The use of freeze-branding as a field-marking technique for flatfish is described. Similar recapture rates were obtained for flounders marked on the coloured, or eyed, side and for those marked on the white, or blind, side during the first two years after marking. Brands on adult flounders were still identifiable more than four years after release of the fish. The branding technique is also applicable to plaice.

The oxygen consumption of the intertidal teleost Blennius pholis L. has been investigated during and subsequent to quinaldine anaesthesia, using a continuous flow apparatus. Marked reductions in oxygen consumption were noted in high concentrations of quinaldine (10 and 20 ppm), and both entry into anaesthesia and recovery from it were rapid. A period of enhanced oxygen consumption followed anaesthesia, except in the lowest concentration of quinaldine (1 ppm). Experiments conducted over a 4 h period with three different salinities (100%, 30% and 10 % sea water) indicated that, under the influence of 10 and 20 ppm quinaldine solutions, the fish more resembled an osmoconformer than an osmoregulator. During anaesthesia, water was lost osmotically in 100% sea water, and gained in the more dilute salinities, although it was possible that some osmotic regulation continued. Physiological measurements indicated that quinaldine is suitable for the capture and marking of fish; for surgical procedures it should be mixed with another anaesthetic, for example MS-222, due to the retention of a response to vibratory stimuli.

Abra alba and Abra tenuis are closely related marine bivalves. They both inhabit similar types of sandy-mud sediments but they prefer different localities. The smaller A. tenuis is found in a few scattered intertidal mudflats, whereas A. alba is more widely distributed and in great abundance in the coastal waters of north-west Europe. The latter can be found at any depth between low-water mark and 80 m (Tebble, 1966; Ansell, 1974) and often forms the dominant species of shallow water benthic communities.

The reproductive cycle of the two species has been studied and compared as a part of a wider ecological investigation. There is minimal literature concerning the reproduction of A. tenuis but A. alba has received a lot of attention, because it forms a major source of food for flatfish. However, most of the earlier investigations are confined to the time that spawning occurs with the evidence derived from either the time of the year that larvae appear in the plankton (Lebour, 1938; Jorgensen, 1946; Fosshagen, 1965; Muus, 1973; Rasmusen, 1973), or the time of the year that juveniles first appear in the bottom samples (Orton, 1924; Ford, 1925; Stephen, 1932). The inadequacy of such indirect methods has been discussed by Seed (1969,1975, 1976). Ansell (1974) derived the reproductive cycle of A. alba from seasonal changes in the biochemical composition. In the present investigation, histological techniques have been used, since they are considered to offer the most reliable information about the reproductive cycle (Seed, 1969, 1975, 1976).

Echinoderms are not generally considered to experience significant dilution of the surrounding medium in their usual marine habitats and so it is to be expected that, due to the absence of any obvious excretory organ, the ionic composition of the body fluid would be similar to that of the ambient sea water. In general this has been confirmed by previous workers for many species of echinoderm. Binyon (1966) lists the results of workers who have determined osmotic pressure and/or ionic concentrations in the perivisceral and/or ambulacral fluids of many echinoderms. With reference to the perivisceral fluid in asteroids there is usually a small excess of potassium (9–16%) which is maintained in the more euryhaline species and in those acclimatized to reduced salinity. Generally, the chloride content is similar to, or a little higher than, that in the surrounding sea water. In echinoids there is little difference in the potassium content and chloride concentrations with respect to sea water though there may be a small increase in the former ion. In the holothurians, there is little regulation of potassium ions. Such concentrations which have been determined for the chloride ion in this group are found to be a little higher than in sea water. The sodium concentration in the perivisceral fluids of echinoderms tends to be similar to, or slightly lower than, that in the surrounding sea water. However in the ambulacral fluids of the water vascular system it has been shown that the potassium concentration is 20–90% higher in some species of asteroids and echinoids (Robertson, 1949; Binyon, 1962,1966). The fluids of the water vascular system of echinoderms, analysed to date, have concentrations of sodium ions lower than in the ambient sea water. From the available evidence, there appears to be little difference between environmental and ambulacral chloride concentrations.

Previous studies on the significance of dissolved organic compounds in the nutrition of the smaller species of the phylum Pogonophora (Little & Gupta, 1968, 1969; Southward & Southward, 1968, 1970) were handicapped by lack of information about the levels of free amino acids in the tissues. In this brief note we give preliminary results for four species, using a modification of the technique described by Clark (1964, 1968, 1973) to estimate the amino acids in extracts of the whole body.

Montagu's blenny, Coryphoblennius galerita was reared to late larval stage under laboratory conditions. The adult male guarded the eggs and aerated them with its tail during the incubation period. The larvae had a small amount of yolk on hatching and although they appeared to be feeding on the variety of food introduced, no food was observed in the gut. The gas bladder, observable above the gut in all larvae, was filled with gas only in the one specimen, killed at 45 mm T.l., which survived after the yolk was utilized, and in some 4 mm specimens taken from the plankton off Mweenish.

Descriptions are given of the larval stages and of juveniles taken from rock pools.

Production rates and production/biomass ratios have been estimated for a large number of macrobenthic species (Hargrave, 1977; Robertson, 1979). The usefulness of such estimates is limited by a lack of information on their temporal and spatial stability; we are aware of only one study (Sarvala, 1980) in which production has been estimated for more than one year. The present study investigates the stability of the production (P), biomass (B) and P/B values of two polychaete species, Nephtys hombergi Savigny and Ampharete acutifrons (Grube), over a 5-year period.

The stomach contents of Lepidion eques trawled at depths ranging from 500 to 1250 m on the Hebridean Terrace (56°-57° N, 9°-11° W) are analysed relative to size of fish, depth of habitat and season of the year. Of the 1281 fish examined, 47% had everted stomachs, 29% empty stomachs, 2% had food that was totally unrecognizable while 21% had food whose constituents could be identified. The principal dietary components are the epibenthic and hyperbenthic decapod crustaceans, although a wide variety of other organisms also occur as minor components. Benthic infauna and sessile epifauna are absent from the diet. L. eques therefore feed predominantly on organisms swimming immediately above the sea-bed or actively moving over it.

An occurrence of ‘milky water’ which covered a wide area of the North Sea in June 1975 is described. The water contained 20 mg/1 of an oil which was shown by capillary GC-MS to consist mainly (> 80%) of two wax esters 34:1 and 36:1. Analysis of the acids and alcohols released by hydrolysis, and interpretation of the wax ester mass spectra, indicated that the 34:1 ester was almost entirely composed of the alcohol-acid combination 20:1–14:0 and the 36:1 ester was composed of 22:1–14:0 (75%) and 20:1–16:0 (19%). Wax esters of virtually the same composition predominate in the lipids of the copepod Calanus finmarchicus which has the implication that the ‘milky water’ was caused by ageing of the oil released following a mass mortality of copepods. The lack of polyunsaturated wax esters and of astaxanthin is ascribed to oxidative degradation of these labile lipids following release into the sea. A copepod origin for the milky water is further supported by its containing small amounts of cholesterol and pristane, both of which are common to Calanus species.

Bioassays designed to test the effect of single or some combination of environmental factors or pollutants on aquatic organisms are usually performed in constant levels of the imposed conditions and commonly in static rather than flowing water. The reason for this is usually one of convenience and practical simplicity and the results are valid for the set of conditions imposed. However, since aquatic organisms are rarely exposed to constant and static conditions, the results of such tests cannot with confidence be extrapolated to field conditions. This is particularly true in the case of estuarine organisms for which, change is the rule.

One commonly held opinion about the metabolism of intertidal gastropods has recently been expressed by Newell (1970) who stated that in moist air these - as well as other intertidal - animals will respire air ‘whereas under conditions of desiccation closure of… the operculum… may result in anaerobic respiration occurring with the production of lactic acid’ (pp. 266–267). However, although anaerobiosis certainly does occur in intertidal gastropods (Patané, 1957; McMahon & Russell-Hunter, 1978) the conditions controlling this type of metabolism are far from clear. Moreover, recent studies (summarized by de Zwaan, 1977) have revealed a complex pattern of anaerobic metabolism in invertebrates in which the production of lactate is only one - and certainly not the most important - element.

Young estuarine bass of the 1976 and 1977 year classes were examined for gill parasites between February 1978 and June 1979. 344 specimens of the copepod Lernanthropus kroyeri were recovered from 177 of 289 fish. The distribution of the copepods on the gills showed clear preferences for site of attachment. With 48 such sites delineated per fish, 143 of 183 female copepods favoured a single site – the internal face of the medial sector of the posterior hemibranch of the second gill arch. 57 of 161 male copepods chose attachment to the external face of the medial sector of the anterior hemibranch of the second gill arch. Only seven copepods in all were found attached at any of the twelve possible sites on the first gill arch, and none at all at the six possible sites on the posterior hemibranch of the fourth gill arch. Explanations for the observed distribution are discussed in terms of the strength of the branchial ventilation currents over the different gills coupled with observations on the special respiratory adaptations of these parasites.

Re-examination of the original and subsequent data from Secchi disc studies leads to a revised constant in the light attenuation formula applicable to general field-work.

In theory, the depth at which a Secchi disc disappears from an observer's sight, Ds, is inversely proportional to the sum of attenuation coefficients for diffuse and collimated photopic light (Tyler, 1968). By definition, photopic light is measured by a sensor with the same spectral response curve as the normal human eye. In practice, the usefulness of the theoretical equation is restricted. More commonly, a simple empirically derived formula is used to estimate the attenuation coefficient for diffuse downwelling light, k, directly from Ds. Poole & Atkins (1929), in their pioneering work on light penetration in the sea, derived the relationship k × Ds – 17 for water in the English Channel. This formula is used extensively by workers who are unable to measure k directly and it is given regularly in oceanography and marine biology texts. More recently, a number of investigators have proposed alternative equations relating k to Ds in different regional seas (Table 1). However, Idso & Gilbert (1974) have fitted data of some of these authors, together with measurements of their own, to the original Poole and Atkins formula with good correlation. They suggest that k × Ds = 1.7 is a universal approximation for all natural waters. In view of the continuing importance of the Secchi disc as a measure of underwater light for primary production calculations and other studies, a universal formula is certainly desirable. However, re-examination of the Poole & Atkins measurements has revealed an error in the method of calculation of k.

Whilst there have been a number of fundamental studies illustrating the effects of Earth's rotation on the flow around submerged obstacles (Hogg, 1973) and islands (Longuet-Higgins, 1969) there appear to be relatively few studies that include both non-linear advective and frictional effects (Huthnance, 1972), and few were found describing the stagnation region that develops in the lee of the flow due to the advection of vorticity generated by the frictional stress associated with a beach gradient (Pingree & Maddock, 1979). In this paper some rotational flow patterns that can develop around an island due to these effects are examined using a numerical model and an overall attempt has been made to illustrate the possible use of numerical models as a tool for theoretical investigations in areas of study that until recently have been exclusively analytical or experimental. An island is surrounded by a uniform beach gradient and the model illustrates how varying bottom topography modifies a steady flow due to both frictional and Earth's rotation effects. Only non-oscillating flows with steady wakes are considered here so that the vorticity sources and sinks can be examined as simply as possible. Stagnation regions due to frictional effects are known to be important in determining sediment deposition and the effects of the Earth's rotation may result in increasing asymmetry in sediment distributions (Johnson, Vogt & Schneider, 1971).

From analyses of the gut content of Sabella penicillus L. Hunt (1925, as S. pavonina) showed that the food consists mainly of finely sorted plankton and detritus. The chief constituents were usually bottom-living diatoms, but planktonic forms when present made up the bulk of the food. Peridinians, silicoflagellates, foraminifera and tintinnids were also found to occur. These observations were confirmed by Nicol (1930) and in the present study, in which some individual worms were found to contain very large numbers of planktonic dinoflagellates, and pieces of red, green and brown algae, and encysted flagellates.

In England the fisheries for both scallops (Pecten maximus) and queens (Chlamys opercularis) expanded rapidly in the 1970s. Considerable research has been undertaken to develop an effective method of surveying stocks of these species in order to assess the impact of this greatly increased fishing effort on commercial populations. Visual photographic surveys seemed likely to provide the best means of assessing populations (Pickett & Franklin, 1975) and this paper outlines the preliminary results obtained from such a system - a towed sledge carrying both television and still cameras, developed at the Plymouth Laboratory.

The cirratulid polychaete Cirriformia tentaculata (Montagu) may be found in gravelly mud or sand often beneath large stones in pools between tide marks. It is usually associated with reducing conditions indicated by blackened mud or sand and the distinctive odour of hydrogen sulphide. It occurs also in crevices that retain stagnant water at low tide. The worm does not make a permanent burrow but lies in different postures to enable the branchiae and feeding tentacles to be extended on to the surface, where they are bathed by the overlying water. The mucus-lined burrow is not irrigated.

Cirriformia tentaculata encounters two respiratory problems. When covered by water the branchial filaments can take up oxygen which is then circulated by means of the well-developed vascular system with blood containing haemoglobin in solution. While the branchiae may lie in a well-oxygenated medium the main body of the worm lies in a highly reducing substrate. The sediment immediately surrounding the worm is commonly black and there is no oxygenated layer as occurs in burrows which are irrigated and provide an envelope separating the animal from a potential oxygen-sink. If exposed by the tide the branchiae are withdrawn or clump together and cannot function effectively. Even when covered by the tide the branchiae can be rapidly with-drawn, presumably to avoid loss by predation, and under all these conditions the animal must experience hypoxic or anoxic conditions of varying duration of up to several hours.

We have examined the ability of Cirriformia tentaculata to maintain oxygen uptake under decreasing oxygen tension, the oxygenational properties of the haemoglobin, the oxygen capacity and blood volume.

Talitrus saltator, a supralittoral, sand-beach amphipod, exhibits a nocturnal, circadian, locomotor rhythm entrained by the natural photoperiod (nLD). A phase-response curve (PRC) (light pulse: 2h/400 lx) of the free-running rhythm exhibits a conventional shape; steady-state delay shifts of approximately 3·5 h occur in response to light pulses around subjective dusk, with similar advance shifts when exposed to light pulses around dawn. The seasonal variation of the overt expression of the rhythm indicates that entrainment is predominantly non-parametric, while the constant phase-angle difference between the peak of locomotor activity and dawn confirms the latter as the effective field signal for entrainment. The qualitative relationship between the time scale of the PRC and nLD, together with the absence of any seasonal variation in the periodicity of the free-running rhythm (τ), suggests that entrainment occurs through the interaction of phase shifts defined by the PRC, essentially in response to the systematically changing photoperiod.

Dinoflagellate blooms, chiefly of Gyrodiniwn aureolum Hulburt, occurred along the south and south-west coasts of Ireland in August and September 1978 and mortalities of shore animals and of rainbow trout Salmo gairdneri held in sea cages were described from Dunmanus Bay (Parker, 1980). Since May 1978 four rocky shore sites in Bantry Bay and one in Dunmanus Bay have been monitored monthly (Myers, Cross & Southgate, 1978, 1979). At each site a permanently marked transect is monitored, limpet shell lengths are measured in marked quadrats at M.H.W.N., M.T.L. and M.L.W.N. and settlement, growth and mortality of barnacle species are studied on vertical rock faces. Discoloration of the water was observed at all five monitoring sites in August 1978 but no effects on the littoral or sub-littoral fauna and flora were detected (Cross & Southgate, 1980).

In 1979 a reddish-brown discoloration of the water in Bantry and Dunmanus Bays was first observed in early September. Surface water samples taken at the regular sampling sites between 5 and 10 September revealed very high densities of Gyrodinium aureolum. Slight discoloration of the water persisted at Eagle Point until October and at Glengariff Castle until early November. During this period mortalities of shore fauna were observed at four of the regular sampling sites. Highest mortalities were observed at Pointabulloge in Dunmanus Bay. When visited on 8 September many Patella spp. on the transect were either dead or, if alive, could easily be removed. An estimated 75% of Gibbula umbilicalis were lying inverted in rock crevices with partially opened opercula which they could close only slowly.

Actinia equina var. mesembryanthemum, the beadlet anemone (Stephenson, 1935), is a very common and widely distributed littoral anthozoan, whose sexual reproduction shows several interesting characteristics. Adult sea anemones of both sexes brood planulae and more advanced developmental stages within the gastrovascular cavity, although earlier embryonic stages are rarely found brooded in this way. Chia & Rostron (1970) suggest that embryos are expelled from the parent female anemone at an early stage and pass through a free-living phase before re-entering anemones of either sex for brooding. However, recent work (Cain, 1974) suggests that juvenile anemones are genetically related to the adult anemones in which they are brooded, and also the distribution of genetic material during sexual reproduction appears to be abnormal (Carter & Thorp, 1979). In an attempt to achieve a better understanding of the unusual sexual reproduction of this species, an ultrastructural investigation of gametogenesis was undertaken. This paper describes the fine structure of the spermatozoon within the testis.