The Performance of Rotifer Brachionus plicatilis (Müller 1786) and Chicken Egg Yolk on the Larval Rearing of African Catfish, Clarias gariepinus (Burchell 1822) in Hatchery   

Godfrey William Ngupula , Magreth Musiba
Tanzania Fisheries Research Institute (TAFIRI), PO Box 475, Mwanza, Tanzania
Author    Correspondence author
International Journal of Aquaculture, 2014, Vol. 4, No. 2   doi: 10.5376/ija.2014.04.0002
Received: 31 Oct., 2013    Accepted: 18 Dec., 2013    Published: 10 Jan., 2014
© 2014 BioPublisher Publishing Platform
This is an open access article published under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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Ngupula and Musiba, 2014, The Performance of Rotifer Brachionus plicatilis (Müller 1786) and Chicken Egg Yolk on the Larval Rearing of African Catfish, Clarias gariepinus (Burchell 1822) in Hatchery, International Journal of Aquaculture, Vol.4, No.02: 12-19 (doi: 10.5376/ija.2014.04.0002)

Abstract
The possibility of utilizing rotifer Brachionus plicatilis (Müller, 1786), broiler chicken egg yolk, and a mixture of the two as starter feeds in the larval rearing of African catfish (Clarias gariepinus, Burchell, 1822) was explored. Larvae of four days following commencement of exogenous feeding were used for the purpose. The experiment lasted for 15 days under ambient hatchery conditions in a set of nine tanks of 900 litres capacity randomly allocated. The experiment was carried out in two phases.  In the end of each phase, the larvae from each set of tanks were counted and from each feed treatment 30 larvae were randomly chosen and measured their weights and lengths for the estimation of average weight and length. The average lengths of the larvae from each phase and each feed treatment were used for the estimation of growth rates, survival %, specific growth rate (SGR), and conditional factor (CF).  During the 1st phase, the larvae fed with rotifers indicated the highest survival (98%) with poorest growth rate (25.76%/day). During the 2nd phase (weaning period), the larvae fed with rotifers indicated the poorest survival (54%) while those fed with egg yolk indicated the highest growth (weight and length of 19.85±3.66mg and 12.13±0.60mm, respectively) and survival of 61%. The findings imply that rotifers are too small for the rearing of African catfish larvae, thus unsuitable. Chicken egg yolk can successfully be used as a substitute of live diet for rearing of African catfish larvae if need arises.
Keywords
Brachionus plicatilis; Feed; African Catfish; Growth rate; Survival; Weaning; Weight

Introduction
Nile tilapia Oreochromis niloticus (Linnaeus, 1758) and African catfish Clarias gariepinus (Burchell, 1822) are the most important farmed fish species as regards to African fresh water aquaculture (El-Sayed, 2005; Olurin and Oluwo, 2010; Khalill et al., 2011; Olurin et al., 2012). The reasons behind the choices are mainly fast growth rate, high tolerance to poor water quality, ability to utilize variety of diets, and ease of breeding in captivity (Olirin and Oluwo. 2010; Olurin et al., 2012). As regards to breeding, the rearing of C. gariepinus larvae to juveniles has proved as an important challenge because of their small size and lack of functional digestive system at commencement of their exogenous feeding (mouth opening) period (Govoni et al., 1986; Olurin et al., 2012). Thus, making them incapable of accepting large sized feeds and assimilating protein from dry formulated diets (Govoni et al., 1986; Zambonino Infante and Cahu, 2001). Due to this fact, it has been found important to provide the larvae with live feeds like Artemia, zooplankton (such as cladocerans and rotifers) or algae first before they are sequentially acclimatized to accepting formulated diets (Olurin and Oluwo, 2010; Khalill et al., 2011; Olurin et al., 2012). Provision of live feeds to fish larvae is appreciated as important because they supply nutrients to the larvae and as well exogenous enzymes important for the digestion of other feeds, and enhance the development of larvae’s pancreas (Rønnestad et al., 1999; Lubzen et al., 2001).
Globally, rotifers, especially of the species Brachionus plicatilis Müller, 1786and Brachionus rotundiformis Tschugunoff, 1921 have been used for years second to Artemia for the rearing of marine fish larvae (Boehm et al., 2000; Lubzen et al., 2001; Olivotto et al., 2010). The reasons behind their use include their tolerance to wide range of environmental conditions, high reproductive efficient (both sexual and asexual), easy of manipulation to suit certain nutrition requirements, slow mobility, small size, and colour (Theilacker and McMaster, 1971; Fukusho, 1989; Lubzen et al., 2001). Despite the increasingly wide use of the mixo-haline rotifer B. plicatilis in the marine fish laviculture, there are no records on the culture and use of the fresh water B. plicatilis as live feed in the fresh water fish larviculture. Therefore, any efforts to culture the fresh water rotifer B. plicatilis and its consecutive use in the rearing of any of the fresh water fish larvae would be appreciated as important to the large scientific community of the world.
Currently, as aquaculture industry is expanding, also the technologies in processing fish feed into various formulations including the micro-dry diets for fish larvae are also increasing. In East Africa, some local fish farmers use boiled chicken egg yolk for the rearing of C. gariepinus larvae. However, the feed has never been researched and recommended for its suitability. Chicken egg yolks are appreciated of having diversity of nutrients like vitamins, amino acids, and high content of lipids, however with a bit low protein content as compared to the high demand of C. gariepinus larvae (Krawczyk, 2009). Therefore, any efforts to experiment the suitability of the feed in the growth and survival of the larvae would be appreciated by many as important especially in the regards of promoting local technologies and innovations. Generally, East African aquaculture industry is relatively undeveloped despite of much potential for its growth. In those countries, of the major obstacles towards the growth and ultimate development of the industry is the unavailability of cheap technologies in place to lead into affordable quality fish feed and seed (Mwanja et al., 2006; FAO, 2006). And, knowledge on the technical knowhow in artificially manipulation of C. gariepinus broods to lead to larvae and its rearing processes is limited. In West Africa (i.e. Nigeria), Artemia feeds (decapsulated from its cysts or packed as dry diets) are the most widely used feeds for the rearing of larvae of C. gariepinus and its hybrid, Heterobrachs (Olurin and Oluwo, 2010; Olurin et al., 2012).
This study intended at mass producing the fresh water rotifer B. plicatilis and explores its performance on the rearing of C. gariepinus larvae. The performance indices monitored were growth rate (GR), Specific Growth Rate (SGR), survival percentages, and conditional factor (CF). The study also explored the performance of chicken egg yolk on the rearing of the same. The hypotheses of the study are: (a) Rotifers can offer proper growth in the C. gariepinus larvae (b) Egg yolk perform well in the rearing of African catfish larvae, thus can be a good substitute for live feeds.
1 Results
During the 1st phase of the experiment, there were significant differences (F = 768, p < 0.01, Table 1) in growth performances of the three feeds fed to the African catfish larvae. The African catfish larvae fed with egg yolk indicated the highest growth rate (60.42%/day), survival of 83% and SGR of 0.28. In terms of growth rate (42.76%/day), the larvae fed with mixture of egg yolk and rotifer performed the second to egg yolk. The feed indicated survival rate of 87% and SGR of 0.23. The larvae fed with rotifer indicated the poorest growth rate (25.76%/day) and SGR (0.16), however with highest survival percentages (98%) (Table 1).

 

 

Table 1 Growth rate, SGRs, and survival percentages of the Clarias gariepinus larvae fed with chicken egg yolk, rotifer(Brachionus plicatilis) and a mixture of the two during the 1st phase (the first five days) of the experiment.

Note: Values with same superscript in a row mean that were not significant different.

 

During the 2nd phase (weaning) of the experiment, there were significant differences in growth performances of the African catfish larvae (F = 418, p < 0.01, Table 2) with larvae fed on egg yolk performing best (weight and length of 19.85±3.66mg and 12.13±0.60mm, respectively, and survival of 61%). The performance of larvae fed with mixture of egg yolk and rotifer was between the two diets. Contrasting the 1st phase, in this phase the larvae fed with rotifer indicated the poorest survival (54%) (Table 2).

 

 

Table 2 Growth rate, SGR, and survival percentages of Clarias gariepinus larvae fed with chicken egg yolk, rotifer (Brachionus plicatilis), and a mixture of the two during the 2nd phase of the experiment

Note: Values with same superscript in a row means that were not significant different


There was significant variation in water quality parameters as measured in the different feed treatments (One–Way ANOVA
with Tukey’s HSD post hoc test, F=1673,p<0.01, Table 3). DO indicated a range (lowest to highest) of 5.31±0.61 to 6.30±0.14 mgO2 L−1. Temperature and pH indicated ranges of 21.53±0.11 to 24.30±0.42? and 5.65±0.21 to 6.79±0.24, respectively. 

 

 

Table 3 The pH, temperature, and dissolved oxygen (DO) as measured in the tanks with different feed treatments during the 1st and 2nd phases of the experiment n = 14

Note: nsd = not significant different while sd = significant different

 

 

The rotifer B. plicatilis had the highest crude protein content (25.11%) followed by egg yolk(15.95%) (Table 4).

 

 

 

Table 4 Proximate analysis of egg yolk and the rotifer B. plicatilis

 

2 Discussions
The rotifer B. plicatilis indicated the poorest growth rate in the larval rearing of African catfish while chicken egg yolk performed the best. We attribute this finding with the fact that B. plicatilis are very small in size as compared to the mouth size of the African catfish larvae at commencement of their exogenous feeding period. The rotifers which had higher crude protein than egg yolk, if not the constrain of size then would have been  expected to perform better than egg yolk. According to Lubzens et al. (2001), when using rotifers as a feed, normally the number of rotifers consumed would determine the quantity of food reaching the gut of the larva. In our case, the larvae fed with rotifers possibly spent most of their time eating while having only little of the food reaching their guts for translation to growth. Generally, rotifers are worldwide appreciated as good starter feed for the rearing of most marine fish larvae (i.e. codfish) which are small in size during commencement of their exogenous feeding (Lubzens et al., 2001; Yilmaz et al., 2006; Olivotto et al., 2010). The occasional poor performance (growth and survival) of rotifers in the rearing of marine fish larvae (when compared to other live feeds like copepods) normally is attributed to its imbalances in fatty acids composition rather than its size (Olivotto et al., 2010). So far, there no records that have confirmed the suitability of rotifers in the rearing of either C. gariepinus larvae or any other fresh water fish larvae. This is because most fresh water fish larvae are appreciated as are of large size at the time of their first feeding, thus requiring big sized food particles such as cladocerans and copepods (Yilmaz et al., 2006). According to Yilmaz et al. (2006), African catfish larvae normally have mouth size big enough to even ingest some big sized zooplankton such as copepods and cladocerans at the time of their first feeding.
Generally, as regards to this study, both diets indicated poor growth and the lowest survival % during the weaning period, especially rotifers. This fact could be implicated with immaturity of the digestive system of African catfish larvae in that period. According to Rønnestad et al. (1999) and Lubzen et al. (2001), live feeding fish larvae is important for the supply of nutrients and exogenous enzymes important for the digestion of other feeds and enhancement of the development of larvae’s pancreas. And, according to Olivotto et al. (2010), the length of metamorphosis time during the larval phase also depends on the type of administered feed to larvae and has implications on survival and growth. Therefore, the indicated poor survival percentages and poor growth of the larvae from the three treatments is because of the indicated poor nutritional quality of the diets and thus failed to supply the necessary nutrients and enzymes for larvae growth and digestive system development. Thus, egg yolk and rotifer cannot be recommended as first choice for the profitable rearing of catfish larvae, unless for assuring survival in risks of mass mortality.
As compared to other feeds, the performance (growth and survival) of chicken egg yolk was good. The finding implies that the feed contains simple absorbable compounds important for the larvae in a certain reasonable ration (Krawczyk, 2009). In the regards of the objectives of sponsors of this study, for example, promotion of simple technologies to lead into availability and affordability of quality fish seed to poor farmers, the finding is appreciated as of quite important. Of the major problems when using egg yolk as a feed for the fish is that, water quality get degraded very fast thus raising the risk of increased larval mortality due to quick development of ammonia. This is because the likeliness to oversupply the feed is high, thus resulting into high food remains in the rearing media. The mixture of rotifer and egg yolk feed performed the second after egg yolk. This study expected this feed treatment to perform better than using egg yolk alone due to broad spectrum of nutrients provided, and so far we are not in position to account for the observed situation.
Generally, DO values as monitored during our experiments were in a range acceptable (5.31±0.61 to 6.30 ± 0.14 mgO2 L−1) for a farmed fish. According to Beveridge et al. (1993), a minimum of 3 ppm of DO at temperature between 25?-30?is suggested as ideal for fish farming in fresh waters. However, the recorded temperature values, a range of 21.53±0.11 to 24.30±0.42? were less than the suggested range of 25 to 30? (Britz and Hecht, 1987; Beveridge et al., 1993). It is quite probable that the generally bad results (in terms of growth in size and survival) we got during this time experiments (as compared to the past ones) are contributed by the observed low temperature conditions in the hatchery. Higher temperature in hatchery (i.e. 30?) is highly recommended for improved hatching rate, growth, and survival (Britz and Hecht, 1987). Temperature is positively associated to egg developmental processes and metabolic activities of the larvae after hatch (Ouellet et al., 2001; Hamoutene et al., 1999; Hamre, 2006; Suzer et al., 2006).
3 Materials and methods
3.1 Preparation for African Catfish larvae
Nine African catfish (three females of 450g, 500g, and 600g and six males of the size range of 1300g-1500g) were collected from wetland areas in the upper catchments of Lake Victoria in Misungwi district and used in the artificial propagation processes to lead to larvae. After arrival at Tanzania Fisheries Research Institute (TAFIRI)-Mwanza station, the fish regardless of their sex were stored for some time in an outdoor concrete pond of 10m x 10m size to stabilize them physiologically and acclimatization for reproduction. The female fish were then taken into TAFIRI hatchery and injected with an Ovaprim hormone (a synthetic hormone used as a substitute of catfish’s male pituitary hormone) at a concentration of 0.5ml/kg fish to induce an ovulation process (Adebayo et al., 2008; Olumuji and Mustafa, 2012).
Thereafter, each hormone induced female fish was kept in a white plastic tank of 900 litres capacity and left for 13hours (from 18.30hrs to 7.30hrs-latency period) at a room temperature of 25.1±0.4? before was striped. Catfish females were considered ripe if had distended abdomen and eggs oozed freely when the abdomen was gently pressed anterior posteriorly while ripe males had genital papilla reddish in colour (Olumuji and Mustafa, 2012). Before striping the female fish to obtain the eggs, it was important that a sperm solution (milt) was prepared first. One to two male catfish were sacrificed to fertilize the eggs of one female.
The milt was obtained by dissecting the male catfish and the respective tips of the ripe tests cut and sperms squeezed into 10ml saline water (Saline water: NaCl dissolved in distilled water) (Olumuji and Mustafa, 2012). The time interval since making the milt and stripping of eggs to allow fertilization averaged 5 minutes. The female fish was weighed using a 10kg capacity weighing balance before stripping and its eggs were weighed too (using a 1000g capacity weighing balance with a sensitivity of 0.01g) and their total number calculated. For fertilization to effectively take place, the mixture of milt and eggs was carefully and gently stirred for approximate one minute. Thereafter, the fertilized eggs of each female were evenly spread with assistance of a chicken feather in 45cm x 45cm potassium permanganate pre-treated trays (made using a net of 30µ mesh size) and incubated at mean room temperature of 25.1±0.4? in tanks of 900 litres capacity and maintained at a flow through system of water to allow dissolved oxygen of 5.83±0.45mgO2 L−1. Soon after hatching (averagely 26 to 27 hours since incubation), the incubation trays were washed with water, soaked with potassium permanganate and dried in the sun ready for the next re-use.
The hatched larvae were left for four days before the commencement of exogenous feeding (mouth opening period).  In the fifth day, the larvae from the three fish were mixed together in one separate tank and then randomly reallocated into nine experimental tanks (white plastics of 900 litres capacity) for the test of performance of rotifer B. plicatilis, chicken egg yolk, and mixture of egg yolk and B. plicatilis feeds.Each tank averagely contained a total of 600 larvae.
Before the start of the experiments, some representative larvae were randomly chosen, and then measured their weight and total length to obtain their initial average weight (g) and length (mm). The used nine tanks (each feed treatment at replicate of three) were maintained at flow through system from water directly pumped from Lake Victoria, then filtered, aerated, and allowed to flow under gravity to the tanks in hatchery. The larvae in both tanks were fed three times a day, at 9.00hrs, 13.00hrs, and 16.00hrs. Concurrently with feeding, also physical and chemical parameters like pH and temperature were monitored three times a day using a portable pH-Temperature meter (HI 991300 pH/EC/TDS/Temperature meter) while dissolved oxygen (mgO2 L−1) was measured using a portable Oxygen meter (HI 9143 Microprocessor Oxygen meter HANNA instruments) in the duration of the experiment.
3.2 Preparation and application of the feeds
To mass culture B. plicatilis, tape water was filled in three black plastic tanks of 900 litres capacity and then left for two days to allow de- chlorination. In the third day, each tank was fertilized with 3kg of local chicken manure wrapped in a perforated plastic bag. After two days since fertilization, the tanks were inoculated with 5 litres of water containing phytoplankton and 1 litres of solution of B. plicatilis. Thereafter, the tanks were left for 10 days to allow growth of phytoplankton and the rotifer. After this period, the rotifers in the tanks had already multiplied to a density of > 2000 individuals in a litre of water. Rotifers were concentrated using a zooplankton net of 60µm to make a feed of the day. During feeding, the larvae of C. gariepinus aimed at testing the performance of B. plicatilis were supplied with 500ml of its solution at each feeding interval as specified above. In each day, one chicken egg was boiled and the yolk measured its weight. At each feeding interval, 10g of the yolk was used to make a solution of 1.4 litres used as feed of the day.  Each tank with the larvae tested for egg yolk was supplied with 100ml of the solution.  And those tested for egg yolk and rotifers, the feed was mixed in a proportion of 1:5, thus each tank was supplied with 50ml of solution of egg yolk and 250ml of a solution of rotifer three times a day. The amount of feed was adjusted as per the larvae requirements with time and during each feeding the larvae were fed to satiety. Some samples of the dried B. plicatilisand egg yolk were taken to Sokoine University of Agriculture (SUA) for proximate analysis of crude protein, lipid, crude fibre, and ash contents.
3.3 Set up and duration of the experiment
The feeds performance experiment lasted for 15 days and was divided into two phases. The 1st phase which comprised the first five days since the commencement of exogenous feeding aimed at giving the larvae with live feed parcel. The second phase (weaning period) lasted for 10 days and aimed at acclimatizing the larvae with a dry formulated diet. During weaning period, the larvae were fed with the live feed plus the Ugarchick (35% crude protein, 7% lipid, 6.5 % crude fibre, 7% ash, and 11% moisture) in a substitution manner. At the end of each phase, the larvae in the nine tanks were randomly sub sampled to obtain 10 larvae from each tank, totalling to 30 larvae for each feed treatment. The larvae were weighed to the nearest 0.0001mg (using a 220g capacity and 0.0001g sensitivity balance, Model Sartorius, CPA 224S 23750418, USA). The total lengths were also measured to the nearest 0.1 millimetre using a 30cm ruler. The faeces and uneaten food at the bottom of each tank including the dead larvae were pumped out daily at 08.00hrs using a 1cm thick and 5m long pipe. While the dead larvae were counted for the calculation of survival %, the live larvae were separated from the impurities and returned to the tanks.
3.4 Growth performance indices
Growth parameters were determined using both length and weight following the formulas provided in Olurin et al. (2012):
GR = 100× (Wf - Wi)/(T x Li)…………....…..…. (i)
GR = 100 × (Lf - Li)/(T × Li)………............…… (ii)
SGR = (ln Wf - ln Wi)/(T2 - T1)……………..….... (iii)
SGR (mm/day) = (ln Lf - ln Li)/(T2 - T1) …….. (iv)
SR (%) = 100 × Ns/N­i …………….………......……. (v)
Where GR = growth rate, SGR = specific growth rate, SR = survival rate; Wf = final weight (mg), Wi = initial weight (mg), Lf and Li represent final and initial lenghts in mm respectively; T = time in days, T1 and T2 represents initial and final time (days); Ns and Ni represents number of survivors and initial number of fish respectively.
The condition factor of C. gariepinus larvaewas calculated according to Madu et al. (2003):
CF = 100 × W/L3…………………..........….....……. (vi)
Where w = weight of fish in mg, L = length of fish in mm. 
3.5 Statistical analysis
One-way ANOVA test was used for the test of significance in growth performance and water quality parameter differences among the treatments. The analyses were done using SPSS version 17 (SPSS Inc, USA).
4 Conclusions
The rotifer B. plicatilis is not a suitable feed for the larval rearing of farmed fresh water fish like African catfish if profitability is important. Generally, because both diets tested indicated poor growth and survival, this study does not recommend any at first choice, unless for assuring survival at risks of mortality. Of the diets tested, chicken egg yolk can somehow work well as a good start feed in the larvae rearing of African catfish. While choosing feed for the larvae, it is important that the regards of deterioration of water quality are taken care, as the larvae of African catfish have indicated as not strong in tolerating stresses highly contrasting their adults.
Acknowledgments
We wish to recognize the Association for Strengthening Agricultural Research in Eastern and Central Africa (ASARECA) for sponsoring this study. We also appreciate the cooperation of TAFIRI staff during the execution of this study.
Authors’ Contributions
GWN and MM together designed the study and had full cooperation in the writing of this manuscript. GWN cultured the rotifer, supervised the experiments, analyzed the data, and prepared a first draft.
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