Age, growth and population structure of Modiolus barbatus from the Adriatic
- 254 Downloads
Age, growth and population structure of Modiolus barbatus from Mali Ston Bay, Croatia were determined using modal size (age) classes in length frequency distributions, annual pallial line scars on the inner shell surface, internal annual growth lines in shell sections of the middle nacreous layer and Calcein marked and transplanted mussels. The length frequency distributions indicated that M. barbatus attain a length of ∼40 mm in 5–6 years indicating that a large proportion of the population in Mali Ston Bay is <5 years old. Some mussels of ∼60 mm were predicted to be 14 years old using the Von Bertalanffy growth (VBG) equation. Up to the first 6 pallial line scars were visible in young (<6 years) mussels but in older shells the first scars became obscured by nacre deposition as the mussel increased in length and age. The age of the older shells (>6 years) was determined from the middle nacreous lines in shell section, which formed annually in winter between February and March; the wider dark increments forming during summer (June to September). The oldest mussel, determined from the middle nacreous lines, was >12 years, with the majority of mussels aged between 3 and 6 years of age. The ages of mussels ascertained using the growth lines were not dissimilar to the ages predicted from the length frequency distributions. Age at length curves produced using modal size class data were not different from the data obtained using the pallial scar rings and internal growth lines. Taken together these data suggest that M. barbatus attains a length of 40 and 50 mm within 5 and 8 years, respectively. Eighty one percent of individual M. barbatus injected with a Calcein seawater solution (300 mg Calcein l−1), into their mantle cavity successfully deposited a fluorescent line, which was visible in suitably prepared shell sections under ultra violet light. Incorporation of Calcein into the mussel shells was seasonally variable with the lowest frequency of incorporation in mussels marked in February and recovered in May. Seasonal shell growth was observed with significantly higher growth rates in mussels marked in May and removed in August (ANCOVA, F3,149 = 23.11, P < 0.001). Mussels (∼18 to 22 mm) marked in May and recovered in August displayed maximal growth rates of >2.5 mm month−1 compared with a mean mussel growth rate of 1.2 ± 0.6 mm month−1. At other times of the year mussel shell growth ranged from immeasurable to 1.48 mm month−1.
KeywordsCalcein Growth Line Shell Growth Mussel Shell Length Frequency Distribution
This research was financed by the Croatian Ministry of Science and Technology. The authors are grateful to Željko Baće, Marko Žarić, Nika Stragličić, Lovorka Kekez and Mark Prime for technical assistance. Special thanks to Barbara Zorica for help with statistical analysis and Professor C.D. McQuaid for helpful suggestions for Calcein marking the mussel shells. The experiments conducted comply with the current laws of Republic of Croatia.
- Benović A (1997) The history, present condition, and future of the molluscan fisheries of Croatia. In: MacKenzie CL Jr, Burrell VG Jr, Rosenfield A, Hobart WL (eds) The history, present condition, and future of the molluscan fisheries of north and Central America and Europe, vol 3, Europe. NOAA Technical Report NMFS 129. US Department of Commerce, pp 217–226Google Scholar
- Gaspar MB, Richardson CA, Monteiro CA (1994) The effects of dredging on shell formation in the razor clam, Ensis siliqua from Barrinha, southern Portugal. J Mar Biol Assoc UK 74:927–938Google Scholar
- Gosling E (2003) Bivalve mollusks—biology, ecology and culture. Fishing news books, OxfordGoogle Scholar
- Mladineo I, Peharda M, Orhanović S, Bolotin J, Pavela-Vrančić M, Treursić B (2007) The reproductive cycle, condition index and biochemical composition of Modiolus barbatus. Helgoland Mar Res (submitted)Google Scholar
- Morton B (1977) The biology and functional mortality of Modiolus metcalfei (Bivalvia, Mytilacea) from the Singapore mangrove. Malacologia 16:501–517Google Scholar
- Poppe GT, Goto Y (2000) European seashells, vol II (Scaphopoda, Bivalvia, Cephalopoda), 2nd edn. ConchBooks, Hackenheim GermanyGoogle Scholar
- Ramsy K, Richardson CA (2000) Techniques for assessing repaired shell damage in dog cockles, Glycymeris glycymeris L. J Shellfish Res 19:927–931Google Scholar
- Richardson CA (2001) Molluscs as archives of environmental change. Oceanogr Mar Biol Ann Rev 39:103–164Google Scholar
- Sparre P, Venema SC (1992) Introduction to tropical fish stock assessment. Part 1, Manual. FAO Fish Tech Pap (Revision 1) RomeGoogle Scholar
- Zavodnik D (1997) Non-conventional seafood sources at the eastern Adriatic sea markets. In: Finka B (ed) Thousand years from first mention of fisheries in Croats (in Croatian). Croatian Academy of Arts and Sciences, Zagreb, pp 637–656Google Scholar