Fish assemblages as influenced by environmental factors in Taleghan River (the Caspian Sea basin, Alborz Province, Iran)

[Research]

Fish assemblages as influenced by environmental factors in Taleghan River (the Caspian Sea basin, Alborz Province, Iran)

M. Zamani Faradonbe, S. Eagderi*

Fisheries Department, Faculty of Natural Resources, University of Tehran, Karaj, Iran.

* Corresponding author’s E-mail: soheil.eagderi@ut.ac.ir 

ABSTRACT

The relationship between some habitat factors and fish assemblage was analyzed in the Taleghan River, Alborz Province, Iran. Fish specimens from thirty-three sites were sampled by electrofishing device in October 2014. The habitat parameters, including elevation (m), water depth (cm), river width (m), river slope (%), current velocity (m.s^-1), number of large stone (> 15 cm), average stone diameter (cm), substrate index (SI%), level of potamal cover, level of periphyton cover, pH, electrical conductivity, total dissolved solid and temperature (°C) were measured in all sampling sites. Canonical correspondence analysis was performed to study the relationship between fish assemblage and environmental factors. The results showed that the fish assemblages of the Taleghan River are organized by the environmental variables. Based on the results, the abundance of C. gracilis did not show any distinctive relationship with examined habitat variables, whereas the presence and abundance of B. cyri showed a rise with increasing substrate index and bed stone diameter and a decline with increasing river width and flow velocity. The presence and abundance of O. bergianus rises with the increasing current velocity and river width and showed a decline with increasing slope, depth and substrate index. The results of this study provides insights into the ecology of fishes in the Taleghan River and can help an effective fisheries management of other rivers of the Caspian Sea basin.

INTRODUCTION

The relationship between habitat parameters and fish assemblage is one of the main themes in aquatic ecology (Angermeier & Davideanu, 2004). The structure of fish assemblages is generally dependent on many biotic (e.g. habitat biodiversity, dispersal, competition, and predation) and abiotic (e.g. pH, alkalinity, DO, elevation, stream size, depth, and climate) factors (Ricklefs, 1987; Jackson & Harvey, 1989; Persson, 1997; Brown, 2000; Angermeier & Davideanu, 2004). These factors can also act independently and constrain the presence and distribution of stream fishes through a hierarchy of nested environmental filters. In addition, the features of fish assemblages in riverine ecosystems are dependent on the interaction of multiple ecological processes over changing temporal and spatial scales

(Poff, 1997). Furthermore, the anthropological activities can affect riverine ecosystems (Cowx & Gerdeaux, 2004; Van Zyll de Jong et al., 2004) by changing the biotic and abiotic factors (Jennings et al., 1999).

The relationships between abundance and distribution patterns of fish assemblage and environmental factors that are responsible for their organization, is essential for understanding the community dynamics and predicting how external (e.g. introduction of exotics) and internal (e.g. eutrophication) mechanisms could influence fish assemblage structure (Robinson & Tonn, 1989). In addition, understanding the temporal and spatial changes in fish assemblage can be useful as a basis for management of stream fisheries (Van zyll de jong et al., 2004).

Since, there is no information available about the spatial and temporal patterns of fish assemblage and its relationship with environmental factors in any river of the Caspian Sea basin with 119 confirmed species (Esmaeili et al., 2010); hence, this study was carried out to describe the relationship between several habitat characteristics and fish assemblage in the Taleghan River (a river in the Caspian Sea basin, Iran) to address the important and effective environmental factors on its fish assemblage using presence-absence and abundance data of fishes and measuring environmental factors in situ influences the variability of fish assemblage.

MATERIALS AND METHODS

Sampling

Thirty-three sampling sites distributed in elevation profiles were selected to cover all available habitats along the Taleghan River (Fig 1). Fish were collected by a backpack electrofishing device (Samus Mp750, 45 cm diameter, aluminium ring anode) and using upstream and downstream stop-nets with 0.2 cm mesh size in October 2014. For sampling, one-removal method with similar catch-per-unit effort strategy was employed (Klaar et al., 2004). The fished sections were minimally 100 m long. All collected fish belonging to three species (Error! Reference source not found.) were returned to the river after identification and counting.

Habitat Data

The habitat data were measured immediately after sampling. The measured variables include (m), river slope (%), current velocity (m.s^-1), number of large stone (>25 cm), average stone diameter (cm), substrate index (SI%), Potamal Cover Index (PoCI), Periphyton Cover Index (PeCI), pH, electrical conductivity (EC) (µs), Total Dissolved Solid (TDS) (ppm), and temperature (°C). Elevation and geographical coordinates of the sampling sites were recorded by GPS (Global Positioning System; Garmin). Stream depth (cm) was measured at 20 points across sampling site using a measuring bar, and their average was considered as river depth (Lotfi, 2012). Width of river was measured using a tapeline by measuring anterior, middle and end of each sampling site and their average was considered as river width. River’s slope (%) was measured by Sunto. Current velocity (m.s^-1) was measured by a simple float based on Hassan-lie (1999).  Using Lotfi (2012) as the basis, the following measurements were carried out:  number of large stones (> 25 cm) were calculated by counting large stone in 20 selected quadrates (50 × 50 cm), and stone diameter average also were calculated by measuring diameter of the bed stones in 20 selected quadrated (50 × 50 cm).   Substrate index (SI) was calculated using the following formula: SI= (0.08 × area of bedrock) + (0.07 × area of boulder) + (0.06 × area of cobble) + (0.05 × area of gravel) + (0.035 × area of fines) (Jowett et al., 2008). The potamal cover index and periphyton cover index were determined visually in site as percent of surface according to Platts et al. (1983) and Schultz et al. (2012).  Finally, pH, EC and TDS were measured using a portable water quality instrument (WTW GmbH).

Fig.1. Map of sampling sites in the Taleghan River.

Table 1. The list of collected fish species, their scientific and English names.

Statistical Analysis

The direct gradient Canonical Correspondence Analysis (CCA) was applied to discover the relationship between fish assemblage and habitat factors. This method is a direct gradient ordination technique for describing the major trends in species distribution and correlated environmental factors. Initially, all habitat variables were included in the CCA. In addition, the variance inflation factor (VIF) was used to assess independence of included variables in the CCA. VIFs greater than 20 indicate correlation among variables (ter Braak & Verdonschot, 1995); nevertheless, the variables with VIFs more than 5 were removed from the CCA in this study. Other variables were removed from the post-hoc analysis if they did not explain variation along major axes in an easily interpretable way (Jongman at el., 1995; ter Braak & Verdonschot, 1995).

The final CCA was used for explanation of fish assemblage-habitat factors relationship. An ordination biplot containing species and environmental variables was applied to extract the relationship between habitat factors and individual fishes of assemblage. The species abundance-environmental variables biplot is an ordination diagram in which species represented as points with respect to the explanatory variables represented as vectors. The vectors show the direction of maximum variation of the corresponding variable (ter Braak & Verdonschot, 1995).

RESULTS

Three species were included in the final CCA (Table 1). The variables in the final CCA were water depth (cm), river width (m), river slope (%), current velocity (cm/s), number of large stone (> 25 cm), average stone diameter (cm), substrate index (SI%), pH, EC (us), and TDS (ppm). The included variables in the final CCA were not redundant (r < 0.60); the removed variables with VIFs > 20 were elevation, temperature, PoCI, and PeCI. The relationships of ten habitat variables and structures of fish assemblage were depicted in Figures 2 & 3. The position of a species relative to a vector of environmental variables indicates how a species is associated with the environmental variables (Figs. 2 & 3).

Presence-absence data

The first two axes of CCA explained 93.067% and 6.933% (100% in total) of the variation in fish assemblages, respectively. The eigenvalues, which range between 0 and 1, show the importance of each axis. The eigenvalues of axis 1 and 2 were 0.157 and 0.134, respectively. River width (0.50) and slope (-0.81) were highly correlated with the first ordination axis and have stronger gradients than the other variables. Total dissolved solid (TDS) (-0.63) was the most correlated parameter with the second axis (Table 2).

The biplot generated for presence-absence data explained that (1) presence-absence of O. bergianus (Oxbe) is positively associated with current velocity and river width and negatively with pH, slope, depth and average of stone diameter; (2) presence-absence of B. cyri (Baci) is positively associated with substrate index and average of stone diameter, and negatively related with current velocity, river width,  EC and TDS; (3) Presence-absence of C. gracilis (Cage) individuals are positively associated with slope, depth and number of large stone (Fig. 2).

Abundance data

The statistical significance of the CCA ordination was confirmed (P < 0.0001). The first two axes explained 97.480 % and 2.520 % of the variation in fish assemblages, and the eigenvalues of axis 1 and 2 accounted as 0.380 and 0.010, respectively.

The flow velocity (-0.59) as negative and slope (0.61) as positive, were the two highly correlated factors with first ordination axis (Table 3). These factors represent the most important environmental factors related to the structure of fish assemblages. River width (-0.55) and number of large stone (-0.61) were negative and highly correlated with the second ordination axis (Table 3).

Table 2. Inter-set correlations of significant (P < 0.05) environmental variables with the first two ordination axes of the final CCA (presence-absence data).

Table 3. Inter-set correlations of significant (P < 0.05) environmental factors with the first two ordination axes of CCA (abundance data).

Fig. 2. CCA ordination diagram showing the effect of significant (P < 0.05) environmental factors on the structure of fish assemblages (presence–absence data).

The biplot obtained from abundance data revealed that (1) abundance of O. bergianus (Oxbe) is positively associated with current velocity and TDS and negatively with pH, substrate index and slope; (2) abundance of B. cyri (Baci) is positively associated with pH, substrate index and negatively with river width and EC; and (3) abundance of C. gracilis (Cage) has not distinctive relationship with any habitat variables (Fig. 3).

Fig. 3. CCA ordination diagram showing the effect of significant (P< 0.05) environmental factors on the structure of fish assemblages (abundance data).