Laboratory-reared herring larvae adjusted several characteristics of their swimming behaviour to the presence of food in the experimental tank. When food density was low, as in the outer limits of a food patch in the sea, the larvae increased their turning frequency, an exploratory behaviour to locate the centre of the patch. At a higher prey concentration, such as in the centre of a food patch, the larvae crossed their previous swimming path more frequently, indicating a local search strategy aimed at foraging in the centre of the patch.

The prey of actively foraging planktonic predators, such as fish larvae, is patchily distributed. The main factors governing the ability of the predators to encounter prey are the relative velocities of predator and prey, and the prey detection radius by the predator relative to the distance between prey items (Gerritsen & Strickler, 1977). The enhancement of encounter rate by turbulence through its effect on relative velocity has been widely discussed in the literature since Rothschild & Osborn's (1988) publication. However, an effective forager should be able to adjust its behaviour to optimize prey encounter by, for example, altering its position in the water column in relation to conditions of turbulence, or modifying its searching behaviour in response to spatial aggregation of prey. This latter aspect has received comparatively little attention. Different swimming modes have been described in herring (Clupea harengus L.) larvae and in larvae of many other fish species. Foraging larvae swim in a more linear path between food patches and follow a more complex track when a patch of prey is located.

To date, the oedicerotid amphipod Monoculodes gibbosus Chevreux, 1888 is known in British seas from only two individuals collected from Loch Fyne and lodged in the Robertson Collection at Millport (Moore, 1984). Recent intensive research on other species in this family in the Clyde Sea area by one of us (D.J.B.) has resulted in the sporadic capture of further individuals of M. gibbosus (128 individuals in total) from Inchmarnock Water, southern Loch Fyne. This material allows us to expand our knowledge of the species' morphology, live colour, population structure, fecundity, egg size, breeding season, diet and behaviour. Notes on these topics are presented below.

A practical method for separating eggs of hake, Merluccius merluccius (Pisces: Merlucciidae), from samples of mixed plankton is described.

Ligia italica Fabricius is a day-active isopod on the shores of Madeira. The population migrates up and down the shore with the tide, browsing on lichens and macroalgae. Shore bird predation is negligible; foraging wall lizards are the only daytime predators. Ligia italica retreats into crevices at night. It exploits plant material within supralittoral and intertidal pools and enters pools with salinities as high as 74‰. Ligia italica emerges from pools at intervals to breathe in air; such emersion lasts no more than two minutes. Ligia italica on Madeira has no colour change ability, the isopods remaining dark grey/black whatever the background.

A combination of photography and subsequent image analysis of the photographs has been used to measure maximum length, perimeter length and total area of fronds of tagged Fucus serratus L. as part of a study of the growth of this species on the Yorkshire coast. Maximum mean growth rate of 0·26 cm d-1 was observed during June–July. Minimum mean growth rate of 0·01 cm d-1 was observed during October-March. The method is relatively quick and convenient, and has the advantage that in addition to apical growth of the longest and/or other branches, lateral growth and total growth in surface area can all be recorded, while loss of tissue can also be determined. A further advantage is that a photographic record is obtained of the history of each individual plant.

The suitability of using intra-peritoneally attached miniature 300 kHz acoustic transmitters to study the behaviour of juvenile bass (Dicentrarchus labrax) between 235 and 370 mm in length was assessed. A laboratory study indicated minimal effects on the subsequent survival and behaviour of juvenile bass. A field study carried out indicated the potential use of the transmitter for telemetry studies on juvenile bass.

The use of stolons in competitive interactions between several species of bryozoans growing in Townsville Harbour, North Queensland is described. Stolonal growth resulted in overgrowth reversals and redirected growth in interactions between Schizoporella unicornis and Watersipora subtorquata. These results suggest that stolons may play an important role in bryozoan interactions

Two morphotypes of the venerid bivalve Chamelea gallina (L.), viz. C. gallina s.s. and C. striatula, were electrophoretically compared at seven polymorphic enzyme loci. In three populations from the Ría Formosa (southern Portugal), both morphotypes occurred sympatrically. Analyses of genotype frequencies in these mixed populations revealed departures from Hardy-Weinberg expectations at nearly all loci. These deviations were mainly attributable to a Wahlund effect, caused by mixing the two morphotypes. Nei's mean unbiased genetic distance between the two forms was D=1·138, while the mean genetic distances between populations within morphotypes were D=0·083 in C. gallina s.s. and D=0·229 in C. striatula. It is therefore concluded that C. gallina and C. striatula are reproductively isolated (biological) species, the geographical distribution of which is outlined.

The pulsed-Doppler flowmeter permits continuous, non-invasive measurement of blood flow through several arteries simultaneously. Summation of volume flow rates through all arteries leaving the heart allows determination of cardiac output, stroke volume, and the percentage of cardiac output delivered to each region of the body. The use of this system for investigating changes in arterial perfusion as well as its calibration in situ are described.

The microhabitat and morphology of Grubea cochlear (Monogenea), a rare gill parasite of Atlantic mackerel (Scomber scombrus), were investigated for a sample of fourteen parasite individuals obtained from Lyme Bay, southern England. Grubea cochlear showed a preference for the inner hemibranch of the fourth gill arch, this localization contrasting with that of the related and sympatric species Kuhnia scombri. The morphology of G. cochlear in this sample differed slightly from some of the previously documented specimens, especially with regard to the number of small genital hooks and the relative size of the haptor. It is suggested that geographical morphological variation may occur in this species.

The echiuran worm Thalassema thalassemum (Echiura: Echiuridae), is a deposit-feeder which uses its proboscis to collect sediment particles for ingestion. The proboscis is highly extensible and is used with dorsal surface downwards to skim particles from the sediment surface. Alternatively, the distal portion of the proboscis is arched over and the ventral surface of the tip is held against the sediment surface where ciliary movement facilitates particle collection. These methods are used in combination and collected material is moved back along the proboscis, the edges of which are rolled to form a closed tube. Burrows appear to be U-shaped with one predominantly inhalant and one exhalant opening. Faecal pellets are periodically ejected forming small mounds around exhalant openings and mean rates of 1·83 and 2·80 g dry wt d−1 were measured suggesting that, in sufficient densities, this species could make a significant contribution to macrofaunal bioturbation.

Columbus crabs, Planes minutus (L.) (Crustacea: Brachyura) are often found on the postero-ventral surfaces of sea turtles, particularly the loggerhead Caretta caretta (L.) (Testudines: Cheloniidae). There has been a general acceptance of a hypothesis that the crabs feed upon turtle faeces. However, evidence is presented here to demonstrate that Planes has a ‘cleaning’ role, feeding on other epibionts (e.g. barnacle cyprids, parasitic amphipods) during daylight hours. At night it is likely that the crabs feed on neustonic animals (e.g. euphausids). The species is also cannibalistic.

Intracellular granules have been isolated from the digestive gland of the shore crab Carcinus maenas (L.). These granules are normally shed from this tissue during the digestive cycle and are shown to occur in considerable numbers in the faecal strands. The granules are amorphous to x-ray diffraction and remain in this state in sea-water for several weeks, although they will transform into crystalline apatite in simpler saline solutions. The fate of these deposits in the marine environment is discussed in relation to their contribution to sediments and phosphorites.

The cellular composition of the mantle tissue of Mytilus edulis L. was determined, using quantitative microscopy (stereology) techniques, in three populations of mussels from differing environments, and the data compared. The results indicated that mussels from an estuarine or sheltered coastal environment had a greater proportion of adipogranular tissue than animals from an exposed, open coastal environment. The difference in cellular composition was attributed to differences in nutrient availability in the water column between the various sites. A 15-month transplantation of mussels from an open coast to estuarine conditions resulted in a decrease in the proportion of vesicular connective tissue in the mantle and an increase in gamete production. This suggests that Mytilus edulis can exhibit a high degree of phenotypic plasticity by using not only the more conservative strategy of nutrient storage during periods of high food availability, but also the more opportunistic approach of maximizing gamete production when conditions are favourable.

Despite extensive studies on settlement of the cypris larva of Balanus amphitrite amphitrite Darwin (Crustacea: Cirripedia), the fine structure of the putative settlement receptors of this species has not been described. This study presents observations made with the scanning electron microscope of the fourth antennular segment and its associated setae.

Long-term surface wave records from various parts of the English Channel are used to determine the percentage of time during a year for which waves disturb the sea-bed. Most of the bottom sediments are rarely disturbed by waves (<1% of the time), due to water depth and sediment grain size. The coastal zones (<30 m), including the embayments, experience significant wave disturbance at the sea-bed (i.e. >5–10%). The general distribution of surficial sediments can be explained in terms of tidally-induced processes alone. Even in areas where wave activity is high, fine-grained sediment transport is controlled by the same mechanisms.

The development of the female gonad in Loripes lucinalis (Lamarck) from Brest Harbour (Brittany, France) was examined over a one-year period. Throughout the year, several size classes of eggs were observed, and spawning was seen to occur twice. A major spawning occurred in May leaving the gonad completely empty in June. A minor spawning is also thought to have occurred between the November and December sampling periods. These spawnings do not seem to correlate with the classical environmental factors often associated with gametogenesis and spawning, namely temperature and chlorophyll a levels. The energy for gametogenesis seems to be obtained from the transfer of metabolites to the oocytes via specialized follicle cells. These metabolites are believed to be of heterosynthetic origin. An inverse relationship exists between the thickness of the follicle cell epithelium and the occupancy level of the gametes. During periods of gonadal proliferation, these cells represent the nutritive cells of the gonad, but during periods of non-proliferation they make up a somatic tissue used for metabolite storage until conditions are adequate for gonadal development.

Juvenile mussels (Mytilus edulis, Mollusca: Bivalvia) were subjected to a simple assay to investigate the pattern and timing of the shift from high copper resistance of the veliger larva to the lower resistance of the adult. The level of resistance found in veligers persists in mussels of 1 mm shell length (400 ppb Cu; LT50, 12.5 d) while the lower adult level of resistance is reached at a shell length of 5 mm (400 ppb Cu; LT50 2.8–5.3 d). Resistance declines gradually, being significantly correlated with shell length (P<0.02) such that size differences explain 88% of the variation in copper resistance among juvenile mussels.

Examination of extracts of tissues of a leatherback turtle, Dermochelys coriacea (L.) (Reptilia: Dermochelyidae) by high-performance liquid chromatography inductively coupled plasma-mass spectrometry has demonstrated the presence of arsenobetaine, arsenocholine and inorganic arsenate in heart muscle and liver, and arsenobetaine and inorganic arsenate in pectoral muscle. Although arsenobetaine was the major form in all tissues, inorganic arsenate and arsenocholine accounted for 50% and 15% respectively of arsenic in aqueous extracts of the liver.