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Growth, Mortality, Recruitment and Yield of Rainbow Trout, Oncorhynchus mykiss Walbaum, 1792 in Karacaoren-I Dam Lake, Turkey




Growth, Mortality, Recruitment and Yield of Rainbow Trout, Oncorhynchus mykiss Walbaum, 1792 in Karacaören-I Dam Lake, Turkey

Mehmet Cilbiz1* and F. Banu Yalim2

1Fisheries Research Institute, Eğirdir, Isparta-32500, Turkey

2Mediterranean Fisheries Research, Production and Training Institute, Kepez Unit, 07192, Antaya, Turkey


In this study, growth parameters (i.e. condition factor, length-weight relationship, K, L, to), mortality rate (Z, M, and F), recruitment pattern and yield were investigated for Oncorhynchus mykiss in Karacaören I Dam Lake. Fish were collected on monthly basis between July, 2013 and June, 2014. Growth parameters were analyzed by ELEFAN with monthly length–frequency data. The b values of the length-weight relationship, mean condition factor, K (growth coefficient), L(asymptotic length) and to were estimated as 3.207, 1.13, 0.33 year-1, 36.50 cm and -0.476 years, respectively. Total mortality (Z) by length-converted catch curve was estimated at 0.83 year-1, fishing mortality (F) 0.14 year-1, natural mortality (M) 0.69 year-1 and exploitation rate (E) 0.17. According to the result of Relative Yield/Recruit analysis estimated Emax>E, so in this context stock of O. mykiss was not overexploited in Karacaören I Dam Lake.

Article Information

Received 03 August 2016

Revised 27 August 2016

Accepted 30 September 2016

Available online 26 April 2017

Authors’ Contributions

Both authors conceived and designed the study. MC collected and analyzed data and wrote the article.

Key words

Oncorhynchus mykiss, Rainbow trout, Length-weight relationship, Condition factor, Recruit analysis, Van Bertalanffy growth curve.


* Corresponding author:

0030-9923/2017/0003-0825 $ 9.00/0

Copyright 2017 Zoological Society of Pakistan



Native range of Oncorhynchus mykiss is the Eastern Pacific Ocean and the freshwaters, mainly west of the Rocky Mountains, from northwest Mexico (including extreme northern Baja, California) to the Kuskokwim River, Alaska. It is probably native in the drainages of the Peace and Athabasca rivers east of the Rocky Mountains (MacCrimmon, 1971; NOBANIS, 2015). Nowadays except for certain parts of tropical areas it has reached a global distribution area throughout the world. This distribution is based on human activity such as amateur fishing and aquaculture. O. mykiss was brought from Germany at first in 1970. Then its aquaculture started in Turkey (Çetinkaya, 2006). This fish is now distributed over large areas of Turkey’s inland waters due to the proliferation of aquaculture locations. This fish is included in IUCN’s (International Union for Conservation of Nature) list of 100 World’s Worst Invasive Alien Species, though Çetinkaya (2006) has reported that there is no invasive risk of O. mykiss because of its inability to create fertile population in Turkey. On the contrary, Küçük and İkiz (2004) have reported that this species has ability to reproduce in some natural waters of South-West Mediterranean region of Turkey. Similarly, Candiotto et al. (2011) have reported that in some cases, O. mykiss can constitute self-sustaining stable populations. Davis (2012) has likewise reported that hatchery raised rainbow trout have the ability to reproduce and become naturalized to reservoir systems and also wild rainbow trout are recruiting to the adult population in Deerfield Reservoir.

The population of O. mykiss is increasing year by year. The total production was 277 t in 2000, which increased to 438 t in 2013. This production contributed around 980,000 US$ in national economy (TUIK, 2015).

In the previous studies, Leiner (1995) studied growth, mortality and production of brown and rainbow trout in 32 sites on 15 streams of New Mexico. Candiotto et al. (2011) studied biology of one of the rare European spawning populations of O. mykiss in Italian stream. Korman et al. (2012) studied recruitment dynamics and movement of rainbow trout in the Colorado River in Grand Canyon using an integrated assessment model.

For evaluation of commercial fish stock we have studied here the growth, mortality, recruitment and yield of O. mykiss. It is hoped that the results of this study will improve our understanding of population dynamics of O. mykiss in Karacaören-I Dam Lake.


Materials and Methods

Study area

The Karacaören-I Dam Lake is located in limits of the cities Isparta and Burdur province (West South Anatolia) (Fig. 1). Surface of the lake is 45.5 km2, maximum depth is 65 m and altitude is 85 m (Ozvarol and Ikiz, 2009). Fish sampling was carried out on monthly basis, at two different stations with a total of 24 trials, during July 2013 and June 2014. Sampling station depths were between 6-9 m. Gillnets were made of monofilament material with 3.2, 4, 5, 6, 7, 8 and 9 cm stretched mesh sizes with 0.20 mm rope thickness and hanging ratio of 0.50. Depths of all nets were 50 meshes which were 100 m long for each panel. All nets were set in the afternoon and retrieved the following morning. The fork length (FL) of the fish was measured to the nearest 0.1 cm with a measuring board and weight recorded with 1g precision digital scale.



Length-weight relationship and condition factor

Fishes had nonlinear relationship between length and weight that can be expressed as W= aLb (Froese et al., 2011), where W= weight of the samples in g, L= length of the samples in cm, a and b are constant parameters of the regression equation. In the calculation of condition factor (C) the formula of Fulton’s coefficient of condition factors C = (W*100)/L3 (Ricker, 1975) was used.

Growth analysis

The FISAT II software (Gayanilo et al., 2005) was used to analyze the monthly length-frequency data. Estimates of the growth parameters, L (asymptotic length), and K (growth coefficient) for the von Bertalanffy growth function (VBGF), were derived from the length frequency data using the ELEFAN I routine incorporated in the FISAT II. Algorithms of the routine require that the L parameter is known, at least within a biologically acceptable range. Initial values of L were obtained using the Powell–Wetherall method as modified by Pauly and Soriano (1986).

The ELEFAN program uses a nonparametric method to fit the von Bertalanffy growth curve through modes. The best curve will pass through the maximum possible number of modes, and the goodness of fit index (Rn) is defined by Rn = 10ESP/ASP/10 (ESP: Explained Sum of Peaks, ASP: Available Sum of Peaks) (Ye et al., 2014).

The value of to was obtained from the equation Log (-to) = -(0.3922)-0.2752 log(L)-1.038 log(K) (Pauly, 1983). The standard growth index (ɸ) was used as a measure of overall growth performance (Moreau et al., 1986). The index is defined as ɸ ′= logK + 2 logL.

Estimation of mortality rates

Mortality was estimated for the total sampling period. Length-converted catch curve was used to estimate total annual instantaneous mortality rates (Z) (Memon et al., 2016). The right descending arm of this curve was fitted with a regression line. The regression equation has the form ln(N) = a + bt′, where N is the number of fish in pseudo-cohorts ‘sliced’ by means of successive growth curves, is the relative age of the fish in that pseudo-cohort, and b with the sign changed provides an estimate of Z. To obtain an independent estimate of natural mortality rate (M), the equation of Pauly (1980) log (M) = -0.0066-0.279 log (L) + 0.6543 log (K) + 0.4634 log (T) was employed. Here, T means annual habitat temperature (19.5 °C).

Estimation of recruitment pattern

Recruitment patterns were determined from the routine implemented in FISAT II, which involved backward projection of the length frequency data onto the time axis based on the estimated growth parameters (Moreau and Cuende, 1991; Ye et al., 2014).

Estimation of relative yield per recruit

The model of Beverton and Holt (1956) as modified by Pauly and Soriano (1986) was used to estimate relative yield-per-recruit (Yˈ/R) and relative biomass per-recruit (Bˈ/R) for O. mykiss. Both the ogive selection method and the knife-edge selection method were used. From these, the values of exploitation rate giving maximum relative yield-per-recruit (Emax) was estimated. Emax (exploitation rate producing maximum yield), E0.1 (exploitation rate at which the marginal increase of Yˈ/R is 10% of its virgin stock) and E0.5 (the exploitation rate under which the stock is reduced to half its virgin biomass) were computed through the first derivative of the function (Uneke et al., 2010).




In the fishing trial we caught 166 O. mykiss species fork lengths of which were between 13.6-34.5 cm. Generally, more samples were collected during winter months than in other seasons. O. mykiss could not be obtained in June, July and August. Monthly catch composition is given in Table I and length-frequency distribution is shown in Figure 2.

Figure 3 shows a nonlinear relationship between length and weight of O. mykiss population. Regression model parameters calculated as a= 0.006; b=3.207 [3.162-3.252], R2= 0.968 and0.001. Using these parameters in the equation (W=a*Lb) (Froese et al., 2011) and ultimately length-weight relationship equation gave the estimate as W=0.006*L3.207. In this study O. mykiss showed positive allometric growth pattern (b>3).

Mean condition factor of O. mykiss population in Karacaören-I Dam Lake was calculated as 1.13 (min.= 0.85, max.= 1.61 and SE= 0.01).

Powell-Wetherall plot of O. mykiss is shown in Figure 4. Black points in Figure 4A were used for the regression analysis (Y= 7.29+ (-0.220)*X, r2= 0.977, L=33.08 cm and Z/K= 3.538).


Table I.- Monthly catch composition of O. mykiss.

Sampling period N

Fork length

Total weight

Mean + SEM (Min - Max)

Mean + SEM (Min - Max)

Oct 2012 1

19.5 + 0.00 (19.5-19.5)

94.0+ 0.00 (94.0-94.0)

Nov 2012 6

25.8 + 0.3 (25.0-27.0)

194.5 + 2.4 (189.0-205.0)

Dec 2012 61

18.6 + 0.5 (13.6-29.5)

83.2 + 8.6 (33.0-321.0)

Jan 2013 25

17.6 + 0.3 (14.5-22.4)

56.3 + 3.0 (35.0-101.0)

Feb 2013 40

19.6 + 0.4 (15.3-29.5)

89.1 + 8.9 (40.0-315.0)

Mar 2013 7

21.0 + 1.6 (15.5-28.8)

141.3 + 34.7 (75.0-337.0)

Apr 2013 19

25.6 + 0.7 (18.0-31.8)

210.9 + 16.5 (76.0-383.0)

May 2013


28.5 + 1.2 (25.8-34.5)

330.3 + 43.0 (236.0-554.0)



The growth pattern, which was von Bertalanffy growth curves of O. mykiss is shown in Figure 5. Parameters of the von Bertalanffy growth equation were indicated by ELEFAN as Lt=36.50[1-exp-0.33(t+0.4760)] and Wt=583.87[1-exp-0.33(t+0.4760)]3.207 (L=36.50 cm FL, W=583.87 g, K=0.33 year-1, to=-0.4760 years, SS=8, SL=31.50, Rn=0.597 and ɸ=2.64).

In the population of O. mykiss, there was one recruitment peak in a year (Fig. 6). This peak was in June with 18.38% recruitment. Most of the recruitments occurred in spring (i.e. March 15.92%, April 15.63%, May 16.67%).

The computed length-at-first-capture L25, L50 (or Lc), and L75 were 13.84, 14.11 and 14.37 cm, respectively (Fig. 7). Total mortalities (Z) calculated by non-seasonalized length-converted catch curves were 0.83 year-1. Catch curve is shown in Figure 8. Natural mortality was estimated as M= 0.69 year-1 (annual mean water temperature was evaluated






as 19.5 oC). Fishing mortality coefficient F was 0.14 year-1. E (exploitation rate) was computed as 0.17. Annual survival rate was estimated as 43.60%, 9.52% and 46.88% for S (survive), C (fishing), D (natural), respectively.

Using the Knife-Edge selection procedure for the analysis of relative yield and biomass per recruit of O. mykiss (Fig. 9) gave an Emax, (the value of exploitation rate E giving the maximum relative yield per recruit) of 0.618, E0.1 (the value of E at which increase in the Yˈ/R is 10% of its value) of 0.520 and E0.5 (the value of E at 50% of the unexploited relative biomass per recruit) of 0.327 (Table II). Selection ogive procedure of O. mykiss is shown in Figure 9. E0.1, E0.5 and Emax values estimated as 0.517, 0.316 and 0.618, respectively, based on ogive procedure.






The reason for low or no fish catch during June, July and August is because of high water temperature. The decrease in water depth may also be cause of sudden rise of water temperature which makes the fish to move to deeper lake area or relatively colder spring waters supporting the Dam Lake.

In this study, O. mykiss population of Karacaören-I Dam Lake’s showed positive allometric growth proportion (b>3). This result showed parallelism with other studies which were conducted in Turkey (i.e. Erguden and Goksu, 2009; Çiçek and Birecikligil, 2013). But our b value was different from the one reported by Leiner (1995),


Table II.- Result of Relative Yield/Recruit Analysis for O. mykiss (Lc/L=0.380; M/K=2.09).

Parameters Knife edge selection Ogive selection


0.520 0.517


0.327 0.316





Table III.- Summary of previous biology studies on O. mykiss.



Location Author
N a b


Length-weight relationship

157 -4.698* 2.88 0.96 Rio Gr.,Str, New Mexico Leiner (1995)
16 -4.377* 2.73 0.94 Red Stream, New Mexico
8 -5.687* 3.30 0.98 Pecoz Stream,New Mexico
39 0.004 3.29 0.92 Seyhan Dam Lake, Turkey Erguden and Goksu (2009)
794 0.00005 2.69 0.98 Lemme Creek, Italy Candiotto et al. (2011)
359 -4.921* 2.96 0.99 Dachigam Stream, India Shah et al. (2011)
87 0.0066 3.19 0.99 Ecemiş Stream, Turkey Çiçek and Birecikligil (2013)


3.39 0.86 Kashmir Valley, India Sharma and Bhat (2015)
166 0.006 3.20 0.96 Karacaören-I D.L. Turkey Present Study
Condition factor








Flaming Gorge, USA Budy et al. (2003)




Dachigam Stream, India Shah et al. (2011)




Kashmir Valley, India

Sharma and Bhat (2015)





Karacaören-I D.L. Turkey Present Study








Mimbres Str., New Mexico Leiner (1995)




Red Stream, New Mexico




Sacramento River, USA Glowacki (2003)




Kadıncık Stream, Turkey Korkmaz (2004)




Lemme Creek, Italy Candiotto et al. (2011)




Karakaya D.L. Turkey Ateşşahin et al. (2011)




Karacaören-I D.L. Turkey Present Study

Growth parameters








Mimbres Str., New Mexico Leiner (1995)




Red Stream, New Mexico




Karacaören-I D.L. Turkey Present Study
Mortality rate










Mimbres Str., New Mexico Leiner (1995)





Red Stream, New Mexico





Karacaören-I D.L. Turkey

Present Study



Candiotto et al. (2011) and Shah et al. (2011) (Table III). The mean condition factor estimated as 1.13 is similar to that reported by Shah et al. (2011) but very low compared to 1.83 reported by Sharma and Bhat (2015). It is thought that this differences may be due to sex ratio distributions, feeding status, age distributions, number of samples and sampling period.

While estimated K value (0.33) is similar to (0.39) that reported by Leiner (1995) for Red stream O. mykiss population, it is different from that of Mimbers stream population (0.08) reported by same author. It is assumed that this difference is because of different number of samples, sampling methods (i.e. gillnet vs electro shockers) and origin of rainbow trout. Davis (2012) reported that wild fish exhibited faster growth than the rainbow trout raised in a hatchery and he developed a non-lethal method to differentiate between hatchery-raised and naturally reproduced rainbow trout based on growth characteristics of scales.

It could not be explicitly determined that whether recruitment of O. mykiss in Karacaören I Dam Lake was based on self-sustaining individuals or due to escape from the nearby aquaculture facility every year. Davis (2012) reported that managers should focus on continuing to monitor genetic contribution to natural reproduction by hatchery-reared rainbow trout and also fisheries biologists should focus on continuing to improve non-lethal technique to continue to monitor recruitment.

In the light of relative yield and biomass recruit information, it can be concluded that there are no serious fishing pressures on stock, since the estimated Emax with knife-edge selection (0.618) and ogive selection (0.618) greater than current exploitation rate (E = 0.17). The main target of fishermen are common carp (Cyprinus carpio) and Prussian carp (Carassius gibelio) in Dam Lake, so fishermen use gillnet and trammel nets with 100-110 mm stretched mesh size intended for this species. These nets are very inefficient in O. mykiss fishing due to very large size of this species. Estimated fishing mortality (F=0.14) may originate from pikeperch’s (Sander lucioperca) nets or tangling with teeth on carps nets. The anglers probably cause least fish mortality.




It shows that O. mykiss stock is not use within economic ratability scope due to most of the deaths based on natural. Because of gillnets are inefficient in O. mykiss fishing (Cilbiz et al., 2015), angling may be encourage in Karacaören I Dam Lake for better exploiting of the O.mykiss stock.




This study founded by Republic of Turkey, Ministry of Food Agriculture and Live Stock with TAGEM/HAYSUD/2013/A11/P-02/7 project number.


Conflict of interest statement

We declare that we have no conflict of interest.




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