Interspecific Ecological Interactions of Invasive Janitor Fish (Hypostomus duodecimalis) and Kanduli (Arius manillensis)
Description
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.
Files
Steps to reproduce
This research used quasiexperimental research design and narrative observation to observe the H. duodecimalis and A. manillensis in a simulated environment. The characteristics of the experimental group population was studied based on growth rate and survival rate. The researchers used two fish tanks with H. duodecimalis and A. manillensis in one tank and another tank with A. manillensis only. They caught 10 Janitor fish and 20 A. manillensis and raised them in a recirculating aquarium. The researchers fed them plants and vegetables two to three times daily. Data gathering measure size, interspecific ecological interactions, and survival rate. Growth rate and survival rate were used to determine effects of invasive Janitor fish on Kanduli fish. Additionally, the researchers also used tape measure and weighing scale to determine the length and weight of the experimental and control group before and after the experiment. Narrative observation was also used to record interspecific ecological interactions happened between the two fish species. The researchers observed predation and interspecific competition between H. duodecimalis and A. manillensis in their aquarium. The researchers also computed for average growth rate, the formula used was, Growth rate (length/weight) = Log of final weight or length - Log of initial weight or length/no. of days*100 and for the survival rate, Survival Rate = no. of Kanduli alive/no. of Kanduli living from the start*100 The researchers based on these formulas to determine the characteristics of the A. manillensis population after the experiment. To determine if there is a statistically significant difference between the A. manillensis population that were made to interact with the H. duodecimalis and those that were not in terms of growth rate and survival rate, the null hypotheses per variables of interest were tested using independent sample t-test.