Fisheries and Aquaculture Journal

Composition, distribution and abundance of fish species was carried out from April 2012 to Mars 2013 in the Shadegan wetland. Samples were collected from five stations; Mahshar, Rogbe, Khorosy, Salmane and Ateish in this local in Khuzestan provinces (Iran). A total of 3312 fish individuals comprising 26 species from 6 families were sampled throughout the entire study period. The most abundant species was Carasobarbus luteus (Cyprinidae) comprising 28.20% of the total fish caught. The mean CPUE (catch per unit effort) for all species was 29 nu/day and maximum and minimum CPUE values were 47.60 ± 11.61 nu /day (spring) and 18.40 ± 5.94 nu /day (winter), respectively. Maximum and minimum Shannon-Weinner values were 2.21 (spring) and 2 (autumn), respectively. The Shannon-Weinner value differ significantly between different station (P<0.05) and Margalef’s, Evenness, Simpson’s index didn’t differ significantly between different station (P>0.05). A comparison of value salinity is significant between different station (P<0.05) and other parameters is no significant different station (P<0.05). The Wetland Fish Index (WFI) calculated for the entire wetland using total abundance was 2.99. The WFI should prove to be an effective tool to aid in the management and protection of important fish habitat in Shadegan wetlands.


Introduction
It is important to know the fish species diversity, abundance and distribution in the reservoirs in order to develop management and conservation programs. Studies of spatial and temporal patterns of diversity, distribution and species composition of freshwater fishes are useful to examine factors influencing the structure of the fish community [1]. Biodiversity is the quantity, variety and distribution across biological scales ranging through genetics and life forms of populations, species, communities and ecosystems [2]. Biodiversity is important for the future sustainability of natural resources that include commercial fisheries. While it is axiomatic that biodiversity is essential for sustainable productive fisheries there is surprisingly little supporting evidence. Fish species are also an important indicator of ecological health. The abundance and health of fish will show the health of water bodies [3]. This is supported by Zainudin [4] who claimed that fish species diversity can be used as a biological indicator to show the level of aquatic pollution contributing to environmental quality. Biodiversity affects the capacity of living systems to respond to changes in the environment, underpins ecosystem function and provides the ecosystem goods and services that support human well-being [5,6]. This has led to the development of some management programs to conserve and to increase needs for the freshwater fish population.
Wetlands are invaluable ecological resources that serve many human needs and therefore, enhance our lives by providing a lot of opportunities. Many depend heavily on the resources of such water bodies as their main source of animal protein and family income [7]. Wetlands in the world was included about 7 to 9 million km 2 (4-6 percent of Earth surface). Iran wetlands are approximately 1853762 ha and between Middle East wetland was contained 25% [8]. Shadegan Wetland in Khuzestan province is one of the 18 international wetlands registered on UNESCO's Natural Heritage List. Located 52 km from Abadan and 105 km from Ahvaz, it is Iran's largest wetland and by Linking Jarahi River connect with Persian Gulf waters, the wetland is considered one of the most wonderful natural landscape of the world because of it is unique biodiversity [9]. In 2006, fish landings in Shadegan wetland reached a peak of 3700 tons, which corresponds to more than 10 billion$ [10]. The wetland is a unique natural asset for the province of Khuzestan, supporting a rich biodiversity, including threatened and endemic species. water resources development for agricultural intensification in the upstream catchment which would reduce the volume of the inflows, and change the seasonality of flooding development of heavy industries and infrastructures around and within the wetland pollution from industrial, urban and agricultural (including aquaculture) wastes oil spills [9].
In this study, we examined the fish species composition, distribution and abundance in shadegan wetland. Our main aims were to: (i) Estimation of fish species composition, distribution and abundance, (ii) different distribution and abundance in stations and seasons. Maramazi [11], Ansari and Mohamadi [12,13] and Ansari et al., Hashemi et al., were searched fish survey, stock assessment and capture conditions of shadegan wetland. Lotfi et al., [9] were considered human activity and effect on shadegan wetland and also diversity and capture situation of shadegan wetland. However, one study so far has been made on fish distribution and abundance in shadegan wetland. For rational and sustainable management of this exploited resource, information on the species composition, abundance, distribution, and growth are provided. These data can be used to better fisheries stock management for these valuable fish.

Study area
Composition, distribution and abundance of fish species was carried out from April 2012 to Mars 2013 in the Shadegan wetland. Samples were collected from five stations; Mahshar (48˚,45´ E,30˚,33´ N ), Rogbe (48˚,33´ E, 30˚,41´ N ), Khorosy (48˚,40´ E, 30˚,39´ N ), Salmane (48˚,28´ E, 30˚,40´ N ) and Ateish (48˚,40´ E, 30˚,54´ N ) in the Shadegan wetland in Khuzestan provinces ( Figure 1). In each month, 5 stations were selected for sampling. Fish species was carried out by using gill net with 45 mm mesh and then Sampling transported to lab with dry ice. The gill nets were set at dusk and hauled the next morning. All fish caught were identified to species using standard taxonomic keys following Nelson and Coad [14,15].

Data collection
Habitat monitoring and fish sampling were carried out seasonally from September 2012 to September 2013. Fishing gears set for sampling at study sites were sometimes destroyed by other fisherman in this wetland. In such cases, data collection was repeated in the next year at the same place and the same time period. Sampling started at a random point and then proceeded at evenly distributed intervals along the shoreline of the water body. Seasonally water samples for analysis of environmental parameters were collected from each station using a Nansen bottle sampler and analyses as per standard analytical procedures [16]. Eighteen environmental parameters (Table 1) were considered in this research and included water temperature (WT), water depth (WD), water salinity (WS) phosphorus (TP), nitrate (TN), PH, biological oxygen demand (BOD) and dissolved oxygen (DO).

Diversity of fish species
The diversity of fish species was estimated in terms of species evenness, using Margalef's D index, Shannon Wiener, Evenness

Wetland fish index (WFI)
To develop the WFI, each species was assigned U and T values according to the following equation [19].

YiTiUi WFI YiTi
Where Yi is the presence or log10 abundance (log[x + 1]) of species i, Ti is the value from one to three (indicating niche breadth), and Ui is the value from one to five (indicating tolerance of degradation). CANOCO 4.5 [19] was used to run canonical correspondence analysis (CCA) as in Seilheimer and Chow-Fraser [19,20]. Canonical correspondence analysis (CCA) was used to explore the distribution of the fish communities in relation to the environmental variables. If a species occurred only once, it was excluded from the CCA analysis. Environmental variables selected for the CCA analysis included continuous variables, such as water quality data (e.g., pH and COD). All continuous environmental variables were log (1 + x) transformed and standardized to have a zero mean and unit variance. Comparison of environmental parameters and species diversity, abundance, richness during different spatial and temporal carried out by analysis of variance (ANOVA). Statistical analyses were performed with SPSS 21 software package and a significance level of 0.05 was adopted.

Result
A total of 3312 fish individuals comprising 26 species from 6 families were sampled from Shadegan wetland throughout the entire study period ( Table 1). The most abundant species was Carasobarbus luteus (Cyprinidae) comprising 28.20% of the total fish caught, followed ratio and Simpson's. Species diversity, abundance and richness are determined by following May (1993)  In order to test for differences in diversity among fishes in different seasons of the year, pair wise randomization tests were carried out, abundance data following May (1993). The analyses were performed as per the method of May [18] using Species Diversity and Richness software and Microsoft Excel sheet.   Figure  2).

CPUE (catch per unit effort)
The mean CPUE (catch per unit effort) for all species was 29 nu/ day and maximum and minimum CPUE values were 47.60 ± 11.61 nu /day (spring) and 18.40 ± 5.94 nu /day (winter), respectively. The mean depth of fishing was 1 m and ranged from 0.5 m to 2.5 m. Value CPUE in each Station ( Figure 3) and this value in different season was showed (Figure 4). A comparison of value CPUE is significant between different season (ANOVA, F=16.09, P<0.05) and there is significant different station them (ANOVA, F=73.49, P<0.05).

Environmental parameters and diversity of fish species
Physic-chemical parameters and diversity of fish species are shown in Tables 2-4

WFI and CCA
The WFI calculated for the entire wetland using total abundance was 2.99. These values fell between a possible range of 1-5, where 1 is most degraded and 5 is least degraded. An ordination of the 26 fish species with eight environmental variables produced significant correlations between species and variables associated with environmental degradation for AB data ( Table 1). The position of a species on the CCA biplot is a reflection of the environmental conditions where it was found. The first axis of the CCA was strongly correlated with environmental conditions, where the positive end of CCA axis 1 was associated with species normally found in degraded conditions (e.g.,    Figure 5).

Discussion
The native marshland fish populations were originally dominated by Cyprinid fish of the genus Barbus. Hashemi et al. [21] reported that C. carpio was the most abundant species in their study in shadegan wetland. Overall, B. luteus, M. sharpeyii, C. carpio, C. carasus, A. vorax and L. abu are included over 70% biomass and fish main species of Shadegan wetland species [21]. The dominance of cyprinids in tropical reservoirs has been observed in Sri Lankan reservoirs, where the family formed over 50% of the species present [22]. Abundance of fish populations in river, lake with river source and reservoirs widely changed from year to year and the relative frequency of different species is different in population. This change is affected by rainfall fluctuation and floods. The increasing area and flood flow time is improved spawning, growth and survived rate [23]. Bias associated with fishing gear types can greatly influence comparisons of aquatic habitats, especially when meaningful community information is desired for habitat restoration research [24].
The east stations in different seasons have high amount of Shannon-Weinner. It seems that entering the Jarahi River for east side of the wetland and entering of nutrition element was the reason of phytoplankton increasing and phytobentoz production [25] that caused Shannon-Weinner values increase in these areas. The south station have high amount of Shannon-Weinner that caused entering marine fish species in different seasons to wetland (especial summer and autumn seasons [13]. Six species of Cyprinidae (C. carpio, H. molitrix, H. nobilis, C. idella, B, grypus, M. sharpeyii) were introduced to Shadegan wetland in 2009 to 2012 by the Department of Fisheries Iranian as a potential for fishing in this wetland. This was done under one of the regulation and conservation programs towards maintaining and enhancing the fishery resources in this local. It seems, with induces six species of Cyprinid, abundance fish has increased. This clearly showed that the species diversity indices values using Shannon-     Table 1 for species numbers) from canonical Correspondence analysis (CCA) with 8 environmental variables in shadegan wetland. The maximum CPUE obtained was in spring (inversely in Autumn season), it seems related to wetland climate status [13] and nutrients entering to river flow may be due to the season and also maximum phytoplankton production, wetland phytobentoz which was showed in spring time [25]. Managers commonly use catch per unit of effort (CPUE) methods for estimating population size and catchability coefficients in fish fisheries, because these parameters are key in the exploitation [27].
WFI scores was reported 2.64 in Shadegan wetland that near our finding (WFI=2.99). Interannual variation in WFI scores was not large and implies that the index will be a powerful tool for monitoring and for comparing scores calculated for wetlands sampled in different years. Fish are a suitable group of organisms for monitoring aquatic condition because they have a documented relationship with environmental perturbations (i.e., increased trophic status and degraded fish community). Variation in environmental condition cause changes in the fish community and those changes can then be extracted into ecological indicators to quantify environmental impacts [19]. For best results, we recommend consistent sampling gear and fishing effort be used when collecting fish data for use with the WFI. When WFI compared with other diversity indices (Shannon-Wiener's H′, Simpson's, evenness, and species richness), only the WFI varied as a linear function of WQI (Water Quality Index), demonstrating that the WFI is more useful than the others as an indicator of anthropogenic impact [20].
In the CCA ordination, axes 1 and 2 together explained a high percentage of variance of the species-environment biplot, with temperature, salinity, NO 3 and PO 4 , as the most important variables influencing the variation of fish composition in the Shadegan wetland ( Figure 5). It seems in multivariate indices; Do and BOD have low affect associated with species distribution. Thus, the fish assemblage of the freshwater-influenced habitat was characterized by the presence of numerous species that are tolerant to low-salinity conditions, and enter the system mainly for food and protection. The fish assemblage of the marine-influenced habitat was characterized by the presence of occasional and seasonal species. Multimetric indicators are especially vulnerable to bias because many of the metrics use community factors, such as percent of total catch from feeding guilds or percent of total biomass from specific species [28].
Finally, Fish are only one of many bioindicators in use today, but it is only a single tool and should be used in accord with other indices for greatest knowledge of wetland condition. Nevertheless, the Wetland Fish Index should prove to be an effective tool to aid in the management and protection of important fish habitat in Shadegan wetlands. This study provides basic information for fishery biologists in this local [29][30][31][32][33][34][35].