Utilisation of water hyacinth (Eichhornia crassipes) as fish aggregating device by riverine fisher folks in a South West Nigeria community

Olorunwa Eric Omofunmi¹, Adesoji Matthew Olaniyan¹ and Olubukunola Tony Ebietomiye²

¹ Department of Agricultural and Bioresources Engineering, Faculty of Engineering, Federal University, Oye-Ekiti, P. M. B. 373, Oye-Ekiti 371101, Ekiti State, Nigeria
omofunmieric@yahoo.com
² Department of Fisheries and Marine Technology, Federal College of Fisheries and Marine Technology, Victoria Island, Lagos, Nigeria

Abstract

Water hyacinth (Eichhornia crassipes) despite its acclaimed ``high nuisance value``, prove having immense economic value to the fisher folks in the riverine areas of Ondo State, Southwest, Nigeria when used as passive Fish Aggregating Device (FAD) Extensive Culture Receptacles, in a two-year study. The WH-FAD; WH, denoting Water hyacinth, isolated 0.18 ha of rivulets and creeks of appreciable salinity level (5%). Fish population estimate obtained was, 2,200 WH_FAD^-1. This figure fell within the range of calculated values, P (1,939 ) = 0.95 that amounted to a yield of 3.7 tons WH-FAD^-1. Six (6) species of finfish and three (3) of shellfish of combined total body weight of 368,860 g, were recorded. The dominant families (and species in the study area) were Cichlidae comprising Tilapia guineensis (38.7%) and Sarotherodon melanotheron (31.0%); Claridae (Clarias gariepinus (0.7%) and Palaemonidae, Macrobrachium vollenhovenni and M. macrobrachion recording 0.56%, of total catch.

Key Words: aggregating device, fishes, fisher folks, ondo state, water hyacinth

Introduction

The social-economic hardship experienced by fisher folks in water hyacinth-infested riverine and lacustrine settlements, devoid of industrial and infrastructural developments cannot be overemphasized. It is against this backdrop that this study was conducted in concert with the Ilajes, a sub-ethnic group of the Yoruba tribe, Southwest Nigeria with a view to turning weed to occupational wealth.

Fish aggregation devices can be defined as objects placed in the water bodies such as lagoon, river, stream, and ocean specifically to attract fish for capture. Fish aggregating devices (FADs) could be natural or artificial (man-made) such as structures that float (Castro et al 2002). Dempster (2004) and Boyra et al (2004) reported that the of fish aggregating devices practice began when fishermen noticed that tuna and other pelagic species naturally aggregated under logs, seaweed mats and branches and even near larger animals such as whale sharks, and that fishing improved near these objects or animals. Freon and Dragorn (2000) and Boyra et al (2004) reported that fish aggregating devices are of two categories, namely; anchored or free drifting and floating objects. The usage the two types of FADs depend on geographical areas and fishing gears employed (Franks 2000; Dempster e t al 2002; Boyra et al 2004).

Historically, the idea of grouping fish around floating structures to improve catches comes from traditional coastal fishing. The earliest known use of FADs dates back to 200 AD in the Mediterranean, when the Roman author Oppian described the use of FADs to catch dolphin fish (cited in Tim and Marc 2004; Pepperell 2001). Anderson and Gates (2001) reported that traditional bamboo rafts anchored to the coast called ‘rumpon ‘, ‘unjang’ and ‘payao in Indonesia, Malaysia and The Philippines respectively have been used since the beginning of the 20^th century to attract small pelagic fish. It is generally thought that drifting FADs must be in the water for at least a month to aggregate enough tuna to catch (Itano 2007; Moreno et al 2007). FADs are used widely in tropical and semi-tropical waters by recreational, artisinal and commercial fishers, to concentrate pelagic fish for capture.

Water hyacinth, Eichhonia crassipes (Martius, Solins-Laubauch) has continued to occupy a menace status in Nigeria since its reported invasion of her coastal waters in 1984 (Akinyemiju and Bewaji 2007). Water hyacinth is known to be one of the world’s worst weeds, due principally to its mat-forming nature besides the prolific rate of growth as two parent plants produced 30 offsprings after 23 days and 300 at the end of every month after (Holm et al 2002).

Blachmore and Sullivian (2009) described the water hyacinth as a free floating perennial aquatic plant (or hydrophyte) native to tropical and subtropical South America, with broad, thick, glossy and ovate leaves. Water hyacinth may rise above the surface of the water up to one metre (1m) in height. The leaves are 10 – 20 cm across and float above the water surface, with long, spongy and bulbous stalks. An erect stalk supports a single spike of 8 – 15 conspicuously attractive flowers mostly lavender to pink in colour with six petals (Aquatic plant management society 2008; Blackmore and Sullivian 2009).

In Nigeria, E. crassipes aided by the conducive temperature and humidity, blooms all year round and its capable of doubling its number in 12 – 14 days (Akinyemiju and Bewaji 2007). Akinyemiju and Bewaji reported that the peak of insurgence of this weed in lakes and rivulets’ in Nigeria is between June and September with the highest incidence in July.

The rapid growth and multiplication of water hyacinth account for quick blockage of rivulets and waterways that impedes navigational activities with attendant decimation of active fishing in the riverine communities (Villamagna and Murphy 2009; Malik 2007; Omofunmi 1991). While a school of thought believes in the control and probably eradication of the weed because of its negative social-economic problems, another believes in a judicious utilization of the weed for products such as papers, particle board, matches, fertilizer, etc (Chaitti et al 2013; Oudhis 2004). The vigour that makes E. crassipes one of the world’s worst weed appears to make the plant ideal for water treatment according to Callaway and Wagner (2006). Some aquatic weeds can extract compounds containing nitrogen and phosphorus, which are common pollutants from water and incorporate them into their own structure. According to Researchers such as Oudhis (2004); Callaway and Wagner (2006) and Chaitti (2013) have found that water hyacinth can be useful for treatment of sewage effluent so that dissolved nutrients are recovered for reuse. There are a lot of the Water Hyacinth all over the rivers, creeks and lagoons in the riverine in Ilaje Local government Area of the State. The branches of trees have being used as aggregating device in the area. The Water hyacinth was used to serve as alternative to the branches of tree and it has advantages over tree branches due to ease decaying in short time and its residue can also served as organic manure. This study was to assess the economic important of Fish Aggregating Device in Riverine area of Ondo State.

Materials and Methods

The two-year study was conducted in four phases each spanning three months, precisely October – December and February – April 2014 and 2015

Design of Fish Aggregating Device (FAD)

To construct an FAD measuring 30 x 6 m (0.18 ha), bamboo poles were used as side frames, guided with tree trunks planted into the riverbed soil of 1.5 m mean water depth. Twelve 2 x 1 m rectangular bamboo pole frame works covering 1.3 % of (FAD) water surface area were symmetrically positioned to allow for direct insolation (Fig. 1)

Figure 1. Module of Water Hyacinth- Fish Aggregating Device

Ten (10) of such FADs were used as passive extensive culture receptacles, with each isolating 1800 m² (0.18 ha) of rivulets and creeks.

Collection of baseline data in the FADs

Baseline data were collected at 15 days intervals for 3 months culture period and these include:

(a) Water quality,

(b) Pelagic and macro-benthic biological communities.

Samples was done twice a month for three month culture

Water Quality Analysis

To obtain information on the physical and chemical properties of the isolated water, samples were collected at intervals of 15 days and analyzed, employing Standard methods (APHA 2005) for salinity, dissolved oxygen, pH, turbidity, total Kdejahl nitrogen and phosphorus.

Pelagic and macro benthic biological communities

Sampling preparation (Fauna and Flora) from water hyacinth (E. crassipes) using their roots and stolons from the foliage part, were randomly picked from the FADs colonies. Both roots and stolons were preserved in buckets with 5 % formalin and subsequently vigorously shaken to dislodge the fauna and flora. To harvest macro benthic organisms, the raw water was filtered through 333 mesh Endicott’s sieve into another container. The organisms so retained in the sieve were washed into glass bottles and preserved in the 5 % formalin. Epiphilic algal samples were retrieved from a 100 mesh filter. These samples were further concentrated using a 55 mesh size Hydro bios plankton bucket and preserved in mixture of iodine and 4 % formalin (Everhart et al 2005). Aliquots from each sample were sorted into major taxa and counted using an Olympus Vanox Research microscope. Identification and classification work done on the specimen collected were done after Eborge (2008).

Cropping techniques from WH-Fish Aggregating Device (WH-FAD)

To crop fish at the end of the third month of extensive cultivation, different fishing gears were employed. The gears used, ranged from fine-mesh encircling net, long woven raffia palm, bamboo bark wrapped around the periphery of the FAD sometimes with intermittent openings for introducing basket traps, cast and set nets to hand-pressed conical traps.

The array of gears could only be effectively used by sweeping the FAD of all floating and bed-rooted obstacles. Consequent upon the fact that the fish shelters are undrainable, yield from catch was estimated employing the well-known Peterson Ratio using marked fish (Everhart et al 2005).

Estimation of Fish Yield from WH-FAD Extensive Culture Receptacles

The estimate catch was determined using Peterson Ratio of marked fish. Random samples were collected, marked, and released and later on recaptured to include both marked and unmarked fish (Everhart et al 2005).

Results

Physical and chemical parameters, floral classes and faunal phyla of water sample in WH-FAD estimated in the Tables 1, 2 and 3 respectively.

Table 2 shows the number of order per class identified in the study.

Four (4) floral classes were identified include Bacillariophyceae, Chlorophyceae, Chyrsophyceae and Cyanophyceae. Pennales Order of the Class of Bacillariophyceae had the widest spectrum of species (Table 2).

Six (6) faunal phyla were identified and these were, Phylum: Chordata, represented by the pisces. Phylum: Protozia; Phylum: Rotifera; Phylum: Nematoda; Phylum: Annelida and Phylum: Mollusca (Table 3).

Table 4 shows the spectrum of species caught as well as their total body weights, numbers and invariably mean weights. The cichlids,S. melanotheron of mean body weight, 250 g and T. guineensis of mean body weight, 220 g, were most abundant among the finfish. While 1,200 g mean body weight was recorded for C. obscura, the highest mean weight of 1,350 g was attained in the culture receptacles by C.gariepinus. Among the shellfish, the highest mean body weight of 450 g was recorded for M. machrochium.

Discussion

From this study, water hyacinth can be economically employed as a fish-aggregating device for extensive fish production by riverine fisher folk.

The results obtained from analysis of water sample of Fish Aggregating Device were suitable for fish production (Ronald et al 2006; Omitoyin 2007).

The floral and faunal composition was impressive and suggested build-up of natural fish foods in the culture receptacles. For instance, it is a common knowledge that the composition of fish at a given locality is the result of the operation of a series of shelter while the speciation process determines the total complement of species that could be present. Most of the fishes that inhabit these fish shelters are small (less than 10 cm standard length). This size allows them to seek shelter in the maze of the roots of the weeds and the delicately arranged brush park scouting for foods.

The enormous mean body weights attained by some of the piscivores, C. obscura and C. gariepinus among others are traceable to the readily available small fish as natural food. The adaptive ability of the cichlids to salinity variation besides the biological museum; the phyto- and zoo benthic communities associated with water hyacinth fish aggregating accounted for the relative abundance of the species constituting 38.9 and 31.0 % respectively.

Impressive fish yield of 368 86 WH-FAD or 3.7 tons (0.18 ) of water body was recorded in the study as against 0.937 conventional brush park FAD isolating 0.8 ha water body (Solarin 2001). Fish yields from the ten Fish aggregating device (FADs) employed in this study showed that the diversity of fishes in the FADs tends to increase with an increase in area, depth and indices of productivity.

In spite of the non-drain ability nature of the WH-FAD system, the estimated fish population recorded, that is 2,200 WH-FAD^-1 which falls within the range of calculated values,(1,939 = 0.95 confirms the degree of Catch per unit effort (C.P.U.E) obtained by the fisher folks. The 2 x 1 meter intermittent water surface openings created in the mat of water hyacinth colony in this study not only create room for direct solar penetration meant for photosynthetic activities but also enhanced free dissolution of atmospheric oxygen needed by the flora and fauna communities in FAD

Conclusion

• It can conclude from this study that water hyacinth; despite its acclaimed nuisance value is of immense economic importance when utilized appropriately.

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Received 30 January 2017; Accepted 7 December 2017; Published 1 January 2018

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