Evaluation of finrays as a non-lethal ageing method for protected goliath grouper Epinephelus itajara

Abstract

Currently, there is a conflict between the need to conserve protected fish species and the need to use lethal methods to collect essential biological data, such as age, to assess their population status and recovery trends. We evaluated the precision and accuracy of a non-lethal ageing method for goliath grouper Epinephelus itajara, listed as critically endangered on the IUCN Red List of Threatened Species. Paired finray and otolith samples (n = 21) were collected opportunistically from fish that had died primarily from red tide or hypothermal events in Florida coastal waters. Finray ageing proved relatively precise (coefficient of variation [CV] = 4.24%), although less so than otolith ageing (CV = 1.45%). Finray ages agreed with otolith ages the majority of the time (CV = 3.15% and concordance correlation coefficient = 0.991) for E. itajara from 0 to 18 yr of age. Based on a test of symmetry, finray ageing was also relatively unbiased for fish up to 18 yr of age. Further evaluation of any limitations of the method will depend on obtaining more samples, especially from larger, presumably older, fish. Clearly, the non-lethal finray ageing method can be used as an alternative to using otoliths for goliath grouper at least up to 18 yr of age. Finray ageing could significantly reduce the need to sacrifice protected E. itajara to assess their population recovery. KEY WORDS: Epinephelus itajara · Goliath grouper · Otoliths · Finrays · Non-lethal ageing · Florida Resale or republication not permitted without written consent of the publisher OPEN PEN ACCESS CCESS Contribution to the Theme Section 'Range-wide status and conservation of the goliath grouper'Endang Species Res 7: 213-220, 2009 their original distribution range throughout southwest Florida and the Florida Keys, while the frequency of adult sightings has increased in offshore artificial structures of southwestern Florida (Cass-Calay & Schmidt 2003, Porch & Eklund 2003, Frias-Torres 2006, NMFS 2006. This apparent population increase has generated requests by fishermen to re-open the fishery in Florida.Assessing the population status of both juvenile and adult goliath grouper is critical for addressing these over-exploitation and recovery issues (Kingsley 2004). Obtaining biological data is essential for estimating population parameters (i.e. growth, age-specific reproductive potential, recruitment, and mortality rates; Haddon 2001) that are used as input to stock assessments to predict recovery trajectories. The problem faced by management agencies is how best to obtain the data required for stock assessment without jeopardizing the very population they are trying to protect. The crux of the problem is that most bony fishes are aged by using their sagittal otoliths, which requires killing the fish. Ageing goliath grouper with this method is clearly inconsistent with the goal of conserving the species. Non-lethal ageing methods present a viable alternative, in which dorsal or pectoral finrays can be removed from live fish, which are subsequently re...

Identification of a nonlethal method for aging tautog (Tautoga onitis)

“…Scales have been a primary structure for nonlethal age determination in many other fish species (e.g., Penttila and Dery, 1988;Welch et al, 1993;Secor et al, 1995;Elzey et al 4 ), but our data support the find- Table 1 Average age and sample size for each type of structure examined for each final age assigned for tautog (Tautoga onitis) collected in Buzzards Bay, Massachusetts, in 2014. Final ages were assigned by 2 age readers taking into account ages assigned, and quality of all structures examined for each fish.…”

“…In comparisons of otoliths, dorsal-fin spines, and teeth of the leopard coralgrouper (Plectropomus leopardus), Hobbs et al (2014) found that the most cost-and time-efficient structure for age determination was the dorsal-fin spine. Fin rays or spines also have been found to be useful by Sylvester and Berry (2006) Murie et al (2009) …”

Non-lethal age determination for juvenile goliath grouper Epinephelus itajara from southwest Florida

“…These factors, along with the fact that goliath grouper approaching 6 yr of age and 1 m in length migrate out of the current study area, inhibited our attempts to obtain samples from fish in this size/age category. A study exploring the use of dorsal fin-rays for ageing adult goliath grouper appears in this Theme Section (Murie et al 2009). Studies assessing the utility of fin-rays for ageing other groupers such as gag Mycteroperca microlepis and Nassau grouper Epinephelus striatus are in process (D. J. Murie pers.…”

Age, growth, and mortality of the Atlantic goliath grouper Epinephelus itajara in French Guiana

“…The disadvantage of using otoliths to age a fish is that it is a lethal method that is not appropriate for critically endangered species. Fortunately, a non-lethal method of aging goliath grouper has been developed using dorsal fin rays (Murie et al 2009). Ages of goliath grouper using otoliths and fin rays from the same individuals were found to be comparable to the age of 18 yr (older individuals were not available) for fish sampled off the east coast of Florida (Murie et al 2009).…”

“…Fortunately, a non-lethal method of aging goliath grouper has been developed using dorsal fin rays (Murie et al 2009). Ages of goliath grouper using otoliths and fin rays from the same individuals were found to be comparable to the age of 18 yr (older individuals were not available) for fish sampled off the east coast of Florida (Murie et al 2009). However, the ability to apply this methodology to age goliath grouper using fin rays or otoliths in French Guiana was uncertain at the outset of this project because of the region's equatorial location, where the seasonal variation is usually minimal and hence the annuli in the aging structures may be indiscernible.…”