Lober, Malwine (2015) Investigation of the aquaculture potential of an Australian freshwater prawn, Macrobrachium spinipes (Schenkel, 1902), with emphasis on spawning induction, larval and nursery culture. Masters (Research) thesis, James Cook University.

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Abstract

Modern aquaculture of freshwater prawns began in 1960's after the life cycle of Macrobrachium rosenbergii was first closed. The industry has since expanded rapidly with global annual production reaching 443,959 tonnes in 2009. The Australian native freshwater prawn species formerly known as M. rosenbergii was recently renamed as Macrobrachium spinipes. The past attempts to commercially culture the native Australian freshwater prawn has never taken off citing various problems. In view that new molecular evidence showed native Australian freshwater prawn encompasses four lineages, this study investigated broodstock management, larval and nursery culture techniques for the lineage II M. spinipes sourced from tropical north Queensland.

Spawn induction of M. spinipes outside its natural breeding season (November to March) was investigated by temperature and photoperiod manipulation. Mature females (15) were kept individually under controlled water temperatures of 24, 27 and 30 °C with photoperiod adjusted to 14.5 h light: 9.5 h dark while the control was under ambient conditions. The experiment ran from May to August for 84 days and throughout the experimental duration, no spawning was recorded in any treatments. Despite ambient temperature dropping to as low as 12 °C for the control, no mortality was recorded in all treatments except a single death found for 30 °C treatment and common moults occurred in all treatments even during the coldest period in the control. Hence M. spinipes showed high tolerance to low water temperature and potential for grow-out culture under cooler climates.

The effects of microalgae Nannochloropsis sp. addition and concentration ('green water') on larval survival, development and growth of newly hatched larvae of M. spinipes were investigated under the condition of no algae addition ('clear water') and four Nannochloropsis concentrations of 2.5, 6.25, 12.5 and 25 x 10⁵ cells ml⁻¹. Survival to PL at the two higher algae concentrations of 12.5 and 25 x 10⁵ cells ml⁻¹ (70.8 % and 63.3 %, respectively) were significantly higher (P<0.05) than the two lower concentrations and the 'clear water' treatments (26.7 %, 35.0 % and 30.0 %), respectively. Meanwhile, the fastest mean development to PL (30.6 days) was obtained at the highest algal density, which was 14 days shorter than that of the 'clear water' treatment (44.3 days). Mean dry weights of newly settled PL's in the two high algal density treatments were also significantly heavier (P<0.05) than in the lowest algal density and the 'clear water' treatments. The results clearly showed that in comparison with the 'clear water' method, 'green water' culture by adding Nannochloropsis sp. potentially could substantially improve larval performance of M. spinipes, however such beneficial effects only became significant when the concentration of algae added reached a threshold level.

A further experiment was conducted to evaluate the effects of addition of higher microalgae concentrations as compared to Artemia enrichment on larval growth, survival and fatty acid composition of M. spinipes larvae and their interactions. The newly hatched larvae were cultured with no addition of algae ('clear water') and Nannochloropsis sp. added ('green water') at two concentrations of 2.5 (low) and 10 x 10⁶ cells ml⁻¹ (high) and fed with either enriched or non-enriched Artemia: i.e.1) 'clearwater' + enriched Artemia; 2) 'clearwater' + non-enriched Artemia; 3) 2.5 x 10⁶ cells ml⁻¹ + enriched Artemia; 4) 2.5 x 10⁶ cells ml⁻¹ + non-enriched Artemia; 5) 10 x10⁶ cells ml⁻¹ + enriched Artemia and 6) 10 x10⁶ cells ml⁻¹ + non-enriched Artemia. The results showed that under 'clear water' culture, larvae fed nonenriched Artemia resulted in total mortality while Artemia enrichment improved survival to 18 %; at the low algal density (2.5x10⁶ cells ml⁻¹), larval survival also improved with Artemia enrichment (55.8 vs. 80 %). However, survival was very similar with and without Artemia enrichment at high algal density of 10x10⁶ cells ml⁻¹. 'Clear water' culture resulted in poorer larval survival, while on the other hand it showed that Artemia enrichment improved survival mainly under 'clear water' or low algal density condition. Meanwhile, increased algal density and Artemia enrichment were shown to significantly improve larval development and growth, respectively. The shortest mean development times to PL (20.5 and 21.5 days) were from both 10 x10⁶ cells ml⁻¹ treatments with enriched treatment having the shortest 20.5 days while non-enriched treatment at slightly longer 21.5 days. Meanwhile, all 'greenwater' treatments showed advanced 'Larval Stage Index' (LSI) compared with the 'clear water' treatments. In contrast, dry weights and total lengths of PL from enrichment treatments were heavier or larger. It is concluded that Artemia enrichment was most beneficial for larval culture when 'clearwater' method was used or microalgae was added at low concentrations in 'green water' culture.

Newly settled postlarvae (PL) of M. spinipes were stocked under three densities of 500 (low), 1000 (intermediate), 2000 PL m⁻³ (high) and with or without shelter, respectively to investigate the effects of stocking density and shelter as well as their potential interactions on the nursery culture of M. spinipes. Statistical analysis detected no significant interaction (P>0.05) between the two factors of stocking density and shelter within the range tested, the main effects were therefore analysed separately. With the survival results of the two treatments under a same density (i.e. with and without shelter) pooled, it showed that the low density (500 PL m⁻³) produced significantly higher mean survival (84.8 %) than the high density treatment (2000 PLm⁻³) (57.4 %) (P<0.05). The intermediate density (1000 PLm⁻³) generated an intermediate result (74.4 %), which was significantly different (P<0.05) from both the high and low density treatments. At the end of culture, the high stocking density also produced significantly heavier juveniles (wet weight: 144.24 ± 0.01 mg ind⁻¹), significantly higher final biomass (13.45 ± 1.39 g) and increase in biomass (8.87 ± 1.28 g) than that of the low density treatment (wet weight: 117.99 ± 0.003 mg ind⁻¹; final biomass: 4.69 ± 0.16 g and increase in biomass: 2.95 ± 0.15 g). Meanwhile, the addition of shelter produced significantly heavier juvenile wet weight (134.3 ± 0.01 vs. 123.61 ± 0.003 mg ind⁻¹) and higher final biomass (11.76 ± 1.84 vs. 8.79 ± 1.12 g). The results suggest that stocking density of 2000 PL m⁻³ improved final production while 500 PL m⁻³ improved survival. On the other hand, under the same stocking densities, shelter addition enhanced juvenile wet weight and final biomass.

In summary, the results of the present study suggest that the Australian native M. spinipes is a freshwater Macrobrachium species that shares many biological and aquaculture similarities with M. rosenbergii but also has some major differences. As it is native to Australia, M. spinipes has high potential for aquaculture in the country, therefore should be investigated further for its potential commercial farming in Australia and also possibly overseas.

Item ID:	46193
Item Type:	Thesis (Masters (Research))
Keywords:	algae; Australian strain; development and growth; effect of temperature; freshwater prawns; induced spawning; larvae; larval survival; Macrobrachium rosenbergii; Macrobrachium; microalgal concentration; Nannochloropsis sp.; prawn aquaculture; shrimp aquaculture; water quality
Related URLs:	http://researchonline.jcu.edu.au/7951/
Additional Information:	Publications arising from this thesis are available from the Related URLs field. The publications are: Chapter 3: Lober, Malwine, and Zeng, Chaoshu (2009) Effect of microalgae concentration on larval survival, development and growth of an Australian strain of giant freshwater prawn Macrobrachium rosenbergii. Aquaculture, 289 (1). pp. 95-100.
Date Deposited:	27 Oct 2016 03:53
FoR Codes:	07 AGRICULTURAL AND VETERINARY SCIENCES > 0704 Fisheries Sciences > 070401 Aquaculture @ 100%
SEO Codes:	83 ANIMAL PRODUCTION AND ANIMAL PRIMARY PRODUCTS > 8301 Fisheries - Aquaculture > 830105 Aquaculture Prawns @ 100%
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