (Figure 4C). The group tht ws trnsferred to sewter presents no further hnges in the CF, wheres in the freshwter ontrol group the CF deresed shrply, presenting lower vlue t the end of the tril (p < 0.001) ompred to the oserved in the sewter fish. fter photoperiod reversl, in the prodution of out-of-seson smolts, the gill N +, K + -TPse tivity in the LD groups inresed progressively, with pek in Jn. (.6 ± 0.7 μmol P i mg 1 protein h 1 ) nd just efore 50 0 Durtion (dys) Figure 3 Reltionships etween the perentges of live weight gin of tlnti slmon Slmo slr in trils 1, 2 nd 3 (yer lsses 1+, 1.5+ e 2+, respetively) rered during 0 dys in fresh () nd sewter (). Vlues re given s mens ± SE. Different letters within the sme smpling point indite signifint differenes (p < 0.05). the sewter trnsfer. In ontrst, the LN group remins with onstnt nd lower (p < 0.001) tivity vlue (Figure 5). lso, in this preliminry stge (first 60 d), LN fish presented higher men weight (p < 0.001) ompring to fish on short-dy photoperiod. Two months fter the photoperiod reversl, fish on the LD group presented higher (p < 0.001) men weight when ompred with the LN fish (Tle 3). Growth during the seond phse of the tril differs etween groups (p < 0.001). However, t the end of the tril period, the group kept in freshwter hd greter weight gin lthough the finl verge weights were similr for oth slinity regimes (Tle 2). Tril 3 (smolts 2 + ) Throughout tril 3, differenes in plsmti osmollity, hloride nd CF were oserved for oth freshwter nd sewter groups (Figure 6, nd C). In ll smpling points the levels of the plsmti osmollity nd hloride were lwys higher (p < 0.05) in the group trnsferred to sewter. t the end of tril 3, fish kept in freshwter showed CF vlue (0.98 ± 0.02) out % higher (p < 0.001) ompred to fish trnsferred to sewter, s oserved in tril 1. oth experimentl groups presented n overll inrese in growth during the 0 Si. gri. v.70, n.1, p.-20, Jnury/Ferury 2013
Gonçlves et l. Yer-round prodution of pn-sized slmon Tle 2 Men weight nd speifi growth rte (SGR) of tlnti slmon juveniles from tril 1, 2 nd 3 (ges 1 +, 1.5 + nd 2 +, respetively) rered up to 0 dys. Freshwter Dy 0 Dy 30 Dy 60 Dy 90 Dy 0 Weight (g) 89.5 ± 1.0 111.1 ± 2.3 138.6 ± 2.4 190.5 ± 3.7 255.0 ± 3.6 SGR (% ody weight dy 1 ) - 0.86 ± 0.01 0.92 ± 0.02 0.90 ± 0.02 0.98 ± 0.01 n 139 54 54 59 96 Sewter Weight (g) 83.1 ± 0.8 2.4 ± 1.5 136.9 ± 2.1 184.0 ± 2.6 253.6 ± 2.8 SGR (% ody weight dy 1 ) - 0.66 ± 0.02 0.97 ± 0.02 0.96 ± 0.02 1.03 ± 0.01 n 1 53 51 57 91 Freshwter Weight (g) 154.5 ± 1.0 186.4 ± 3.3 245.1 ± 4.3 3.5 ± 3.1 - SGR (% ody weight dy 1 ) - 0.62 ± 0.01 0.81 ± 0.01 0.90 ± 0.01 - n 3 50 50 3 - Sewter Weight (g) 156.0 ± 0.8 181.9 ± 2.7 237.9 ± 3.3 300.3 ± 2.6 - SGR (% ody weight dy 1 ) - 0.47 ± 0.01 0.86 ± 0.01 0.84 ± 0.01 - n 8 50 50 6 - Freshwter Weight (g) 132.4 ± 1.7 9.5 ± 3.6 194.1 ± 4.9 235.4 ± 5.1 294.2 ± 3.9 SGR (% ody weight dy 1 ) - 0.65 ± 0.01 0.64 ± 0.02 0.68 ± 0.01 0.70 ± 0.01 n 6 28 33 31 75 Sewter Weight (g) 9.2 ± 1.2 136.7 ± 3.4 171.7 ± 4.0 213.5 ± 4.7 255.4 ± 2.8 SGR (% ody weight dy 1 ) - 0.34 ± 0.01 0.61 ± 0.03 0.68 ± 0.01 0.67 ± 0.01 n 32 36 31 1 Vlues re given s mens ± SE; n denotes numer of individully tgged fish in eh experimentl group. ll results onsist of two replite tnks. Different letters in eh olumn within eh tril denote differenes (One-wy NOV, Sheffé s multiple omprisons, p < 0.05). Tril 1 Tril 2 Tril 3 Tle 3 Men weight of tlnti slmon (Slmo slr) juveniles in tril 2 (1.5 + ), rered up to 0 dys in freshwter with nturl photoperiod (LN) nd photoperiod-indued prr-smolt trnsformtion (LD). Dy 0 Dy 30 Dy 60 Dy 90 Dy 0 Weight (g) 78.8 ± 0.5 90.2 ± 1.1 111.6 ± 1.4 8.1 ± 1.6 151.3 ± 1.0 n 50 53 62 55 158 Weight (g) 80.3 ± 0.6 88.1 ± 1.2 5.0 ± 1.5 5.4 ± 1.4 2.8 ± 1.1 n 50 51 54 52 0 Vlues re given s mens ± SE; n denotes numer of individully tgged fish in eh experimentl group. ll results onsist of two replite tnks. Different letters within eh olumn denote differenes (One-wy NOV, Sheffé s multiple omprisons, p < 0.05). LN LD dys of the study. However, the weight gin inrement ws lower (p < 0.05) when ompred with trils 1 nd 2 (Figure 3 nd ). Fish mintined in freshwter showed enhned growth performne ompred to those kept in sewter in ll the smpling points (Tle 2), lthough the differenes were not lwys signifint. Disussion Hydro-minerl lne Mny slmonid speies hve disturnes in the hidro-minerl lne during the smoltifition period when kept in freshwter (Wedemeyer et l., 1980; MLeese et l., 1994; jörnsson et l., 2011). Those ltertions inlude dereses in the plsm osmollity (Kuo, 1955) nd in the plsm nd tissue hloride levels (Fontine, 1951; Houston nd Thredgold, 1963). The inrese in plsm osmollity nd hlorine onentrtion fter sewter trnsfer suggests n identil development of the osmoregultory pity in ll the ge lsses used in this study nd hs een desried efore (lkurn nd Clrke, 1987; Stgg et l., 1989; Hndelnd et l., 2003). However, if the osmoregultory pity is well developed, in few dys those prmeters strongly Si. gri. v.70, n.1, p.-20, Jnury/Ferury 2013
17 Gonçlves et l. Yer-round prodution of pn-sized slmon Osmollity (mosm kg 1 ) 360 350 340 330 320 3 300 LN LD 180 2 Durtion (dys) LN LD N+, K+-TPse (umoles Pi mg protein 1 h 1 ) 20 15 5 0 LN LD Septemer Otoer Novemer Deemer Jnury Chloride (mmol L 1 ) Condition ftor 0 130 0 1.3 1.2 1.1 1 0.9 0.8 0.7 C 180 2 Durtion (dys) 180 2 Figure 4 Tril 2: Chnges in plsm osmollity (), hloride (), nd ondition ftor (C) of tlnti slmon Slmo slr rered during 2 dys in freshwter, either under nturl photoperiod (LN; 42 ºN) or in n winter/spring photoperiod (LD; L8:D6/L:D8). The rrow indites when fish were trnsferred from fresh to sewter. From dy 0 to 2, ll fish were kept under nturl photoperiod. Vlues re given s mens ± SE. Different letters within the sme smpling point indite signifint differenes (p < 0.05). deline, stilizing t levels slightly higher thn those found in fish kept in freshwter (Stgg et l., 1989; Usher et l., 1991). Hndelnd et l. (1998) demonstrted tht hlorine plsmti onentrtion of fish mintined in sewter is pproximtely 8 % to % higher thn in fish kept in freshwter. The overll results in the present study re in greement with this oservtion. During the first 30 d of trils 1 nd 3 ll the groups showed redution in the ondition ftor (CF). This ws n effet of smoltifition in tril 1 nd of sewter trnsfer in tril 3, with the CF vlues eing in greement with the vlues previously ited (Stefnsson et l., 1991; Solkken et l., 1994; Dunn et l., 1998). During the preliminty stge of tril 2, CF in fish sumitted to om- Durtion (dys) LN LD Figure 5 Tril 2: Temporl hnges of rnhil N +, K+-TPse tivity of tlnti slmon Slmo slr rered during 0 dys in freshwter, either under nturl photoperiod (LN; 42 ºN) or in n winter/spring photoperiod (LD; L8:D/L:D8). Vlues re given s mens ± SE. Different letters within the sme smpling point indite signifint differenes (p < 0.05). pressed (winter/spring) photoperiod showed n initil inrese similr to fish sumitted to nturl photoperiod. However, when the mount of dily light strted to inrese (photoperiod reversl), CF deresed onstntly until the end of the preliminry stge. During tril 2, the fish showed similr profile of CF evolution s fish in tril 1 nd 3. These results re in greement with those of previous studies in whih similr photoperiod regimes were used (Stefnsson et l., 1991; Solkken et l., 1994). The N +, K + -TPse results (.6 μmol P i mg 1 protein h 1 ) otined in the preliminry stge of tril 2, grees with previous studies (Gignon nd Quémener, 1992; Sigholt et l., 1998). It is oherent when ompred to vlues oserved in smolts of the upper modl group, whih present good limtion pity to high slinity in the norml trnsfer seson (Gignon nd Quémener, 1992; Reis-Henriques et l., 1996). Growth In tril 2 (ge 1.5 + ) growth differenes were oserved during the preliminry stge. These results re supported y previous studies on the sesonl modifitions relted to the photoperiod yle. Light regimes with two months of short dys redued fish growth (Skilrei et l., 1997; Dunn nd romge, 1998), while ontinuous illumintion or extensive dy-length inresed growth (Sunders et l., 1985; MCormik et l., 1987; Solkken et l., 1994; Sigholt et l., 1998). The overll deline in growth performne of fish kept under redued photoperiod is however ompensted in the following months fter the photoperiod were reversed. Moreover, Hnsen et l. (1992) demonstrted tht fish sumitted to ontinuous light hs doule growth indexes ompring to fish mintined under nturl photoperiod. lthough ontinuous light ws not used during tril 2, Si. gri. v.70, n.1, p.-20, Jnury/Ferury 2013
18 Gonçlves et l. Yer-round prodution of pn-sized slmon Osmollity (mosm kg 1 ) Chloride (mmol L 1 ) Condition ftor 360 350 340 330 320 3 300 0 130 0 1.3 1.2 1.1 1 0.9 0.8 0.7 C Durtion (dys) Fresh wter Se wter Figure 6 Tril 3: Temporl hnges in plsm osmollity (), hloride (), nd ondition ftor (C) of tlnti slmon Slmo slr rered during 0 dys in either fresh or sewter. Vlues re given s mens ± SE. Different letters within the sme smpling point indite signifint differenes (p < 0.05). high growth inrement ws oserved in fish sumitted to long dys fter photoperiod reversion, with growth rtes 30 to 70 % higher thn fish on nturl photoperiod (LN). Studies rried out in ges (Krkenes et l., 1991; Nole et l., 2008) nd in tnks (ergheim nd Forserg, 1993) showed tht prolonging the feeding hours from nturl photoperiod to ontinuous light did not ffet the dily ingestion rtes in tlnti slmon. Sine in the present study, fish were lwys fed in regime orresponding to the sme intervl s in the tril with less illumintion, nd wter temperture ws ontinuously deresing until Jn. (Figure 1), we my onlude tht the photoperiod mnipultion is simple nd effetive method to inrese growth even t southern ltitudes with reltive high tempertures. Durtion (dys) Fresh wter Se wter Durtion (dys) Fresh wter Se wter Exept for tril 3 with smolts 2 +, differenes in growth etween freshwter nd sewter groups were not deteted, whih is in ordne with results from previous studies (Duston, 1994; Jorgensen nd Joling, 1994; Dmsgrd nd rnesen, 1998). Compring the results for ll trils, it ws oserved tht for oth freshwter nd sewter groups, the smolts 1 + hd higher weight inrese, followed y smolts 1.5 + nd 2 +. Smolts 1 + were from n upper modl lss nd in tlnti slmon, fish tht elong to this lss usully present higher growth nd metolism (Thorpe et l., 1980; Skilrei nd Hnsen, 2004). Furthermore, y ompring the growth in freshwter etween ll experimentl groups it is ler tht fish in tril 2 took dvntge of therml positive differentil (5-6 C). The length of initil growth depression oserved in the present study grees with Jorgensen nd Joling (1994), tht desried redution in food ingestion nd growth in fish during the first d fter sewter trnsfer, ut fter one month these prmeters resumed the levels oserved in freshwter. Other uthors hve oserved growth depression during one week (Dmsgrd nd rnesen, 1998) to over month (Usher et l., 1991; Hndelnd et l., 2003; lne et l., 2011), lrgely exeeding the ritil osmo-regultion period. ll these differenes reflet the speifi hrteristis of eh tril nd their multiple intertive vriles. rnesen et l. (1998) demonstrted in tlnti slmon strong orreltion etween sewter trnsition nd temperture, on food ingestion nd growth performne. The slinity redution imposed in the present study lerly ontriuted for the positive performne of the fish, otherwise verge sewter tempertures nerly 18 C, in the first month fter trnsfer, would ertinly indued osmoti disturnes with negtive reflexes in the growth nd mortlity, s demonstrted y Hndelnd et l. (2000) nd Gonçlves et l. (2006). Glreth nd Thorgrd (1995) working with S. slr of 1 g, otined speifi growth rte of 0.52 % dy 1 fter 376 d. Dunn et l. (1998) working with 0+, 1+ nd nturl smolts trnsferred to sewter in Nov., De. nd pr., respetively, otined speifi growth rte etween 0.9 % nd 1 % dy 1 fter months of trnsfer in fish held t the highest tempertures (up to C). Imslnd et l. (2011) lso reported similr vlues. Hndelnd et l. (1998) working with 65 g slmons, showed tht the iomss ws duplited in three months t 8 C. It ws lso reported y these uthors tht the speifi growth rte during the first 23 dys ws redued ompring to the vlues oserved t the end of the seond nd third month, similrly to the present study. Therefore, if we exlude the poor weight gin during the first month in oth slinity onditions, we n onlude tht the growth performnes otined herein my e onsidered s stisftory. Indeed, Hndelnd et l. (2000) demonstrted the speifi growth rte is poor (0.18 % dy 1 ) in slmon rered t ove 18 ºC nd t full slinity. The growth rtes reported y ustreng et l. (1987) grossly exeeds the ones reported Si. gri. v.70, n.1, p.-20, Jnury/Ferury 2013
19 Gonçlves et l. Yer-round prodution of pn-sized slmon in the present study, ut they used the est results from multiple trils, wheres Hndelnd et l. (2008) reported t 6,, nd 18 C growth rtes of 0.78, 1.35, 1.53 nd 1.29 % dy 1, with different omposition of reruited fish (smolts 0 + ). lthough our trils were performed t lower tempertures, it ws onluded tht the redution of slinity ws entrl for the outome results. The ft tht ll fish were sumitted to frequent mnipultions whih ould hve hd n ute or hroni stress effet (Pikering, 1993) only reinfores this onlusion. The high mortlity during the first month fter trnsfer to sewter oserved in the present study reflets the diffiulty of fish in mintining the osmoti lne, ut my lso e n effet of exessive mnipultion during the tgging proedure. In ft, the fish lots kept in freshwter lso presented the highest mortlity during the sme period. The highest mortlities oserved in tril 1 nd 3 in the groups trnsferred to sewter re the onsequene of high wter temperture during the trnsition period. Furthermore, previous studies lso reported higher mortlity in S. slr juveniles ssoited with off-seson trnsfers (Thrush et l., 1994; Sigholt et l., 1995). In the present study, nd similrly to the results of Dunn et l. (1998), it ws oserved tht the 1.5 + group trnsferred in Jn. hd etter survivl rte. This suggests tht the ompressed photoperiod ws effetive in the prr -smolt trnsformtion nd tht oeni wter tempertures in the north Ierin ostl zone did not limit performne. In onlusion, it n e estimted rering period of three to four months fter sewter trnsfer to produe smolts 1.5 + or 1 + of ommeril pn-sized slmon (out 300 g). If smolts 2 + re used, the growth rtes re lwys lower thn 0.7 % nd this implites tht four months re neessry to reh the ommeril size, lthough smolts 2 + generlly hve twofold the men weight of smolts 1 +. This period ould e very importnt for mrketing resons s three months is the minimum residene time in sewter for fish to develop the typil smolt pigmenttion (Hnsen, 1997). Referenes lne, H.; Oehme, M.; Thomssen, M.; Terjesen,.; Rørvik, K. 2011. Redued growth, ondition ftor nd ody energy levels in tlnti slmon Slmo slr L. during their first spring in the se. quulture Reserh 42: 248 259. rnesen,.m.; Johnsen, H.K.; Mortensen,.; Joling, M. 1998. limtion of tlnti slmon (Slmo slr L.) smolts to old se wter following diret trnsfer from freshwter. quulture 8: 351 367. ustreng, E.; Storekken, T.; sgrd, T. 1987. Growth rte estimtes for ultured tlnti slmon nd rinow trout. quulture 60: 157 0. ergheim,.; Forserg, O.I. 1993. ttempts to redue effluent lodings from slmon frms y vrying feeding frequenies nd mehnil effluent tretment. p. 115 4. In: rne, G.; Kestemont, P., eds. Prodution, environment nd qulity. Europen quulture Soiety, Ghent, elgium. jörnsson,.th.; Stefnsson, S.O.; MCormik, S.D. 2011. Environmentl endorinology of slmon smoltifition. Generl nd Comprtive Endorinology 170: 290 298. lkurn, J.; Clrke, W.C. 1987. Revised proedure for the 24 h sewter hllenge test to mesure sewter dptility in juvenile slmonids. Cndin Tehnology Reports on Fisheries nd quti Siene 1515: 1 35. rett, J.R. 1979. Environmentl ftors nd growth. p. 599 675. In: Hor, W.S.; Rndll, D.J.; rett, J.R., eds. Fish physiology. demi Press, New York, US. Dmsgrd,.; rnesen,. 1998. Feeding, growth nd soil intertions during smolting nd sewter limtion in tlnti slmon, Slmo slr L. quulture 8: 7. Dunn, N.J.; uhinhie, N.; Roertson, D.; Murry, R.; romge, N. 1998. Growth, mturtion nd survivl of outof-seson 0 + nd 1 + tlnti slmon (Slmo slr) smolts. quulture 8: 325 339. Dunn, N.J.; romge, N. 1998. The effet of different periods of onstnt short dys on smoltifition in juvenile tlnti slmon (Slmo slr). quulture 8: 369 386. Duston, J. 1994. Effet of slinity on survivl nd growth of tlnti slmon (Slmo slr) prr nd smolts. quulture 1: 115 4. Fitzgerld, R.; Stefnsson, S.O.; Grforth, D.; Irwin, S. 2002. Prodution II: From egg to mrket size: onrering in freshwter nd mrine environments. p. 65 4. In: Sted, S.M.; Lird, L., eds. Hndook of slmon frming. Prxis, erlin, Germny. Fontine, M. 1951. Derese of the hlorine ontent of musle of young slmon (smolt) t the time of downstrem migrtion. Comptes Rendus de l démie des Sienes 232: 2477 2492 (in Frenh). Gignon, J.L.; Quémener, L. 1992. Influene of erly thermi nd photoperiod ontrol on smoltifition in tlnti slmon (Slmo slr). quti Living Resoures 5: 185 195. Glreth, P.F.; Thorgrd, G.H. 1995. Sltwter performne of ll-femle triploid tlnti slmon. quulture 138: 77 85. Gehn, E.. 1965. generlized Wiloxon test for ompring ritrrily singly-ensored smples. iometrik 52: 203 213. Gonçlves, J.; Crrç, S.; Dmseno-Oliveir,.; Fernndez- Durn,.; Diz, J.; Wilson, J.; Coimr, J. 2006. 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Thorpe, J.E.; Morgn, R.I.G.; Ottwy, E.M.; Miles, M.S. 1980. Time of divergene of growth groups etween potentil 1+ nd 2+ smolts mong siling tlnti slmon. Journl of Fish iology 17: 13 21. Thrush, M..; Dunn, N.J.; romge, N.R. 1994. The use of photoperiod in the prodution of out-of-seson tlnti slmon (Slmo slr) smolts. quulture 1: 29 44. Usher, M.L.; Tlot, C.; Eddy, F.. 1991. Effets of trnsfer to sewter on growth nd feeding in tlnti slmon smolts (Slmo slr L.). quulture 94: 309 326. Wedemeyer, G..; Sunders, R.L.; Clrke, W.C. 1980. Environmentl ftors ffeting smoltifition nd erly mrine survivl of ndromous slmonids. Mrine Fisheries Reviews 42: 1 Zr, J.H. 1996. iosttistil nlysis. Prentie-Hll, Upper Sddle River, NJ, US. Si. gri. v.70, n.1, p.-20, Jnury/Ferury 2013