Miss Sherilyn Abarra

Miss Sherilyn Abarra

School of Biological and Marine Sciences (Faculty of Science and Engineering)



PhD student - Biological Sciences

Project Title: Dietary Supplementation of Host-derived Probiotics and its Effects on the Growth Performance, Feed Utilization, Intestinal Histology, and Digestive Enzymes of Tilapia and Carp

Director of Studies: Dr Daniel Merrifield

2nd Supervisor: Dr Mark Rawling

My PhD project investigates on the effects of potential host-derived probiotics on growth, feed utilization, intestinal health, and digestive enzymes of tilapia and carp. Probiotics derived from the host have gained attention for its suitability and capacity to establish effective colonisation of the host gut. Autochthonous probiotic candidate isolates from mirror carp and Nile tilapia will be screened in vitro for pathogen antagonism activity, pathogen-mucosal colonisation studies, and extracellular enzyme activity. The potential probiotic candidates will be tested for antagonism against important fish pathogens such as Aeromonas hydrophila, Streptococcus iniae, Vibrio anguillarum, Yersinia ruckeri, and Pseudomonas anguilliseptica. Promising candidate isolates will be selected for use in pathogen-mucosal colonisation studies on a range of aquacultured freshwater fish species. This assay will be conducted to investigate the potential of the probiotic candidate isolates to inhibit the proliferation of the fish pathogen in the rearing medium and on the mucosal surfaces of the fish. To perform this, the fish will be euthanized and exposure assays will be conducted using whole fish bodies immediately post-mortem. This is a pilot approach to reduce the negative impacts on welfare by challenging live fish. The potential candidate isolates will also be subjected to qualitative screening for phytase, xylanase, tannase, and chitinase production. 

Potential probiotic candidates from the in vitro assays will be incorporated in the fish diets to be used for in vivo studies. In vivo trials will be conducted to assess the effects of the probiotic diets on fish growth performance and carcass composition. Fish intestinal samples will be processed for histological examination, microbiological analysis, and gene expression analysis to assess wider impacts of the probiotic diets on gut health status.


  • Master of Science in Biology (MS Biology), Ateneo de Manila University Loyola Schools
  • Bachelor of Secondary Education (BSEd) - Major in Biological Science, Laguna State Polytechnic University

Professional membership

  • World Aquaculture Society
  • Global Aquaculture Alliance

Roles on external bodies

  • External Reviewer - Sinaya Journal



Research interests

  • fish nutrition
  • functional feed additives 
  • sustainable aquaculture

Grants & contracts

  • Scholarship Recipient - Department of Science and Technology-Science Education Institute (DOST-SEI) Foreign Graduate Scholarship in Priority Science and Technology Fields
  • Scholarship Recipient - Accelerated Science and Technology Human Resource Development Program (ASTHRDP), DOST-SEI
  • Research Grant - DOST Student Research Support Fund




Abarra, S. T., Velasquez, S. F., Guzman, K. D. D. C., Felipe, J. L. F., Tayamen, M. M., & Ragaza, J. A. (2017). Replacement of fishmeal with processed meal from knife fish Chitala ornata in diets of juvenile Nile tilapia Oreochromis niloticus. Aquaculture Reports, 5, 76–83. https://doi.org/10.1016/j.aqrep.2017.01.001

Presentations and posters

April 7, 2016 - Poster Presentation; Knife fish (Chitala ornata) meal as fishmeal replacement in diets of Nile tilapia (Oreochromis niloticus), 1st DOST-SEI ASTHRDP-NSC Scholar's Conference -Philippine International Convention Center (PICC), Manila 

May 27, 2016 - Oral Presentation; Knife fish (Chitala ornata) meal as fishmeal replacement in diets of Nile tilapia (Oreochromis niloticus), 7th World Fisheries Congress -Busan, South Korea