Raeesah Ameen, Gan Moodley, Deborah Robertson-Andersson. Presented at the ninth Scientific Symposium of the Western Indian Ocean Marine Science Association (WIOMSA) 2015.

1. THE USE OF SUB-TROPICAL EAST COAST COPEPOD
SPECIES AS LIVE FEED FOR FISH LARVICULTURE
INTRODUCTION
 The sustainability of marine fin fish significantly relies on the production cost
relative to yield 1. One of the main challenges facing this industry is the
availability of a cheap nutritional food source for rearing marine larvae.
 Many marine fish larvae feed on smaller zooplankton species. This is due to
poor visual accuracy and a limited gape size , which consequently relies
on the inherent movement of zooplankton for larvae to feed on2.
 In marine aquaculture, Artemia and rotifers are commonly used as feed. In
comparison to rotifers and Artemia, copepods have been proven to
increase the survival and growth rate of marine larvae due to their
excellent fatty acid content and adequate docosahexaenoic acid (DHA) to
eicosapentaenoic acid (EPA) ratio1.
 This study aims to: (1) compare copepod species abundance, richness and
distribution along the Mlalazi estuary and Mtunzini fish farm (Fig. 4)
located on the east coast of South Africa; and (2) identify an alternate
copepod food source for dusky kob larvae, by determining their optimum
salinity and temperature ranges (Fig. 5-7).
 This experiment can be used to advance the aquaculture industry by
providing a cheap, local and nutritional source of food for marine larvae.
The results obtained can also be used by the Mtunzini fish farm to provide
an adequate food source for their dusky kob larvae.
METHODS
Study Site
Sample collection
The copepods were collected during the day and night by vertical tow using a plankton
net.
Experiment 1 (Fig. 2): Samples were fixed using 10% formalin, stained using rose
Bengal and analysed for species abundance and richness, using three 20 ml sub-
samples.
Experiment 2 (Fig. 3): Live copepod samples (species 1 & 7) in aerated honey jars
were subjected to three different temperatures and salinities to test survival, with three
replicates each3 .
Sample statistics
As data was non- parametric (p< 0.05) a Kruskal-Wallis test was used to determine
whether treatments and sites were identical, followed by a linear regression model to
compare (a) species and sites for experiment 1 and (b) the treatments for experiment 2.
All statistical analyses were conducted using Rcommander, version 3.2.2.
RESULTS
• Highest abundance occurred in site 4 (Day), and site 2 (Night). Species 1 was the most abundant during day and night (Fig. 4A & B).
CONCLUSIONS
• Species abundance decreases along the Mlalazi estuary from the head (site 4) to the mouth (site 6) which is probably due to the changes
in salinity and temperature.
• Copepods species richness in the fish farm and estuary is higher at night (6 spp.) than during the day (4 spp.).
• Highest survival of copepod Pseudodiaptomus hessei (Mrázek, 1894) occurs at high temperatures (27 °C) and low salinities (25 psu), while
that of harpacticoid species 7 occurs at low temperatures (18 °C) and high salinities (35 psu).
• We recommend than an alternate copepod food source for dusky kob larvae is Pseudodiaptomus hessei (Mrázek, 1894), due to their
shared preference for high temperatures and low salinities.
REFERENCES
[1] Kassim, Z., John, A., Chin, L. K., Zakaria, F., & Asgnari, H., 2014. Sustainable Technique for Selected Live Feed Culture. Sustainable Aquaculture Techniques, Chapter 4: 105–133.
[2] Graeb, D. S. B., & Dettmers, M. J., 2004. Fish Size and Prey AvailabilityAffect Growth , Survival , Prey Selection , and Foraging Behaviour of Larval Yellow
Perch. Transactions of the American Fisheries Society, 133: 504–514.
[3] Vengadeshperumal, N., Damotharan, P., Rajkumar, M., Perumal, P., Vijayalakshmi, S., & Balasubramanian, T., 2010. Laboratory Culture and Biochemical Characterization of the
Calanoid Copepod , Acartia southwelli Sewell, 1914 and Acartia centrura Giesbrecht, 1889. Advances in Biological Research, 4(2): 97–107.
• The highest average survival of Pseudodiaptomus hessei
(Mrázek, 1894) over a 4 day period, occurred in treatment
6 (27 °C, 20 psu) with a survival of 42 %, followed by
treatment 7 with 36 % survival (27 °C, 25 psu) (Fig 5).
• The average survival in treatments was higher than the
control (30 %) (23 °C, 28 psu). The lowest survival
however was observed in treatment 4 (27 °C, 35 psu),
with a value of 22 %.
• The highest average survival of harpacticoid (species 7)
over a 4 day period (Fig. 6), occurred in treatment 9 (20
°C, 35 psu) with a value of 74 %.
• The survival was higher than observed in the control (52
%) (20 °C, 30 psu). The lowest survival however, was
observed in treatment 5 (27 °C, 30 psu), with a value of
38 %.
• The highest average survival of harpacticoid (species 7)
over a 13 day period (Fig. 7), occurred in treatment 9 (18
°C, 35 psu) with a value of 40 %, followed by
treatments 1 (39 %) (23 °C, 25 psu).
• The survival was higher than the control (31 %) (22 °C, 31
psu).
Figure 4A & B: Average copepod abundance, richness and distribution at each site along the Mtunzini fish farm (site 1-3) and Mlalazi estuary
(site 4-6) during the day (4A) and night (4B) (+/- SE)
Figure 5: Experiment 2.1 average survival of copepod Pseudodiaptomus
hessei (Mrázek, 1894) at different temperature and salinity
treatment (T) combinations per day, with replicates (+/- SE)
Figure 6: Experiment 2.2 average survival of copepod species 7
(harpacticoid) at different temperature and salinity treatment
(T) combinations per day, with replicates (+/- SE)
Figure 7: Experiment 2.3 average survival of copepod species 7
(harpacticoid) at different temperature and salinity treatment
(T) combinations per day, with replicates (+/- SE)
Figure 8: Copepod species 1-7 observed in the study. 1) Calanoid- Pseudodiaptomus hessei (Mrázek, 1894); 2) Unknown (potential Pseudodiaptomus
hessei (Mrázek, 1894) juvenile); 3) Calanoid- Arcatia natalensis (Connell & Grindley, 1974); 4) Cyclopoid; 5) Harpacticoid; 6) Cyclopoid; 7)
Harpacticoid
Figure 1: Mlalazi estuary (28⁰55’54” S; 31⁰44’04” E) located on the east
coast of South Africa (sites 1-water inlet, 2– pond, 3-hatchery);
and the Mtunzini Fish Farm (28⁰56’09” S; 31⁰45’55” E) is located
near the estuary (sites 4– head, 5– middle, 6– mouth).
Figure 2: Copepods stained with rose bengal
Figure 3: Copepods subjected to varying salinity and temperature combinations
1
A B
ACKNOWLEDGEMENTS
We thank Niel Stallard (Mtunzini Fish Farm) for permission and assistance to
collect water samples and UKZN for funding assistance.