Leptocephalus of Conger in the Firth of Clyde

Growth-rings on the shell of the scallop (Pecten maximus) are laid down annually, in spring, and so can be used to determine the age.Scallops grow from spring to December, and cease growing in winter. The resumption of growth in the spring is marked by the appearance of the annual growth-ring at the edge of the shell.The first year's growth is of one of two types. A few scallops have shells which show a large first year's growth, 28 mm or more wide, while the great majority have shells which show a small first year's growth, less than 28 mm wide. These two types probably depend on the two principal spawning periods of the scallop, most of the former arising from the spring spawning and most of the latter from the autumn one.The growth curve of P. maximus is of a type characteristic of lamellibranch shells. The annual growth is greatest in the first two or three years of life, after which it decreases steadily.Scallops grow more quickly in shallow water than in deeper water.Possible causes of the annual cessation of growth are discussed.A paucity of young scallops was noted in the dredge samples, as previous workers have reported. No reason can be given.

Section: The Annual Period Of Growthmentioning

confidence: 82%

Section: He Growth-ringsmentioning

confidence: 99%

The age and growth of the scallop, Pecten maximus (L.), in Manx waters

Mason

1957

“…There is therefore little information on their biology from the time of settlement to the end of their first year. Attachment has been observed to rhodophytes (Mason, 1957;Le Pennec, 1974), phaeophytes (Elmhirst, 1945;Mason, 1958Mason, ,1983Minchin, 1981), hydroids (Dare, personal communication; Round et ah, 1961;Eggleston, 1962), bryozoa, tubiferous annelids (Eggleston, 1962), and shell gravels (Le Pennec, 1974). Detection of areas where spat settle in abundance is important in the management of wild scallop fisheries and aquaculture.…”

Section: Introductionmentioning

confidence: 99%

Biological observations on young scallops, Pecten maximus

Minchin¹

1992

The biology of young scallops Pecten maximus (Mollusca: Bivalvia) was examined using SCUBA diving. Within shallow and sheltered bays settlement took place near adult populations. Surfaces to which scallops attached were generally free of silt; these included algae, invertebrate tests and inorganic materials. Detachment could take place amongst individuals of 1 mm; however, in sheltered bays most remained attached until 4–13 mm. Following detachment scallops recessed in sediment. They were subject to dispersal by water turbulence and swimming induced by sea-stars. There was evidence to suggest high mortality from crab and sea-star predation during the summer and autumn.

“…The September peak would be expected to be much higher than the April peak, owing to the much greater amount of spawn shed in the autumn than in the spring spawning (see above, p. 664). Elmhirst (1945) stated that the larvae of P. maximus settle on Laminaria saccharina, while Hertling (1934) found a few young specimens attached to a drifting trunk off Heligoland. On only one occasion, however, did I find the spat of Pecten maximus, namely on 29 August 1952, when two specimens, 3'0 and 3'5 mm long respectively, were found on Desmarestia on the Bradda bed.…”

Section: Larvae and Spatmentioning

confidence: 99%

The breeding of the scallop, Pecten maximus (L.), in Manx waters

Mason

1958

Marine Laboratory, Aberdeen MATERIAL AND METHODS An important fishery for the scallop, Pecten maximus (L.), is carried on during the winter months round the Isle of Man. A knowledge of the breeding of this lamellibranch would be useful should legislation become necessary with regard to the fishery.Regular samples of scallops were dredged, whenever possible, at roughly weekly or fortnightly intervals throughout the period October 195o-0ctober 1952, from a depth of 13-16 fm. off Bradda Head and Bay Fine, near Port Erin. Approximately 8000 scallops of all ages up to 13 years were examined, though very few young ones were caught. Scallops were aged by means of the growth-rings on the shell, of which one is laid down each spring (Mason, 1957)· The gonad of every scallop was examined macroscopically and classified as regards degree of development (see p. 656). Pecten maximus is a hermaphrodite, the gonad consisting of separate male and female parts.Several gonads in each stage of development were examined histologically by means of transverse sections, and serial sections were prepared of the whole of some small gonads. The material was always taken so as to include both ovarian and spermatic tissue. Three fixatives were used, Bouin, Heidenhain's Susa, and Zenker, of which Bouin proved the most satisfactory.There is always some loss of reproductive cells from the cut surface of the gonad, and so all pieces to be fixed were cut large enough to allow for this loss. Penetration of the fixative was facilitated by making needle-holes in the material, which was then placed in the fixative and left for several days. The material was then cut into halves, each half containing both ovary and testis, and replaced in the fixative. This second cutting involved no loss of reproductive cells. After dehydration with ethyl and n-butyl alcohols, clearing in cedarwood oil and embedding in paraffin wax, sections were cut parallel to the newly-cut face. Sections were cut between 5 and 8 Jk thick, and stained with Ehrlich's acid haematoxylin and eosin.Fixation always resulted in a slight contraction of the gonad, and so did handling.