In this study, we investigate the role of environmental enrichment and tryptophan supplementation in increasing animal welfare indices in tilapia. To do this, the environment where fish are reared is enriched using artificial aquatic plants and shelters, and their diet is supplemented with tryptophan. Animal welfare parameters are estimated and compared to verify this enrichment.3
Agonistic encounters between tilapia interacting with one another inside the same aquarium tank are quantified in two ways: (a) the total number of aggression-associated confrontations; and (b) the quantified escalations of aggressive confrontations—i.e., intimidating threats met with evasive fleeing, versus high-risk confrontation where aggression escalates to physical contact, leading to injuries or death.3
Having shelter-like structures like fake coral or rocks and/or fake aquatic plants tends to deter agonistic encounters, especially confrontations which involve physical violence between tilapia forced to share the aquarium tank.2,3 This conclusion wasn’t only verified by counting agonistic encounters between fish, and by ranking the severity of those encounters, the overall welfare of the aquaculture-raised fish could also be measured in weight gain comparisons—surely an important feature for marketable tilapia.
Fish in shelter enrichment presented improved weight gain. Treatment with artificial water hyacinth presented the best and most consistent results in tilapia stress parameter.3
The investigation was conducted by the aquaculture sector of the Faculty of Veterinary Medicine and Animal Science at São Paulo State University (Universidade Estadual Paulista, “UNESP”). The research team used 640 juvenile Nile tilapia males.2,3
Polyvinyl chloride (PVC) pipes were used for shelter-like structures. Fake water hyacinth plants were fabricated using frayed nylon and Styrofoam.3 Another aspect of the experimental study involved providing tryptophan, the so-called “Thanksgiving turkey amino acid,” as a dietary supplement. One group of tilapia—the control set—had none of these extra features in their habitat.4
The first [experimental] treatment was composed of environmental enrichment, using PVC pipes, 10 cm in diameter and 20 cm in length, for shelter. The second used artificial water hyacinths (frayed nylon rope simulating the natural water hyacinth root) fixed to Styrofoam structures or to the aquarium itself. The third treatment was outlined with food supplementation with the amino acid tryptophan supplemented to the diet at 2.56 percent by weight. The fourth treatment was a control tank without enrichment or supplemented food.2
Unsurprisingly, like Americans after a high-tryptophan meal (such as feasting on turkey),5 the tryptophan-diet-enriched tilapia demonstrated less aggression.2
An analysis of aggressive behaviour showed lower numbers of confrontations in the tanks where the food had been supplemented with tryptophan food-supplemented treatment compared to the control and environmental enriched treatments. This is because it is a serotonin precursor, a neurotransmitter involved in the control of aggressive behaviour and the susceptibility to stress.2
Ironically, the introduction of the fake plants and shelter-like structures weren’t the true peace-making modification of the habitats. Rather, tilapia recognized these features as new “turf” to be valued and used for establishing individual territories—turf worth competing for. Near these extra environmental enhancements, tougher tilapia scared off weaker fish, such that these value-added extras were secured by threats, usually without physical contact, so that territories were defined and respected.
On the other hand, water hyacinth and shelter presented high levels of confrontation. “Despite the benefits, enriched environments can generate competition between territorial fish, which means more confrontations,” the researchers noted.2
But this increase in low-level confrontations—which quickly led to established property boundaries—actually benefitted the group because these territory showdowns were quickly resolved apart from physical violence that often accompany competing males in unstructured open-water confinements.
However, they also noted that environments enriched with artificial water hyacinth and shelters led to less intense confrontations, which were mostly threats rather than fighting, and concentrated at the section with enrichment items. In the control situation the occurrence of these confrontations were more intense – leading to pursuits, lateral confrontation, and bites – and occurred through the entire aquarium region.2
The study provided some easy-to-recognize lessons about improving life for Nile tilapia. In sum, the research team concluded that fish-farming operations can improve the health and welfare of their aquaculture stock by applying inexpensive features that mimic natural habitat, i.e., equipping the confinements with structures that tilapia can use to reduce high-risk agonistic encounters, as the tilapias define territorial boundaries.2,3
[Thus,] a poor environment in fish farming has deficiencies that can be improved by including proposed enrichments, filling a fish need to express natural behavior, improving the quality of life for animals. We can highlight artificial water hyacinths as the treatment that presented the best and most consistent results. Such a means of environmental enrichment can be easily implemented in fish farms since it is low cost, easy to handle, and highly durable.”3
Providing nature-like structures within artificial aquatic habitats makes it easier for fish to establish their own territorial spaces. With space allocated among individual fish, which they signal as “taken,” boundaries reduce high-risk aggressions based upon multiple claimants to the same space.6
Accordingly, Nile tilapia live better, engage in less high-risk competitive aggressions among themselves, and grow healthier and larger, if their physical environment is made more like the natural habitat that God providentially fitted them for—and that’s no surprise to Genesis-affirming creationists.
1. The Norwegian salmon-farming industry launched with the practice of using floating netpens (or net-cages) in coastal ocean-waters, growing quickly into global operations copied by aquaculture operations round the world. Johnson, J. J. S. Nordic Salmon Farming: Responding to the Genesis Mandate,” Nordic Legacy Series. Fort Worth Texas: Norwegian Society of Texas, April 26, 2015. See also Johnson, J. J. S. 2013. Fulfilling the Genesis Mandate while Helping the Poor. Acts & Facts. 42 (12): 19.
2. See Fletcher, R. 2020. Fake Plants Have Real Benefits for Farmed Tilapia. The Fish Site. Posted at thefishsite.com on June 18, 2020, accessed June 20, 2020.
3. Neto, J. F., and P. C. Giaquinto. Environmental Enrichment Techniques and Tryptophan Supplementation Used to Improve the Quality of Life and Animal Welfare of Nile Tilapia. Aquaculture Reports. July 2020, volume 71, article 100354.
4. Steves, J. 2013. Tilapia Project Helping African Community. Cooke Aquaculture Newsletter. Spring-summer issue, 4-5. The Nile tilapia (Oreochromis niloticus) is a cichlid fish native to north Africa and Israel, now fish-farmed and marketed worldwide, especially in China. Nico, L. G., P. J. Schofield, and M. E. Neilson. 2019. Oreochromis niloticus (Linnaeus, 1758). Fishery Cultured Species. Posted on fao.org on June 22, 2020, accessed on June 23, 2020.
5. Staff writer. 2014. Turkey Coma? That’s a Fact. Posted at vimeo.com.
6. See James 3:16. Strife often occurs when multiple claimants seek to have the same thing. Accordingly, agreed-upon boundaries benefit everyone.
*Dr. Johnson is Associate Professor of Apologetics and Chief Academic Officer at the Institute for Creation Research.