Interspecific Ecological Interactions of Invasive Janitor Fish (Hypostomus duodecimalis) and Kanduli (Arius manillensis)

Alien (non-native) organisms that have been introduced into a region outside of their natural range, established selfsustaining populations, and spread past their initial point of introduction are considered invasive species (Kolar and Lodge, 2010).
The rate of alien species introductions worldwide has accelerated due to factors such as increasing human population, expanding transportation capabilities, and economic globalization. Invasive fish species have also taken control of the waterways of the Philippines, causing harm to native fish in many ways, such as preying on native fish, outcompeting native fish for food or other resources, and preventing native fish from reproducing or killing young native fish (Baquiran, 2022). Gregory Paul "Gregg" H. Yan, founder of Best
Alternatives, has noticed a shift in the contents of fisherfolk's catch over the last ten years, with native fish like biya, ayungin, martiniko, ulang, and Kanduli becoming scarcer and alien species like Knifefish, Blackchin Tilapia, Cream Dory, and the
Janitor fish multiplying in inland waters (Lacsamana, 2021). This study investigated the ecological interactions happened between the Janitor fish, an invasive fish, and the Kanduli, a local fish in the Philippines. The Janitor fish (Hypostomus duodecimalis) from South America is an invasive fish species that is spreading in local waterways
and forests, threatening to edge out the country's indigenous plants and animals (Berame and Alfonso, 2019). It was originally introduced locally for aquariums, but careless handling and weak controls allowed it to escape into the wild. These
foreign species may look like cute fishes but government wildlife experts warn that they are displacing native fish while causing massive harm to the fishing industries (Macaraig, 2011). This study focused on predation and interspecific competition, as well as the growth rate and survival rate of the Kanduli that were made to interact with the Janitor fish. Data collection was conducted in one of the researcher's houses in Dagupan City during the second semester of 2022-2023 school year.