Líffræðifélag Íslands
Líffræðiráðstefnan 2015
Erindi/veggspjald / Talk/poster V41
Sigurvin Bjarnason (1,2), Jónas P. Jónasson (2), Guðrún Marteinsdóttir (1), Raouf Kilada (3)
1. University of Iceland, 2. Marine Research Institute of Iceland, 3. University of New Brunswick (Saint John), Canada.
Kynnir / Presenter: Sigurvin Bjarnason
Tengiliður / Corresponding author: Sigurvin Bjarnason (sigurvin@hafro.is)
A lack of extensive age information can lead to a poor understanding of life history and difficulty in estimation of parameters needed for modelling population dynamics. As with most crustaceans, Nephrops were thought to lose any calcified markings that could be used to determine age, during periodic molting. Recently, a direct method to determine the age of crustaceans was developed using growth band that are deposited on the eyestalk and/or the gastric mill ossicles as age indicator. The growth bands were found to be retained through different molting events. This study applied this novel direct age determination method on the Norway lobster, Nephrops norvegicus (Linnaeus, 1758) for the first time. Nephrops individuals were collected from two different Icelandic fishing grounds (Eldey and Breiðarmerkurdýpi). Consistent bands were observed in the zygocardiac ossicle of the gastric mill which were found superior to other ageing structures (i.e. other ossicles in the gastric mill and eyestalks). Site-specific estimated age-at-size curves were developed using growth band counts and they suggested a difference in growth rate between sites. Comparison between band counts and size-at-age interpretation determined from older length-frequency analysis differ slightly with increased variations for larger Norway lobsters. It is recommended that annual deposition of growth bands should be validated before implementing the technique into regular monitoring.