Abstract
The common carp Cyprinus carpio is one of the most widely-distributed freshwater fishes in the world. Due to its value for conservation and fisheries in several native/translocated areas of distribution and its detrimental effects on the aquatic ecosystem in most invasive areas, robust age-based population dynamics models are required for successful management of this species. The present study provides a global review of age determination in carp, including a historical account of ageing methods, an assessment of the relative utility of ageing structures, and an evaluation of precision and accuracy (i.e. validation) of age estimates. Historically, scales were by far the most widely-employed structure, followed by the operculum, otolith, dorsal spine, vertebra and fin ray. However, in countries where carp is categorised as ‘high risk’ of impact, use of alternative structures to the scale was predominant. Causal criteria analysis showed scales and opercula to provide inconsistent evidence for successful annulus identification/counting, whereas consistent evidence was found for otoliths, dorsal spines, vertebrae and (pectoral) fin rays. Precision was always above reference thresholds for scales, whereas for otoliths, dorsal spines and fin rays was in several cases below. Accuracy was addressed sporadically and mostly in high-risk countries. It is suggested that dorsal spines or pectoral fin rays should be used in lieu of scales as non-lethal ageing structures, and otoliths (or vertebrae, pending more research) otherwise, and that validation should always be attempted as part of the set-up of more appropriate ageing protocols and use of correct terminology.
Highlights
Age determination in fish is fundamental for the management of fisheries (e.g. Hilborn and Walters 2013) and for understanding species’ life histories and their population dynamics (Beddington and Kirkwood 2005)
Use of opercula and dorsal spines started in the 1950s, of vertebrae in the 1960s, of otoliths in the 1980s, and of fin rays in the 1990s
Insufficient evidence 1 out of four) and the fin ray; and below 7.6% for the coefficient of variation (CV) were achieved for the operculum, the otolith, and the dorsal spine—noting that in the latter case all four studies assessing between-interpreter precision by the CV fell below the desirable levels of precision
Summary
Age determination in fish is fundamental for the management of fisheries (e.g. Hilborn and Walters 2013) and for understanding species’ life histories and their population dynamics (Beddington and Kirkwood 2005). Age determination typically involves the counting of annual (or daily) increments under the assumption that these were formed on an equivalent temporal interval. This assumption is verified through validation, which is equivalent to determining the accuracy of an age estimate (Campana 2001). Failure to accomplish the aforementioned accuracy–precision requirements is likely to result in erroneous age estimates. This leads to biased understanding of fish population dynamics, with consequences for the management and conservation of species The importance of age validation (cf. Beamish and McFarlane 1983) for fish and fisheries biologists (sensu Balon 1999), including the set-up of so-called ‘production ageing’ programmes (i.e. reference collections of ageing structures and quality control monitoring), which have become an intrinsic component of modern fisheries laboratories in many parts of the world (Campana 2001)
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