That's good to hear!
Sentience is the capacity to be aware of feelings and sensations.
Here's a video to save time: https://youtu.be/Ekd8YhNWBgg
But when you get a chance have a look through some of these:
Pain Perception in Fish Evidence and Implications for the Use of Fish https://www.researchgate.net/publication/286965130_Pain_Perception_in_Fish_Evidence_and_Implications_for_the_Use_of_Fish
Pain and Distress in Fish: A Review of the Evidence https://academic.oup.com/ilarjournal/article/50/4/327/868649
Fish Intelligence, Sentience and Ethics https://animalstudiesrepository.org/acwp_asie/75
Nocifensive behavior as evidence for sentient pain in fish https://www.wellbeingintlstudiesrepository.org/animsent/vol3/iss21/15/
Evoked potentials in the Atlantic cod following putatively innocuous and putatively noxious electrical stimulation: a minimally invasive approach https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3901938
Novel Candidate Genes Identified in the Brain during Nociception in Common Carp (Cyprinus carpio) and Rainbow Trout (Oncorhynchus mykiss) https://www.wellbeingintlstudiesrepository.org/acwp_vsm/25/
Mu Opioid Receptor from the Zebrafish Exhibits Functional Characteristics as Those of Mammalian Mu Opioid Receptor https://doi.org/10.1089%2Fzeb.2009.0594
A Novel Behavioral Fish Model of Nociception for Testing Analgesics https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4055884
Fish Analgesia: Pain, Stress, Fear Aversion, or Nociception? https://doi.org/10.1016%2Fj.cvex.2010.09.002
Time to (finally) acknowledge that fish have emotionality and pain https://www.wellbeingintlstudiesrepository.org/animsent/vol3/iss21/13/
Clinical Anesthesia and Analgesia in Fish https://doi.org/10.1053%2Fj.jepm.2011.11.009
The Evidence for Pain in Fish: The Use of Morphine as an Analgesic https://animalstudiesrepository.org/acwp_vsm/38
The dose–response relation for the antinociceptive effect of morphine in a fish, rainbow trout https://doi.org/10.1111%2Fj.1365-2885.2011.01363.x
Opioid Modulation of Pain Threshold in Fish https://doi.org/10.1023%2Fa%3A1026681519613
Avoidance learning in goldfish (Carassius auratus) and trout (Oncorhynchus mykiss) and implications for pain perception https://doi.org/10.1016%2Fj.applanim.2005.06.018
But what's more, some tests have even shown that fish are capable of self awareness. You might have heard of the mirror test. Some fish have been observed passing it: https://www.sciencedaily.com/releases/2019/02/190207142234.htm
Pain Perception in Fish Evidence and Implications for the Use of Fish https://www.researchgate.net/publication/286965130_Pain_Perception_in_Fish_Evidence_and_Implications_for_the_Use_of_Fish
Pain and Distress in Fish: A Review of the Evidence https://academic.oup.com/ilarjournal/article/50/4/327/868649
Fish Intelligence, Sentience and Ethics https://animalstudiesrepository.org/acwp_asie/75
Nocifensive behavior as evidence for sentient pain in fish https://www.wellbeingintlstudiesrepository.org/animsent/vol3/iss21/15/
Evoked potentials in the Atlantic cod following putatively innocuous and putatively noxious electrical stimulation: a minimally invasive approach https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3901938
Novel Candidate Genes Identified in the Brain during Nociception in Common Carp (Cyprinus carpio) and Rainbow Trout (Oncorhynchus mykiss) https://www.wellbeingintlstudiesrepository.org/acwp_vsm/25/
Mu Opioid Receptor from the Zebrafish Exhibits Functional Characteristics as Those of Mammalian Mu Opioid Receptor https://doi.org/10.1089%2Fzeb.2009.0594
A Novel Behavioral Fish Model of Nociception for Testing Analgesics https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4055884
Fish Analgesia: Pain, Stress, Fear Aversion, or Nociception? https://doi.org/10.1016%2Fj.cvex.2010.09.002
Time to (finally) acknowledge that fish have emotionality and pain https://www.wellbeingintlstudiesrepository.org/animsent/vol3/iss21/13/
Clinical Anesthesia and Analgesia in Fish https://doi.org/10.1053%2Fj.jepm.2011.11.009
The Evidence for Pain in Fish: The Use of Morphine as an Analgesic https://animalstudiesrepository.org/acwp_vsm/38
The dose–response relation for the antinociceptive effect of morphine in a fish, rainbow trout https://doi.org/10.1111%2Fj.1365-2885.2011.01363.x
Opioid Modulation of Pain Threshold in Fish https://doi.org/10.1023%2Fa%3A1026681519613
Avoidance learning in goldfish (Carassius auratus) and trout (Oncorhynchus mykiss) and implications for pain perception https://doi.org/10.1016%2Fj.applanim.2005.06.018
Self awareness in fish https://www.sciencedaily.com/releases/2019/02/190207142234.htm