INTRODUCTION:

The aquatic ecosystem structurally comprised of biotic and abiotic components. The abiotic components include physico-chemical characteristics of water and soil and also the climatic conditions. The combined effect of high temperature and minimum flow is deleterious to aquatic organisms with reduction in the dissolved oxygen quantity. There are also seasonal water variables with intense rainfall events as drainage of nutrients from bottom and sides to the floodplains. The community homogenization in endemic or exotic species is also expected (1). The spawning behavior of fishes might be triggered due to combined experiences imposed by increased heat and water volume in the small ponds. These variables are also important in regulating seasonal alterations in existing populations (2).

The ponds are dynamic, highly productive lentic water bodies with rich biodiversity. The fish pond ecology is a primary evidence for their higher productivity (3). The ponds are as important freshwater ecosystem with diversified fauna and flora (4). The tropic ponds are even increasing potential as habitat of fishes and several methods encompasses entry of exotic variety, adoption of culture techniques and ecological management skills to enhancing fish production (5).

Fishes are primarily aquatic vertebrates. Fishes are nekton of the aquatic system. They are the chief component of aquatic productivity. Fishes are heterotrophic and are secondary/ tertiary producer as well as consumer of the aquatic system. Fishes are adapted to its environment. The environmental alteration limits species interaction between fishes. A species is characterized by a relative morpho-physiologo-ecological stability, which is the result of adaptation to a particular environment under the condition of which the species was formed and with which the species in the unity (6). Fish being rich in proteins, can supplement the protein deficient diet of the people. Fisheries occupy an important position in the economy of the state or country.

The ponds need to improve through suitable management for fish productivity as modern aspect (7). There pond management is needful with modern concepts about its population structure to protect existing organisms (8). In India, several studies have been made to understand the physicochemical properties of lakes, reservoirs and ponds (9-11). The ponds have to be identified and distinguished from other ecosystem by their ecological characteristics alone. To ensure management and conservation of pond resources, the ecological studies about the ecosystem components are most essential which provide a baseline data regarding sustainable management measures of a particular pond ecosystem. The ecological studies of ponds will help to derive material benefits from the environment on sustained basis without destroying it.

METHODS AND MATERIALS:

In the present study, the fish diversity in the floodplain wetlands was examined by using two methods - (i) through spot verification of fish catch during the harvesting seasons and (ii) fish species reported by the fishermen in the questionnaire. Fish catch composition and fish species diversity had been collected by spot verification during physical survey at the fish landing stations. Only for those fish species which could not be recorded during physical survey were recorded from questionnaire. In the first method the fish species were indentified on the spot during fish landing in the fish landing stations. The species which could not be identified on the spot were brought to the laboratory and these were identified by using different keys of various standard literatures. The fish diversity was calculated as-

Diversity index H̕ (12) was estimated following the formulae-

Shannon-Wiener index: H̕ = -Σ pi In pi

Pi = n/N, n = diversity of individual and N = total density

To determine the composition of fish, the fish species were classified into three categories based on size ranges - (i) major group, (ii) intermediate group and (iii) minor group. Major group fish is composed of fish species with the size above the size of juveniles and are generally the large growing fishes. On the other hand, the intermediate group includes the sizes equivalent to or less than the size of juveniles of Indian Major Carp (IMC), and minor group fish includes all fish species with a size equivalent to or less than the fingerlings of IMC. The fishermen while selling their catch in the auction center commonly follow this categorization. This principle/definition was, however, not being applied while analyzing the fish diversity in the wetlands.

For the analysis of fish diversity, the classification into three groups was based on the size consideration at the maturity stage. For instance, the juveniles of IMC are considered under intermediate group for determination of fish biomass composition, whereas the same was considered under major group for analysis of fish diversity. Similarly, the fingerlings of IMC were considered under minor group in terms of biomass composition, and under major group for analysis of fish diversity.

The fish biomass composition of each category was observed on the spot at the time of fish selling in the auction center (fish landing center). The second method was also adopted simultaneously to know more about fish biomass composition of the individual wetlands. In the second method, individual fishermen were asked to indicate the total fish biomass production of individual group and also the fish species available in the wetland. The final composition of fish in terms of weight was determined by taking the aggregate of data procured from spot observation and report from local fishermen.

The collections of small- sized fishes were made with the help of a “Bag net" which is like a butterfly net strongly built with thick mesh and long handle. Details of other types of nets and tackles will be discussed in the Fish productivity chapter. They were preserved in 10 % formalin and brought to the laboratory for identification. The identification of fishes were made with the help of available literature of Jhingran (13), Jayaram (14) and Talwar and Jhingran (15).

RESULTS AND OBSERVATIONS:

The Ponds have rich diversity of fishes during study period, however, fish production in recent years dramatically declined as a result of anthropogenic disturbances in wetland area. The community characteristics presented in Table 1.

Table 1: Fish assemblage in Ponds wetland during study period

Family	Genus	Pond 1	Pond `2	Richness	Abundane
Cyprinidae	Catla	12	13	3	34
	Labeo	7	7	4	26
	Mystus	7	-	2	6
	Puntius	3	3	2	11
Bagridae	Mystus	-	-	1	4
Siluridae	Ompok	-	-	2	7
Mastacembelus	Mastacambelus	8	4	3	27
Notopteridae	Notopterous	10	10	3	25

The survey of ponds revealed differences in fish catches of the experimental ponds during the research period. It is more or less correlated with anthropogenic disturbances as Pond 1 has excessively encroached for agricultural practices and also domestic drainage is higher than Pond 2. This difference also altered chemical variables at both ponds which also affecting fish catches in these ponds as analyzed (Table 2 and Table 3).

Table 2: Monthly fish group catches at Pond 1 in study period

Group	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Major carp	73	104	113	213	134	248	82	41	30	28	27	21
Local carp	64	82	87	132	43	41	19	17	15	13	14	12
Miscellaneous	16	23	38	40	44	23	13	19	17	16	15	11
Total	153	211	238	385	221	312	124	77	62	57	66	44

Table 3: Monthly fish group catches at Pond 2 in study period

Group	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Major carp	86	117	123	174	137	187	72	37	29	21	19	17
Local carp	73	96	93	153	52	47	36	21	23	20	18	20
Miscellaneous	19	25	47	39	56	31	21	19	21	18	15	16
Total	178	241	263	366	245	265	129	77	73	59	52	53

The seasonal variation in fish catches are presented in Figure 1 and Figure 2. This analysis showed maximum catches in summer and minimum in winter season. It is also clear that more abundant group is major carp followed by local carp and miscellaneous fishes.

Figure 1: Seasonal fish catches at pond 1 of Saran district

Figure 2: Seasonal fish catches at pond 2 of Saran district

The month wise catch analysis revealed maximum in April and June and minimum in November and December for Major carp, maximum in April and minimum in November for Local carp, while maximum in March and April and minimum in November for miscellaneous fishes (Figure 1 and Figure 2). The Major carps are abundant at pond 1, Local carp and miscellaneous fishes at pond 2 respectively (Figure 3, 4 and 5).

Figure 3: Monthly Major carp catches at ponds of Saran district

Figure 4: Monthly Local carp catches at ponds of Saran district

The fish catches in experimental ponds are verified with local fishermen and survey method to know about monthly catches in the ponds. The fish catches may be some deviation from original biomass of these fish guilds as some fishes were not caught in harvesting of pond during the experimental period of study.

Figure 5: Monthly Miscellaneous catches at ponds of Saran district

DISCUSSION:

Forty seven species at pond 1 and thirty seven species existed at pond 2 of Saran district showed rich fish diversity. The rich fish diversity in the ponds has been reported by a number of previous workers (16-17) from their studies in a limited number of water resources.

The breeding habitat is also one of the important parameter from the point of view of fish diversity. The breeding environment of the ponds has been observed to be conducive in most of the lentic ecosystems. The surrounding physiographic conditions of the ponds create an environment for the fish species to breed in the ponds. The brooders generally prefer the shallow catchment areas provided with grasses, submerged or emergent macrophytes and shallow paddy fields. A similar finding was also put forward by Sugunon and Sinha (18) who reported that fishes find their shelter and food in the littoral plants of lake or in emergent marshes. He also opined that several fish species move into marshes from adjacent lakes to breed and some fish species also use marshes as their nursery ground/habitat.

Five number of Indian Major Carp (IMC) species namely L.rohita, L. calbasu, L. gonius, Catla catla and Cirrhinus mrigala are found significantly in both of the ponds. The existence of these fish resources in the wetlands of Assam also reported in the previous studies. The ponds of Bihar provide the fishes with favorable breeding environment because of which IMC species are still continuing their life in the ponds in spite of several constraints (17).

Emergence of exotic carps is a significant event in the context of fish diversity in the ponds of Bihar. Their presence in the ponds was not reported in the study made before 1987. In contrast, the present study identifies three number of exotic carps species namely Hypophthalmichthys molitrix, Ctenopharyngodon idella, and Cyprinus carpio in these ponds. Presently, the populations of these species are not high and have not reached an alarming position. However, if population of these species increase in the future, they will compete with the indigenous species as a result they are likely to suffer and may lose their population. This fact is quite evident from the study of Goswami, (19) and Chakraborty (20) which ascertained that decline of fish diversity has also been aggravated by the introduction of exotic species which are damaging the indigenous carp and other fish species through competition for food and space in the local ponds. Though in Bihar, the competition between exotic and indigenous carp species in the ponds is not yet significant, the newly introduced cat fish species Clariaus garipenius (Thai magur) may intensify the competition for food in some ponds of Bihar. Unless this exotic catfish species is prevented from its emergence into the ponds, a large number of minor and intermediate group fish species may disappear from the ponds.

The catch composition of major, intermediate and minor group fish species varies from pond to pond depending on topography of the basin as well as zoogeographic situation of the fish species. The present status of the fish composition in the ponds indicates that the minor variety fish population dominates over the major and intermediate (minor>major>intermediate) variety fish population. But it is reported by the fishermen that major variety fish population in terms of weight was higher than the intermediate and minor variety fish population in the long past. The present reversal trend in catch composition convincingly establishes the high yielding habitat condition of the ponds for the major group. The major group is suffering due to indiscriminate fishing of brooders during breeding season, killing of fry and fingerling, destruction of eggs and spawn, and use of Musari jal (an encircling net) of 1.0 to 3.0 mm mesh size. This finding is in conformity with the findings of Jha (21).

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Received on 27.02.2023 Modified on 05.03.2023

Research J. Science and Tech. 2023; 15(1):35-40.

DOI: 10.52711/2349-2988.2023.00007