Age and growth of bogue, Boops boops, in Tunisian waters

The age and growth of bogue (Boops boops), collected in four areas off the Tunisian coast, were determined by studying growth marks on cross-sectioned otoliths. This calcified structure was chosen because the legibility and regularity of its growth mark patterns appeared to be more reliable than those of other skeletal elements. Opercula and fin rays were rejected because of intense bone remodeling, vertebrae because of numerous minute marks unrelated to cyclic events, and scales because counting of annuli seemed very unreliable, particularly in old specimens. Scales consistently had the highest average percent of error. Marginal zone analysis indicated that the hyaline zone in bogue otoliths was deposited yearly from November to April. Increase of length was determined and length-age data were fitted to Von BERTALANFFY equations. Comparisons of length increases of specimens from the four areas suggest two growth pools with greater increases in the north and east than in the Gulf of Tunis and the south. Relationships between growth and geographical distribution indicated the importance of environmental conditions especially water temperature and food availability, although the role of genetic and/or epigenetic factors could not be excluded.Original Abstract: Odredjivani su rast i starost bukve (Boops boops) na cetiri podrucja tuniske obale proucavanjem prstenova rasta na poprecnim presjecima otolita. Ova kalcificirana struktura bila je odabrana radi vece jasnoce i pravilnosti prstenova rasta nego na drugim skeletnim elementima. Skrzni poklopci i zbice peraja nisu bili uzeti u obzir radi intezivnog kostanog preoblicavanja, a vretenca radi brojnih znakova koji se ne odnose na ciklicke pojave. Ljuske nisu bile pogodne jer je brojanje prstenova bilo vrlo neprimjereno, narocito kod starih primjeraka. Za ljuske je srednji postotak pogresaka redovito bio najveci. Na rubnim dijelovima otolita bukve stvara se hialina zona svake godine od studenog do travnja. Prema Von BERTALANFFY-jevim jednadzbama odredjeni su porast duzine i odnos duzina-starost. Usporedbe duzinskog porasta ukazuju na veci porast primjeraka na sjeveru i istoku nego u Tuniskom zaljevu i na jugu. Odnosi izmedju rasta i geografske raspodjele naznacili su vaznost faktora sredine, narocito temperature i pristupacnosti hrane. Uloga genetskih i/ili epigenetskih faktora se takodjer ne moze iskljuciti.