From Longman Dictionary of Contemporary Englishtiddlertid‧dler /ˈtɪdlə $ -ər/ noun [countable] British English informalHBF a very small fish
Examples from the Corpus
tiddler• His tongue regularly darted out of his mouth and flicked this way and that along his lips like a tiddler under water.• The tiddlers of the aerospace world are also expanding.• If they were tiddlers he always threw them back. 