Predation is now considered the main cause of mortality in larval and juvenile fish (Hunter, 1984) and is therefore the most important factor controlling recruitment to the adult population. Marine fish larvae are prey for many different types of predator including medusae, crustaceans and larger fish. When predatory attacks are sensed both adult and larval fish may respond by making a 'C-start', a very fast, simultaneous contraction of the trunk musculature that deforms the body into a C-shape within 20 ms (Eaton & Hackett, 1984). This startle response is mediated by the Mauthner cells, a pair of prominent neurones in the hind brain or by other reticulo-spinal cells located in the same region. As a result of reciprocal inhibition and decussation of the cell axon, stimulation on one side of the body results in contraction of all the muscle on the contralateral side.

Fourteen specimens of the hepatopancreas of the Pacific white shrimp, Penaeus vannamei, were prepared for examination with the transmission and scanning electron microscopes and with the light microscope. The histology and ultrastructure of this organ is similar to that seen in other Decapoda. At the ultrastructural level, it was observed that B-cells rupture at approximately the level of gap junctions located on the lateral plasma membranes of the cells, and discharge the contents of their large vacuoles into the intercellular space. This efflux of enzymatic material may be the mechanism by which cells are released from the wall of the tubule at the proximal end: the rupture and collapse of a B-cell may be analagous to the removal of the keystone which supports an arch. Deprived of support, and lacking structural adaptations for cohesion (there are no desmosomes or interdigitations in the epithelium) and with the intercellular material digested, the remaining intact cells collapse into the lumen of the tubule. The lysis of individual cells of all types - R-, F-, and B-cells - may contribute to the tubules’ total complement of digestive enzymes.

Depredation by cetaceans and sharks on longline fisheries is a global issue that can have negative impacts on both animals and fisheries and has concerned researchers, managers and the fishing industry. Nevertheless, detailed information on depredation is only available for a few regions where the problem exists. With the purpose of evaluating killer whale depredation on longline-caught tuna (Thunnus spp.) and swordfish (Xiphias gladius) in the waters off southern and south-eastern Brazil and comparing it to shark depredation, data sheets were distributed to the captains of tuna vessels in Santos, south-eastern Brazil, between 1993 and 1995. Data on the catch per unit effort (CPUE) of tuna and swordfish and some records of interactions were also obtained from fishing vessel logbooks. Dockside interviews with fishermen and with researchers on board tuna vessels provided additional information. Killer whale and shark interactions were analysed per longline set and per trip. Killer whale interactions occurred from June to February, mainly between June and October, while shark interactions occurred year round. The number of sets and trips involving shark interactions was significantly higher than the number of sets and trips involving killer whale interactions. However, when depredation occurred, the proportion of fish damaged by killer whales was significantly higher than by sharks. Furthermore, killer whales removed or damaged significantly more hooked swordfish than hooked tuna, whereas sharks damaged significantly more hooked tuna than swordfish. This study also shows that cetacean by-catch is experienced by the tuna and swordfish longline fishery in Brazilian waters.

In 1933 an examination of Peringia ulvœ for larval trematodes was under-taken at Plymouth (Rothschild, 1936). No actual measurements were made at the time, but there appeared to be a relation between the species of trematode and the size of the individual infected snails. Thus the commonest species, Cercaria oocysta Lebour, 1907 (14% infection), and C. ubiquita Lebour, 1907 (4% infection), were found in 75% of the largest snails, while the rarer species, such as C. ephemera Lebour, 1907 (non Nitsch) (2% infection), and C. pirum Lebour, 1907 (0–1% infection), occurred most frequently in medium sized individuals.

Marine debris is a major challenge threatening ocean and coastal environment with no easy solution in coming years. The problem is totally manmade and extendeds to coastal areas around the world. The accumulation of marine debris is largely due to lack of awareness and environmental education among the public reinforced with mismanagement of municipal litter in coastal cities. Iran has about 2415 km of coastlines in the north and south of the country that suffer severely from a marine debris problem. Despite the great scale of the problem that leads to the shutdown of some beaches to beachgoers, there are no documented data on the abundance, composition and sources of marine debris dispersed on beaches. With the cooperation of marine biology student volunteers, we surveyed beaches at two scales, 100 m and 1 km searching for litter in varying ranges. The results revealed that the most common items are made of plastic/polystyrene. Tourism and recreational activities are responsible for more than 90% of litter production on the study beach. Fisheries and aquaculture are the second source of most abundant marine litter found on the beach with considerable distance from tourism activities. We conclude that lack of education about the consequences of marine litter is the main reason for marine debris at the study beach. Another reason is related to rapid construction of coastal areas and development of coastal cities with no proper infrastructure to manage municipal littering.

Many symbiotic organisms are narrowly distributed on one or a few host species. These associations are intriguing, as they invite the development of hypotheses regarding the pattern and process of speciation and serve as laboratories for the testing of methods of phylogenetic reconstruction (Kraus, 1978; Futuyma & Slatkin, 1983; Stone & Hawks worth, 1986). The evolution of host-specificity in the sea may be expected to be severely constrained by the difficulty of achieving reproductive isolation in taxa whose gametes are freely released into the water column and/or whose larvae are potentially widely distributed (Scheltema, 1977). Yet this difficulty may well be overestimated, given the recent demonstrations of limited gamete (Pennington, 1985; Yund, in press) and larval dispersal (Knight-Jones & Moyse, 1961; Ryland, 1981; Olsen, 1985; Jackson & Coates, 1986; Grosberg, 1987). Indeed, if gamete and larval dispersal are as limited as has recently been contended (Jackson, 1986), local isolation of populations may be a routine occurence, offering repeated opportunities for speciation.

Records of fish captures on power station intake screens were used to analyse the structure of the English and Welsh inshore fish community. The study was undertaken as part of a programme to predict fish captures at future power station sites. It was found that 118 of the 122 fish species known to live inshore were recorded from the screens of 12 coastal power stations. The maximum number of species at one site was about 80, achieved at fully marine localities along the English Channel coast. This number declined with increasing latitude and decreasing salinity.

Fish subdivide their use of the inshore habitat both spatially and temporally and the proportion of species complement within the major subdivisions of the habitat was remarkably similar at all sites. On average, 28 species were present simultaneously and these would include 4 pelagic, 8 demersal and 16 benthic species.

This study forms a contribution to a series (Angel, 1969; Clarke, 1969; Baker, 1970; Badcock, 1970) describing the biological results of a detailed investigation of the ecology of an oceanic area located in the eastern North Atlantic, close to the island of Fuerteventura (Canary Islands). The scientific background and objectives of the investigation, conducted during September to December 1965, have been described elsewhere (Currie, Boden & Kampa, 1969). Our main interest lay in the biological composition and acoustic characteristics of sonic scattering layers, and it was therefore considered essential to sample the principal elements of the pelagic fauna within the depth range 0–1000 m in as quantitative and detailed a manner as was technically possible. The resulting biological collections represent a unique body of material, the analysis of which is directly pertinent to the vertical distribution, diurnal migration and ecological interrelationships of the mesopelagic fauna.

Determinations of phosphate, silicate, nitrate, nitrite and ammonia have been made at frequent intervals at two Stations, L4 and El, in the English Channel off Plymouth between the autumn of 1930 and January, 1932. Determinations were also made quarterly at E2 in mid-Channel.

The year 1931 was an early one from the point of view of plankton production. The chemical data show that there was a small mid-winter outburst which gathered momentum during January and February. The main spring outburst started, however, early in March, carrying on fairly steadily until about the middle of May. The summer was characterised by exceptionally low phosphate and nitrate right through the water column due to very efficient utilisation in the spring and to the unusual hydrodynamical conditions. There was also a small autumn outburst.

The worms were housed in glass U-tubes, and were able to get a supply of aerated water from above by making pumping movements. The water movements were recorded kymographically. The experiments generally lasted for 24 hr. or longer.

Laboratory experiments showed that freshly liberated Spirorbis larvae settle on surfaces which bear previously settled individuals, in marked preference to bare controls, but that larvae which have been kept swimming for 3 hr., or longer, exercise less choice when setting.

When larvae are freshly liberated there is a great difference between the rate of setting gregariously, and the rate of setting in isolation; but after they have been kept swimming for 3 hr. this difference becomes less, owing to the larvae setting more rapidly both gregariously and in isolation. After swimming for about 8 hr. rates of setting fall off, and many larvae fail to settle, apparently through weakness.

I am greatly indebted to Dr D. J. Crisp for advice regarding this problem, and to him and Mr G. M. Spooner for much help with statistical treatment.

A few studies on the excretion of organic matter by marine phytoplankton in culture have been reported (Guillard & Wangersky, 1958; Wangersky & Guillard, 1960; Stewart, 1963; Hellebust, 1965). Eppley & Sloan (1965) reported extensive excretion in Skeletonema costatum (Greville) Cleve cultures as they approached senescence and emphasized that excretion is inversely proportional to the physiological activity of cells. Hellebust (1965) demonstrated the release of high amounts (up to 38% of the carbon assimilated) of organic matter by Sk. costatum cells exposed to low light intensities. It is apparent that more knowledge is needed in order to define the intra- and extracellular factors affecting the excretion.

Infestation of cage cultured Atlantic salmon by the external parasitic copepods Caligus elongatus (Nordmann) and Lepeophtheirus salmonis (Kröyer) is a serious cause of loss of production in the commercial sea water culture of this species. The copepods feed on the mucus, skin and blood of their hosts (Kabata, 1974; Brandal et al., 1976) causing irritation and lesions. Loss in production due to infestation by lice occurs directly by the mortality of fish from osmotic shock and indirectly from a probable reduction in growth, from secondary infections such as vibriosis (Wootten et al., 1982) or by increasing vulnerability to ultraviolet radiation damage (McArdle & Bullock, 1987).

Part I. After a brief statement of the present unsatisfactory position regarding the life history of Polystomella crispa, an account is given of experiments with various fixatives on P. crispa, collected near Drake's Island, Plymouth. A method is described for the cultivation of Polystomella in diatom cultures, especially with Navicula mutica var., with which a flagellate (Bodo sp.) was constantly present. The identification of individual Foraminifera, and determination of growth, were often possible by some irregularity in the shell, or by noting the attachment of one or more stalked egg cocoons of an unknown turbellarian worm. The feeding of Polystomella on diatoms seized by the pseudopodia outside the shell is described; the structures previously taken for ingested algal cells inside the shell are shown to be foraminal plugs (‘bouchons’ of le Calvez) which are discarded from time to time and thrown out of the shell along with the excretory granules (xanthosomes), mostly via the canal system.

Part II. Notes are given on the microspheric form and its reproduction, through the spring and summer, by schizogony. The rearing of two broods in laboratory cultures is described, with an account of the formation of a new chamber to the shell. It is concluded that a complete life cycle consisting of one microspheric and one megalospheric phase occupies a period of about two years.

Part III. Sporulation of the megalospheric form is described as seen during life; and various factors are discussed which might affect the process. The relatively small size of the reproducing Polystomella with which Lister worked is ascribed to their having lived under less favourable conditions. From a study of stained preparations, certain details are added concerning the opening up of the shell, presumably to facilitate the eventual escape of the flagellate swarm spores; also concerning the accompanying cytoplasmic and nuclear changes. Some account is given of the form and structure of the swarm spores, both alive and in permanent preparations. Experiments are described which constitute an attempt to carry the life cycle beyond the stage of sporulation. They are so far unsuccessful, with one possible exception, under all the various experimental conditions which are briefly discussed in their turn.

Species of Chrysochromulina (Prymnesiophyceae) were screened for their ability to ingest inert material and live cells of a small green flagellate. The species C. brevifilum showed a marked preference for the small green flagellate over carmine particles and the rate of ingestion of the flagellate was proportional to its concentration and inversely proportional to light intensity. Ingestion was also higher by phosphate-starved Chrysochromulina, and a clear predator/prey relationship was demonstrated with C. brevifilum clearly benefiting, in terms of growth rate, from the ingestion of the small green flagellate. Electron micrographs confirmed that digestion occurs.

The reproductive biology of two aplacental viviparous deep sea sharks, Centroscymnus coelolepis and Centrophorus squamosus has been studied from 1735 and 675 specimens respectively, collected with bottom trawls between 600 and 1400 m depth off the west coast of the British Isles. A macroscopic maturity scale indicates that for both species, size at first maturity is greater in females than in males. In Centroscymnus coelolepis, genital maturity occurs at an average length of ∼86 cm for males and ∼102 cm for females. In Centrophorus squamosus, males are mature near 98 cm and females near 124 cm total length (TL). Smallest juveniles of both species are absent from catches: no specimens of Centroscymnus coelolepis shorter than 58 cm, nor specimens of Centrophorus squamosus shorter than 84 cm have been recorded. Ovarian fecundity is higher in Centroscymnus coelolepis than in Centrophorus squamosus. A maternal supply has been demonstrated for Centroscymnus coelolepis. Litter size has been estimated only in C. coelolepis because no pregnant females of Centrophorus squamosus were recovered. A dwarf embryo and a pair of twins have been observed. Segregation by sexual stage of development shows that immatures are generally found at greater depths than adults.

The distribution of the warm-water barnacle, Balanus perforatus, was surveyed along the south coast of England and the north-east coast of France between 1993 and 2001, repeating work carried out between the 1940s and 1960s. The species has recovered from catastrophic mortality during the severe winter of 1962–1963 and was found over 120 km (UK) and 190 km (France) east of previous records on both sides of the Channel. The presence of the species in the eastern Channel refutes suggestions in the 1950s that larvae, and hence adults, would not be found east of the Isle of Wight because of reproductive sterility close to the limits of distribution. Brooding of specimens translocated to Bembridge, Isle of Wight, commenced in May, earlier than previously observed in British waters, and continued until September. The stage of embryo development at Bembridge in mid-August was comparable to that of the large population at Lyme Regis, Dorset 100 km further west. However the size of brood per standard body weight was greater at Lyme Regis. Factors influencing the rate of colonization and further geographic range extension of the species as a possible result of climate change, are discussed.

The community structure of decapod crustacean assemblages was established and analysed from two experimental trawl samplings. The data were taken in the south-west Balearic Islands (Algerian Basin, western Mediterranean Sea) at depths ranging from ∼200 to 1800 m. The results of multivariate analysis indicate that the community structure remained constant between samplings. The analysis also revealed that there exist differences between bathyal decapod communities at a regional level (<1000 km) when compared with well-studied nearby areas. The differences relate mainly to the relative contribution of different species and feeding guilds, not to the taxonomic composition of the assemblages studied. It is proposed that these differences result from contrasting surface production regimes (coastal vs open sea) and food web organization (relative dependence on mesopelagic or infaunal prey).

Between May 1961 and November 1970 almost monthly visits were made to Duckpool, an exposed shore on the north coast of Cornwall, where Sabellaria alveolata (L.) is the dominant organism on low-level rocks uncovered only by spring tides. Massive colonies several feet across and up to some 2 ft thick, formed mainly of shell particles cemented together by the worms, as well as many smaller colonies and single tubes, here reach their maximum development in south-west England.

Selected sites and colonies were photographed and some measured at frequent intervals over long periods of time. comparative studies of long series of colour transparencies examined closely with a binocular microscope have proved invaluable in elucidating the manner and rate of growth of varied types of colonies, their lengths of life and the manner of their ultimate destruction. Detailed histories of these selected colonies are given in this paper and reveal much that was previously unknown or only guessed.

A short spawning period every year in July initiates each new generation. Experimental work, already published, had shown that individuals develop at different rates, the final stage with ability to settle being reached at any time from 6 weeks to 6 or more months, and when reached the ability can be retained for some weeks. This accords with observations on the shore, where settlement takes place in any month between late August and the following early May, or rarely June. The intensity of settlement varies enormously from year to year, there being none in some years, with slight or moderate or heavy settlements in others.

A new midwater trawl based on that designed by Tucker (1951) is described with details of opening and closing equipment, acoustic release gear and depth telemetering pinger. An account is given of the method used in operating the xtrawl from R.R.S. ‘Discovery’.