Tuesday, 16 September 2014

Day 12- First fish weight sampling and aim of the project.

Sampling team working on platform (credits: Nicole Pelusio).

Today we sampled fish for one month growth trial in a commercial tilapia farm located on Volta Lake. 
The purpose of this trial is to compare the effects on growth performance rates on juvenile tilapia (Oreochromis niloticus) in cages on different rates of replacement of fish meal with Black Soldier Fly (Hermetia illucens) larval meal within the commercial diet of the fish. 

Tilapia (Oreochromis niloticus) juveniles (credits: Emilie Devic).

Because fish meal and fish oils are an increasingly expensive and unsustainable source of proteins for commercial tilapia feeds. Since this feed ingredient is taken from wild stocks, the continuing spread of aquaculture is pressing too much the demand, making its price raising and impoverishing the oceans. 
Moreover, there is still very little in the literature about comparing such feeds in tilapia culture in SS Africa or elsewhere.
With this trial we also want to   determine the economic viability of replacing certain percentage of fish meal with BSF meal in commercial tilapia feeds in Ghana.
Always concerning environmental sustainability, the dried BSF larval meal can be produced by recycling low value organic waste substrates (such as agriculture wastes and manure) into higher value protein sources through BSF production, with very low polluting impact (for example BSF production releases very low gases in the environment).

The trial consists of testing 4 different treatments (TO, T1, T2, T3): the control (T0) is a commercial diet used in commercial tilapia farms in Ghana. Those diets are supplied on demand for one month on 12 floating cages (1mt*1mt*1mt), where 6 gr tilapia juveniles are stocked in each.

The wooden platform (credits: Emilie Devic).


 In the morning a big wooden platform was pulled up next to the cages where the fish had fasted for at least 12 hours.

Fishing with bucket (credits Emilie Devic),

Tilapias were  netted out with a bucket, then counted in plastic baskets, dried the baskets, weighed them on a digital scales and recorded the number of fish and weight for gaining a weight average.

Counting tilapias in baskets (credits: Emilie Devic).

After sampling fish were put in few seconds in salted bath (30%) for avoiding pathogens spread after handling stress, and finally moved to each experimental cage.

Weighting dry basket with tilapias inside (credits: Nicole Pelusio).

Basket with counted and weighted fish going inside the cage after salt bath in a bowl (credits: Nicole Pelusio).

After sampling all the cages were properly labeled properly, recovered with anti-predators net and a shade for reduce stress.   
Labeling of cages (credits: Emilie Devic).

Anti-predators bed-net (credits: Emilie Devic).

Putting shading net (credits:Emilie Devic).
Cages sampled, labeled and covered after testing (credits: Emilie Devic).

The sampling started around 7,30 am and finished at 15,30 pm. In counting and fishing we were helped by a trained team of fish-farm led by supervisors Albert and Jemimah, whilst I and Emilie recorded the data. 

Sampling team in breack time waiting next samples (credits: Emilie Devic).



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