1. ACKNOWLEDGEMENTS
This project was made possible by all the hard
work of Cindy Staicer and Martha Mullally of the
Dalhousie Integrated Science Program.
Additionally we’d like to thank the shareholders
and staff of NovaEel for funding the project.
REFERENCES
Yoshikawa M. 2013. Sex differences in growth rates of
early life stage Japanese eels Anguilla japonica
under experimental conditions. J Fish Biol. 83(3): 588-97.
Tzchori I, Degani G, Elisha R, Eliyahu R, Hurvitz A, Vaya J,
Moav B. 2004. The influence of
phytoestrogens and oestradiol-17β on growth and sex
determination in the European eel
(Anguilla anguilla). Aquac Res. 35(13): 1213-19.
INTRODUCTION
This study compared the palatability of different food types for Anguilla rostrata (American eel). Female eels grow to a larger average size
than male eels, so a common practice in aquaculture is to feminize the eels using a feminizing agent which changes the type of feed preferred by
the eels. The treatments tested were Mazola corn oil, 0.5% haddock roe, 1.0% haddock roe, and 0.2% betaine. None of the treatment feeds had
an increased palatability above the feminizing feed; However, the betaine resulted in the most eel growth per gram of feed consumed. Aspects of
competition and behavior were also observed to explore the possibility of skewed data. This research is important in developing the field of eel
aquaculture in Canada and increasing the value of the industry.
0.00
5.00
10.00
15.00
20.00
25.00
Control (-) Control (+) Treatment
RatioBetweenGramsofFood
ConsumedandGramsofGrowth
Feed Type
RESULTS
+ Control
+ Control
Treatment
Treatment
- Control
- Control
0 10 20 30 40
With Food Present
Without Food Present
% of Eels in the Designated Feeding Area ( %N )
TypeofFeedWithandWithoutFoodin
theTanks
0 20 40 60 80
Control (+)
Treatment
Control (-)
% Of Feed Consumed
TypeofFeed
ABSTRACT
• In American eel (Anguilla rostrata)
aquaculture conditions there tends to be a
higher percentage of males than females
(Yoshikawa 2013)
• Female American eels grow to a larger size
than males having a higher global market
value (Tzchori et al. 2004)
• To have a higher economical product value we
treat the eels with a feminization agent infused
into the feed
• After feminization period the eels develop a
change in palatability showing an aversion to
the regular feed
• Therefore, it is important to develop a new diet
that is palatable to the eels
HYPOTHESIS:
The treatment feed will increase consumption
and growth of the eels in an aquaculture
environment more efficiently than regular or
hormone induced feed and that the eels will
show preference towards the betaine feed
METHODS
• The smallest amount of error in wet and dry
weight for the feed is after absorbing water for
45 minutes
• The feeding trials took place in nine separate
tanks, each with the same approximate
weight of eels
• Three tanks were fed negative control
(regular feed), three tanks positive control
(feminization feed), three tanks treatment
feed (lipids, 0.5%/1.0% roe protein, betaine)
• The feed was in the tanks for 45 minutes then
leftover feed was collected in a net as the
tank drained
• The wet food collected was weighed, dried for
72 hours, then weighed again to obtain the
dry weight
FEED TRIALS
BEHAVIOUR TRIALS
• The tanks were exposed to low light for 30
minutes before filming
• Each tank was filmed for five minutes with a
DSLR camera, without feed and during
feeding
• The film was paused every 15 seconds and
the number of eels present in the feeding
zone were counted
• Using the total number of eels in the tank,
the percentage of eels in the feeding zone
was calculated for the feeding time
• There was a significant difference between
the lipid and the roe trials
• Evidence to support a higher palatability for
roe
• However, there was no significant
difference between the roe feed and the
control feeds (p>0.05)
• The growth of the eels was insignificant
between trials
FEED RESULTS: ROE AND LIPIDS
0
0.5
1
1.5
2
2.5
3
3.5
4
Empty Regular Oil 0.5%
Haddock Roe
1% Haddock
Roe
AverageFeedReturn
Treatment Type
Positive Control
Negative Control
Treatment
FEED RESULTS: BETAINE
BEHAVIOR RESULTS: BETAINE
• Eels eating the
betaine treatment
grew the most
(slightly more than
the positive control,
significantly more
than negative
control)
• The eels that were
fed betaine had
significantly higher
difference in grams
of feed consumed/
grams of growth
• Betaine consumed
was less than
positive control
• The percentage of the population
located in the feeding area with and
without feed in the tank for betaine was
significantly higher than the negative
control
• It was not significant when compared to
the positive control
• The photo on the right
depicts the end of a
smaller eel’s tail that
had been partially
digested by a larger eel
DISCUSSION
CONCLUSION
• Out of all three treatment
feeds, the eels consuming
the betaine grew the most
per gram of feed consumed
• The roe and lipid feed did
not have a significant
difference when compared to the controls
• When compared to each other there was a
preference to the roe over the lipids
• Betaine treatment was found to be preferred
significantly to the negative control feed and
preferred almost equally to the positive
control
• The data suggests that eels are eating less
food and growing more when fed betaine,
which is economically beneficial in terms of
most efficient growth for lowest cost of food.
• Competition is one of
the major errors that
could have skewed
the data in this
experiment because it
has been known to be
a feeding deterrent
• We would like to use the filming of eels as
a way to measure effects of competition in
aquaculture
• We would also like to explore the effects
of carbohydrates as a treatment feed or
possibly nitrogen infused feed
ERRORS
FUTURE WORKS
• Betaine is the most
viable substitute for the
feminization feed out of
all of the treatments
and the controls
• The lipids decreased
the weight of the eels,
while the proteins had
no significant effect on
their growth