Thermal and pH tolerance of farmed, wild and first generation farmed-wild hybrid

salmon (Salmo salar)

D. Hamoutene, L. Lush, I. Costa, K. Burt, J. Perez-Casanova, J. Caines

Fisheries and Oceans Canada, Northwest Atlantic Fisheries Center, NL, CanadaNorthern Harvest Sea Farms Ltd., NL, Canada

In the study of salmon farmed-wild interactions, the degree of adaptation of local populations and the magnitude of genetic differentiation between wild and farm salmon within a geographical area suggest the need for a case by case approach. In Newfoundland, farm salmon are originally from St. John River strain (New Brunswick) and might lack local adaptations to Newfoundland rivers, and in particular to acidic river water.

Risk assessment of the potential effect of farming on wild populations

Level of genetic introgression of farmed salmon in some of the local population

Differences in fitness/local adaptations between farmed, wild and hybrids

Hutchings (1991) predicted that the effect of interactions with wild population depends on 1) the degree of local adaptations, 2) genetic differentiation between wild and farmed, 3) the magnitude of outbreeding depression, and 4) the size of the wild population. It is important to adopt a case-dependent approach when assessing the effects that a given farmed populations may have on the persistence of a particular wild population (Weir et al., 2004).

Spatial and temporal distribution of farmed Atlantic salmon after experimental release from sea cages locations.

RIVER

Farmed escapees

Wild Salmon

Mating Behaviour

-Male aggression lower in farmed (Stead and Laird 2002)

-Breeding behaviour less efficient in farmed (Fleming 1996a)

-Nest construction less efficient in farmed (Fleming et al. 1996)

-More nest destruction in farmed (Fleming et al.1996)

Physical Factors- pH (Parker and McKeown 1987; Peterson et al 1980; Kitamura and Ikuta 2000; Fraser et al. 2008): effect of low pH on spawning, survival of F1 hybrids as well as sperm and eggs

- Temperature ( Gunnes 1979; Beachamand Murray 1987): effect of low and fluctuating temperatures on egg survival.

Mating

Behaviour-Migratory behaviour ( Jonsson et al. 1990; Økland et al. 1995; Thorstad et al. 1998)

- Farmed salmon swim up river at later dates than wild spawners and swim back to sea sooner.

Spawning / Gamete quality-Spawning Success: farmed females retained more eggs (Fleming et al. 2000)

-Higher protein, lipid, carbohydrate and energy in eggs from wild females (Srivastava and Brown 1991)

Successful CrossesWildxWild vs WildxFarmed vs FarmedxFarmed

-Fertilization success

-Egg mortality

-Eyed Eggs

-Hatching

Fitness and survival of progeny

Gamete qualitySpermeggs

In Conne river (Nov-Feb)Temp: -0.11-12.61 ºCpH: 4.61- 6.24 ºC

It is important to put results in the general context – This study does not take into account the odds of farmed and wild fish “meeting” and mating in river conditions

Reproduction trials between wild and farmed salmon in Newfoundland

- Documenting gamete quality parameters in wild and farmed salmon (different populations (NB, NL), different genetic origin and initial rearing environments)

- Determining reproductive success when mating farmed and wild salmon

- Determining the effect of river water on farmed fish gametes’ potential to cross successfully with wild fish eggs and sperm

Gamete quality

Differences in sperm metabolism and morphology between wild and non-local farmed Atlantic salmon, Salmo salar were assessed by measuring metabolic enzymatic activities and length of sperm flagella. No differences were observed between wild and farmed salmon sperm with regards to cell counts or any of the biochemical parameters assessed. Flagella of sperm cells were significantly longer in wild than farmed salmon; however this did not result in higher energy levels or different fertilization rates.

N. Camarillo-Sepulveda, D. Hamoutene, Lush L., Burt K., Volkoff H., & Fleming I. A. Sperm traits in farmed and wild salmon Salmo salar (Linnaeus 1758). Submitted to Journal of Fish Biology.

Gamete quality

There was no differential survival of pure wild, pure farm, and hybrid embryos up to the eyed stage in river water.

A comparison of early life traits in hatchery conditions (i.e. genetic differences) show that the wild females’ progeny hatched earlier, and had higher total lengths at hatch and at yolk sac reabsorption than pure farm larvae.

Our findings also suggest no differential survival of hybrids in tank/hatchery conditions when compared to pure wild progeny up to 70 dph (hybrids with farm mothers have higher mortalities than pure farm and other hybrids and might be less likely to survive in the early stages due to delayed hatch).

Early life traits

Fitness of progeny/hybrids - Degree of local adaptation1- Effect of low river pH

• While adverse genetic changes due to hybridization between farmed and wild salmon might not be manifested until the second generation (F2), the existence of F2 or later generations depends ultimately on the survival of F1 hybrids.

• We tested the hypothesis that wild Atlantic salmon from South coast Newfoundland waters are more adapted to low pH by comparing survival, growth and gill Na+, K+ -ATPase activity of wild, farmed and wildXfarmed hybrid salmon parr in a common garden experiment.

• 360 0+ salmon parr were equally split into six 273L tanks supplied with filtered recirculating freshwater: 3 neutral pH (pH: 7.0), 3 low pH (pH: 4.9 -5.1)

• Parr were distributed into tanks using three families for each of the four cross types (WXW, FMXWF, WMXFF, FXF; n=5 individuals/family in each tank)

• Water pH, ammonia, oxygen, and temperature were monitored daily• Fed 2% of body mass daily. Feed consumption was assessed by

weighing feed prior to and after feeding, and weighing feed pellets remaining in the tank 10 minutes following presentation of the feed.

The study design

• pH was lowered to ~5.0 daily in each low pH tank, through acidifying the water used for daily water exchange with sulphuricacid.

• Fish were assessed daily for survival, and bi-weekly for mass and length.

• At the end of 90 days, all fish were euthanized, weighed, measured and gill arches excised to assess Na+, K+ ATPase activity

• One-way ANOVAs were employed to determine effects of treatment (neutral/low pH) on each cross type (FMXWF, WXW, WMXFF, FXF) for specific growth rate (SGR), condition factor (CF), cumulative mortality and gill Na+,K+-ATPase activity

Mean (± SD) specific growth rate, condition factor, mortality and ATPase content of Atlantic Salmon parr

reared in neutral and low pH freshwater.

pH significantly affected most parameters within tanks (lower SGR, CF and Na+, K+-ATPase activity) and caused greater mortality.

Neutral pH Low pHSpecific Growth Rate

(g.d-1) 1.29 ± 0.24 a 1.12 ± 0.26 b

Condition Factor 1.15 ± 0.14 a 1.11 ± 0.11 b

Cumulative Mortality 9.0 ± 15.6 a 20.0 ± 7.0 aNa+,K+-ATPase (umol /

mg protein hour ) 2.725 ± 2.423 a 1.162 ± 0.539 b

Numerical difference in SGR (g.d-1) between treatments for each of the four cross types of

Atlantic Salmon parr reared in neutral and low pH

Cross Type SGR Neutral

SGR Low pH Difference P-Value

FMXWF 1.36 1.22 0.14 0.089

WXW 1.25 1.13 0.12 0.336

WMXFF 1.26 1.08 0.18 0.041*

FXF 1.29 1.05 0.24 <0.001*

Numerical difference in Na+,K+-ATPase activity between treatments for each of the four cross types of Atlantic

Salmon parr reared in neutral and low pH

Cross Type

ATP-aseNeutral

ATP-aseLow pH Difference P-Value

FMXWF 2.36 1.133 1.227 <0.001

WXW 2.258 1.199 1.059 <0.001

WMXFF 2.31 1.096 1.214 <0.001

FXF 3.913 1.228 2.685 <0.001

The effect on survival of low pH treatment within cross type did not reveal any significant differences (P=0.350). However a trend was observed that higher mortality occurred in crosses created with farmed females and exposed to the low pH conditions (FXF and WMXFF).

% Mortality for each of the four cross types of Atlantic salmon parr reared in neutral

and low pH (Mean ±SD)

Crosstype Neutral pH Low pH

FMXWF 4.7±8.1 13.3±6.5

WXW 6.7±11.5 15.7±10.3

WMXFF 17.7±30.6 22.3±8.1

FXF 6.7±11.5 29.0±20.3

Conclusions

• Low pH significantly affected all the parameters measured• The groups mostly affected by low pH were the crosses

generated with farmed females (farmed, WMXFF) with significant ly lower SGR and a trend towards lower survival

Hamoutene D., Costa I., Burt K., Lush L., and Caines J. Survival of farmed, wild and first generation hybrid Atlantic Salmon (Salmo salar), to low temperatures following seawater transfer. Journal of Applied Ichthyology, in press.

After smoltification, cold spring seawater temperatures (1.5 to 5°C) such as those observed on the south coast of Newfoundland can be problematic to salmon as the combination of abrupt seawater exposure and cold temperature is known to overwhelm osmoregulatorymechanisms. In this study, we hypothesize that F1 hybrids might be less adapted to seawater migration in cold temperatures post-smoltificationand could experience higher mortalities than their wild counterparts.

Fitness of progeny/hybrids - Degree of local adaptation2- Cold spring temperatures

In November 2013, 1751 PIT tagged juvenile Atlantic Salmon (+1, ~70g, ~19cm), representing the four cross types (WXW, n= 6 families; FXF, n= 7; FFXWM, n= 4; WFXFM, n= 8), were distributed into four 4000L flow through cylindrical tanks.

WFXFM(n=8)

FXF(n=7)

WXW(n=6)

FFXWM(n=4) Totals

Tank 1 177 119 121 32 449

Tank 2 147 144 112 26 429

Tank 3 136 187 82 27 432

Tank 4 151 183 87 20 441

WFXFM (n=8) FXF (n=7) WXW (n=6) FFXWM (n=4) P values*

Tank 1 26.15 ± 15.96 21.75 ± 19.06 52.36 ± 22.34 40.13 ± 40.61 0.061

Tank 2 34.91 ± 15.34 17.74 ± 12.51 43.93 ± 19.09 30.95 ± 35.95 0.118

Tank 3 10.48 ± 8.98 14.10 ± 8.65 32.77 ± 22.89 9.00 ± 11.33 0.062

Tank 4 10.69 ± 13.51 11.28 ± 12.28 13.63 ± 11.71 8.04 ± 11.80 0.767

*One way ANOVA or Kruskal-Wallis ANOVA on ranks, number of families per cross-type is provided between brackets

Total mortalities (%) of Atlantic salmon juveniles in all four cross types: WFXFM; FXF; WXW; FFXWM and tanks (means and standard deviations are listed even for data not normally distributed). Mortalities were recorded daily.

- No differences in mortality among the four salmon cross types. When grouped together hybrid smolts tolerated cold temperatures even better than wild ones (contrasts with Handelandet al. (2003) where wild salmon smolts were better able to tolerate seawater transfer than the hatchery strain even at low temperatures).

- Our findings suggest that F1 hybrids resulting from crossing wild salmon and farmed St John River salmon are as likely to survive seawater migration in cold temperatures as their wild counterparts (similar to Fleming et al. (2000) who found no differences in the relative survival to maturity of farmed, native and farm X native offsprings).

Conclusions• Wild females have bigger eggs than farmed ones while no functional differences were found

in sperm.

• No differential survival of pure wild, pure farmed, and hybrid embryos up to the eyed stage in river water.

• Wild females’ progeny hatched earlier, and had higher total lengths at hatch and at yolk sac reabsorption than pure farm larvae (maternal influence).

• Our common garden experiments have revealed [As environmental variability is eliminated, any differences found in performance (survival and growth in this study) will reflect genetic differences (with the exception of maternal physiological effects) (McGinnity et al., 2003)] :

Potential effects of low pH on growth and survival on F1 hybrids with farmed mothers [Mating between wild males and farmed females are suspected to be more prevalent in the wild (Fleming et al 2000)].No differential effect of cold spring temperatures (shortly after smoltification) on survival of wild, farmed and F1 hybrids.