Hot Weather And Poor Tilapia Egg Production

It is surprising that despite a major problem in Philippine aquaculture such as very low production of tilapia fry and fingerlings in the past months of March to July 2010, the people and government agencies involved in tilapia aquaculture have been silent about it.

Apparently, the El Nino effect has taken its toll on the tilapia industry.  There was minimal production of fry and fingerlings during these times such that its effect is felt now.  The price of table-sized tilapia has increased at a record-breaking high due to lack of supply.  The situation can worsen and will be felt in the months ahead until November or December since fry/fingerling production normalized only sometime in August when it started to rain.

It seems that this problem is not unique to the Philippines.  I am quoting here some posts from the tilapia@yahoogroups.com.  Perhaps, we can learn from their suggestions.

From:

david vance

Dear all,

I have some colleagues in Bangladesh who have a small tilapia hatchery, producing GIFT mono-sex tilapia. In July and August this year they had some problems with poor egg production, which they have said was due to high water temperatures. The high water temperatures were probably due to less than normal rainfall.

The water temperatures were apparently up to 33 degrees C.

I was wondering if this is a recognized problem with GIFT tilapia and if anybody else has strategies to overcome or minimize the problem. I assume that at higher temperatures it becomes even more important than usual to have good water quality.

Thanks for your time,

Dave

From:

ray dewandel

Dear Friends,

High water temps over 30C will lower reproduction in many ways.
Increased temp means higher oxygen demand and more stress from ammonia, pH, etc. Second, there have been studies which indicate that the milt is less motile and less eficient at higher temperatures. Maybe most importantly, every organism has an optimum temp. For nilotica it is genrerally 26-28 with variations according to strain and acclimation. Red Tilapia and Mossambicus strains generally have a higher optimum, say 28 to 30C.

Aeration especially to encourage evaporation and shading are two
methods to reduce temps. Also, deeper waters and plankton can provide more shade.

Mostly, here in the California desert, we simply shut down the hatchery
in the summer and wait for cooler temps. We often get the best production in January when the weather is coolest and the temps are 25 in the morning and 29 in the afternoon.

Ray DeWandel

From Dr. Jose Abucay

To all tilapia listers,

The problem of extreme temperature to tilapia spawning is probably a natural phenomenon the fish being a tropical fish. When temperature goes lower or higher than the required range the spawning success and efficiency is affected. In outdoor environment where the water condition is very dynamic and subject to many environmental factors there are many reasons why the fish stops or reduces spawning and has very low hatching rate. Most of the reasons were already pointed out by Ray deWandel but I would like to also share my views.

In the Philippines we also observed the same problem and it is really causing a big problem. During summer (April, May, June) when we have very minimal rain and the temperature is very high at daytime and very humid at nightime fingerling production is very low. When rainy season comes and farmers (particularly those depending on rain for their supply of water) begin stocking, the demand for fingerling is very high, but the supply is very low. Hence a solution to increase production during summer is highly needed.

Production of fingerlings peaks during the period of rainy season and fall during cold months and then rises again when temperatures increase. Looking at this trend, tilapia appears to love spawning when temperature is high at daytime and low at nightime but not when high at both day and night or low at both day and night.

My understanding of this phenomenon is that at continuous high temperature, especially at night time, the fish are subjected to continuous stress. Mouth incubating during this period is a disadvantage to the females  as she may need to gasp for air in the surface. And besides as mentioned by others the fertilization in tilapia being done externally the viability of the eggs and sperms can be affected when they are exposed to the extreme condition. At low temperature, water quality may be good, but the metabolic rate of the fish declines and possibly the viability of the eggs and sperms as well.

The key solution to this problem is simply to provide what the fish needs. We cannot force them to spawn if their environment does not excite nor permit them to spawn. So any activities that somewhat provide the condition may add some success like adding new and fresh water, providing artificial aeration specially during nighttime. Probably shading the pond to reduce temperature may help.

I am not into actual hatchery operation so I cannot comment on the business side whether doing these could be economical or not.  But this an example of a problem where it can probably be resolved by sharing our experiences and observations, specially the farmers. We on the academic and research side can explain the science behind problems but we need actual data and observations.

May the hatchery operators please react and share your views.

Jose S. Abucay
College of Fisheries
Freshwater Aquaculture Center
Central Luzon State University
Science City of Munoz, Nueca Ecija Philippines

From: jobaldia 


Hi:

In my several years of operating a commercial tilapia hatchery here in the 
Philippines, this year was exceptionally problematic due to the prolonged dry 
season which started in Feb and lasted till July. As a result, there was 
absolutely minimal tilapia fry and fingerling production during that time making 
the current price of the table sized tilapia at record breaking high due to lack 
of supply.

Based on the temperature recorded, ambient temperature reached as high as 38C, but this is not unusual because we have had this high temp at the peaks of 
summer before. Perhaps, this was aggravated by the lack of water in the 
irrigation canals and low water table for those using shallow well pumps due to the El Nino phenomenon.

I have tried to solve this problem in our farm by 1) increasing the water level 
of the fishpond to from 1m to 1.5 m. High level of water serves as a buffer 
that minimizes large fluctuations in temperature. This is based on the premise 
that big volumes of water takes longer to "boil" than smaller volumes. 2) more 
frequent water changes from the shallow well. We certainly had higher fuel 
expense but we still managed to have some sales. Our production was still 
relatively low during that time but not like others who have zero fingerling 
output.

I find shading as recommended quite impractical in my case due to the large area involved. Also, I could not imagine how growing algae can significantly reduce the temperature of the water.

I find the recommendation of moving to another location with high altitude 
funny.

Jojo