Reproductive development and maturity stage benchmarking in a freshwater teleost ruffe Gymnocephalus cernuus L. in...

A wide range of classification schemes has been developed to describe reproductive development and stages in teleosts. These have been rationalised for clarity in recent years by Brown-Peterson et al. (Marine and Coastal Fisheries, 2011, 3, 52-70) and the WKASMSF (ICES, Report of the workshop for advancing sexual maturity staging in fish (WKASMSF), 2018) working groups. These have largely benchmarked classification schemes with examples from seawater fishes but have not been routinely applied to freshwater species. In addition, classification schemes developed to assess maturation of fish ovaries are either macroscopic and can be used in the field or histological for laboratory-based studies, and the two have rarely been coupled in the same classification scale or study. The present study reviews published maturation classifications for application to a freshwater teleost, ruffe Gymnocephalus cernuus L., sampled monthly over three annual cycles in Loch Lomond at locations in the extreme north and south ends of the loch. The gonado-somatic index and size frequency distribution of oocytes were used to verify the annual reproductive cycle and spawning of several egg batches. The study showed that a paired modified Percid scale (Treasurer & Holliday, Journal of Fish Biology, 1981, 18, 359-376) and the Rinchard scale (Rinchard & Kestemont, Journal of Fish Biology, 1996, 49, 883-894) gave an improved macroscopic and histological description of maturation compared with and benchmarked against previous ovarian developmental classifications for G. cernuus. The attributes of these various classifications are benchmarked and compared with the Brown-Peterson and WKMATCH scales, and the merits of these new notations are examined.