From May, 1922, onwards the sq. metre bottom-sampler has been used to collect samples of the bottom-deposits with their animals, in the waters off Plymouth. The animals have been removed as soon as possible after capture by passing the samples through a series of sieves, and have been preserved in alcohol, to be identified and counted ashore. The present report deals with the distribution of the species represented, in the light of Petersen's Community investigations in Danish waters.

I express my thanks to Dr. Allen, Dr. Orton, Mr. Hunt, and Mr. Smith, of the Plymouth Laboratory, for their kind help in the identification of the material. I am particularly indebted to my friend, Mr. R. Winckworth, a late member of the staff, who has not only gone over with me the bulk of my collection of lamellibranchs, but has provided me with an excellent type series as complete as the material would allow.

The extensive use of his bottom-sampler in Danish waters and elsewhere has enabled Dr. C. G. Joh. Petersen to advance an opinion that “as a rule it is best to regard the animals living on the sea-bottom as communities, just as botanists group together the vegetation of the land into plant communities, even though in the present state of our knowledge it is impossible to show how intimate the mutual relations are between the animals of the sea in the single cases.”

It will probably assist the reader if I commence with a short summary recalling the more important points, concerning the recognition of communities, which have been advanced by Peterson, and in doing so I shall adhere closely to his own words.

INTRODUCTION

It is apparent, in a review on the decapod hepatopancreas (Gibson & Barker, 1979) that there is some consensus of opinion that the epithelium consists of E-, R-, F- and B-cells and M-cells (Al-Mohanna, Nott & Lane, 1985). Also, it is agreed that the gland produces enzymes and absorbs, digests and stores nutrients and excretes waste material. However, the apportionment of these functions to the different cells and the descriptions of the cytological processes involved are variously explained. Thus, the activity of proteases and amylases has been demonstrated in the secretion produced by the gland but the source of these enzymes is attributed to different cells and various modes of secretion are proposed. Also, no secretion granules of the zymogen type have been seen.

There are probably two main reasons for the inconsistent interpretation of the activities of the cells. First, the different stages of the feeding and moult cycles are not taken into account and both these affect the cytology of the gland. Second, some of the functions have been deduced from observations of the fine structure without any experimental treatments to demonstrate more directly the processes involved. In the present work all the animals are taken at the same moult stage and observations are made throughout the feeding cycle. Also, aspects of the function are studied with markers which are administered in the diet and injected into the blood. The activities of hydrolytic enzymes associated with the different epithelial cells have been studied but these will be the subject of a separate publication dealing with the cytochemistry of the digestive processes.

1. Echinus esculentus was studied from four localities in the Isle of Man and from one in the Clyde.

2. The inshore races are thicker shelled and natter, and on all grounds the urchins become taller with increasing age.

3. Size distribution measurements on the Chickens material showed a rapid growing period in the spring, followed by cessation of growth for the rest of the year. There is a correlation between amount of growth in a given year, and the sea temperature. On the Breakwater the males and females grow at slightly different times of year.

4. Concentric pigmented rings are demonstrated in the test, and are shown to be annual. They are used for estimating the growth rates on the different grounds, which are compared.

5. The duration of life is four to eight years, and perhaps more in the very large southern urchins.

On the rocky shores of the British Isles three species of Fucus are commonly found as components of the intertidal algal belt, namely, F. spiralis L., F. vesiculosus L. and F. serratus L. A fourth species, F. ceranoides L., occurs in places subject to the influence of fresh water but, although it may be important in connexion with the interacting processes to be described below, F. ceranoides is omitted from the present discussion because as yet too little is known of its autecology. Under the conditions prevailing in the characteristically zoned algal flora of an undisturbed region of a rocky coast, descriptions of the three species can be applied which fairly effectively distinguish one from the others. The chief characters used for this purpose are shown in Table I.

Red tides of the naked dinoflagellate Gyrodinium aureolum Hulburt occurred in sealochs in the north of the Firth of Clyde, Scotland, during late September 1980. Greatestconcentrations of the organism were found in the top 1 m layer of the water column, which was stabilized, and probably also enriched with nutrients, by freshwater input fromland drainage. In addition vertical and horizontal concentration must be postulated toexplain Gyrodinium cell densities of 2 x to7 cells I"1 and chlorophyll concentrations of 2228 mg m“”3 near the shore at Otter Ferry, Loch Fyne.

On 28 September 1980, water containing the red tide at Otter Ferry was unintentionally pumped into fish ponds at a shore-based salmon farm and resulted in the death, in one pond, of 3000 salmon each weighing about 1 kg and of 200–300 smolts in another when water was transferred to it from the affected pond. Pathological investigation of affected salmon showed that death was likely to have resulted from asphyxiation and osmotic shock as a result of extensive cellular damage to gills and guts. Results of mouse bioassays, using acidic and ether extracts of flesh and guts from affected salmon, suggest that necrotizing toxin(s) was associated with the cells of Gyrodinium aureolum during the bloom. The clinical signs exhibited by mice injected with toxin extracts were, however, unlike those caused by paralytic shellfish poison or toxins of the Gymnodinium breve type.

The locomotor roles of the myotomal muscles of fish are dependent on swimming speed. The mean maximum sustained swimming speed for coalfish (Gadus virens L.) during a 6-h period in an experimental exercise chamber was determined using a fixedvelocity technique and found to be 4 bodylengths/s. Biochemical measurements were made on the concentration of glycogen and lactate in the red muscle and white muscle at a series of known swimming speeds. Evidence is provided that red muscle alone is used at speeds below 2 bodylengths/s. The fall in concentration of red muscle glycogen was directly proportional to increased swimming speed. At speeds in excess of 2 bodylengths/s a statistically significant increase in lactate concentration occurred in the white muscle fibres. A reduction in glycogen content of the white muscle was also noted at speeds at and above the estimated mean sustained swimming speed. These results are discussed in the light of the current ideas pertaining to the division of labour between myotomal muscles in fish.

The impact of bottom trawling on cold-water corals (CWC) has been thoroughly studied and shown to be long-lasting; however the effects of bottom longlining on CWC ecosystems have received little attention. The present paper identifies the principal CWC species landed by bottom longlining in Faial (Azores) from 150 to 600 m depth. Data were obtained from a survey of 297 landings during four months coupled with 16 interviews with fishermen. A distinction was made among corals brought on deck directly entangled in the fishing gear (primary by-catch) from corals brought up associated with other larger CWC species or rocks (secondary by-catch). Forty-five (15.2%) of 297 fishing trips surveyed landed coral specimens. The survey recorded 39 different CWC taxa in the by-catch, belonging to five different orders (Scleractinia, Alcyonacea, Antipatharia, Zoanthidea and Anthoathecata). Secondary by-catch included a larger number of species but the total number of corals was in the same order of magnitude for both groups. The taxa most frequently encountered were Leiopathes spp., Errina dabneyiand Dendrophyllia sp. CWC taxa in the by-catch were mostly medium size (10–60 cm), 3-dimensional and branched colonies. Local ecological knowledge of fishermen confirmed that the corals recorded were representative of their past experience and also revealed a general agreement that there has been a decrease of CWC by-catch on traditional fishing grounds. Corals are common by-catch in bottom longline fisheries around the Azores and so conservation measures may be required.

Some sea cucumbers species are heavily exploited as bêche-de-mer for the Asian food industry and the global decline of certain highly sought after species has generated an interest in determining the ecological function of those animals within their ecosystem. This study investigated the ecological role of Holothuria scabra, a commercially valuable tropical species closely associated with seagrass beds. Seagrass productivity, seagrass and benthic microalgae (BMA) biomass and organic matter (OM) were measured during two exclusion experiments conducted using in situ cages deployed for two months both in 2003 and 2004. Density of H. scabra was manipulated in caged exclusions (near-zero density, ‘EX’), caged controls (natural densities, ‘CC’) and uncaged controls (natural density, ‘NC’). Seagrass growth was lower when holothurians were excluded (5% in 2003, 12% in 2004). Seagrass biomass decreased in all treatments, but reduction was greater in EX than in controls (18% in 2003, 21% in 2004). Both BMA biomass and OM increased in EX compared to NC/CC (in 2004). From a multivariate perspective, a principal component biplot separated EX from both types of controls in 2004, and multivariate tests based on four attributes supported this separation. These results indicate that seagrass systems may suffer in the absence of holothurians; however, the effect size varied between the two experiments, possibly because experiments were conducted at different times of the year. Nevertheless, our results suggest that holothurian over-fishing could have a negative impact on the productivity of seagrass systems.

Some of the most interesting and enigmatic cnidarians are classified within the hydrozoan subclass Trachylina. Despite being relatively depauperate in species richness, the clade contains four taxa typically accorded ordinal status: Actinulida, Limnomedusae, Narcomedusae and Trachymedusae. We bring molecular data (mitochondrial 16S and nuclear small and large subunit ribosomal genes) to bear on the question of phylogenetic relationships within Trachylina. Surprisingly, we find that a diminutive polyp form, Microhydrula limopsicola (classified within Limnomedusae) is actually a previously unknown life stage of a species of Stauromedusae. Our data confirm that the interstitial form Halammohydra sp. (Actinulida) is derived from holopelagic direct developing ancestors, likely within the trachymedusan family Rhopalonematidae. Trachymedusae is shown to be diphyletic, suggesting that the polyp stage has been lost independently at least two times within trachyline evolution. Narcomedusae is supported as a monophyletic group likely also arising from trachymedusan ancestors. Finally, some data, albeit limited, suggest that some trachyline species names refer to cryptic species that have yet to be sorted taxonomically.

The Blue Gym Initiative was created in the UK in 2009 to explore: (1) whether blue space environments might be positively related to human health and well-being; and (2) whether the public could be encouraged to preserve and protect these environments. Whilst the wider initiative considers all blue spaces including inland bodies of water (e.g. lakes, rivers and canals as well as the coasts and oceans), to date the focus has been primarily on marine and coastal environments. In this paper, we provide a brief history of the Blue Gym Initiative, and outline some of the research that has emerged to date. An important early finding was the observation that individuals living near the coast are generally healthier and happier than those living inland; much subsequent work has tried to understand why this might be. More recently we have begun to focus on how to promote pro-marine behaviours (e.g. sustainable fish choice, reduction of plastic use, avoidance of littering). This strand is still very much work in progress but highlights the importance of understanding public awareness, values and attitudes and the power of visualization in communicating the marine sustainability issues. We conclude with a brief discussion of some of the implications of the findings and future research needs.

The R, F and B cells of the hepatopancreas of Carcinus maenas are derived from undifferentiated (E) cells at the distal end of the tubules. Observations with the scanning electron microscope on freeze fractured tubules show that (a) most of the concentrically structured granules are confined to the R cells with few in F or B cells, (b) within individual R cells, granules are of similar size, and (c) the further R cells are situated from the distal end of the tubule, the greater is the mean diameter of the granules that they contain.

Measurements were made of the strength of temporary attachment of the cypris larvae of Balanus balanoides using a sensitive micro-balance. The strength of adhesion on arthropodin treated slate panels exceeded that on clean panels and the measured forces increased as the season progressed. The observed maximum cyprid attachment strength reached 3·8 × 105 N m−2, considerably less than the bond strength of a commercial epoxy adhesive (107 N m−2) but of the same order as the force required to remove limpets (Patella) from a slate substrate. The results are discussed in the context of substrate recognition by barnacle cyprids and the possible mechanisms of adhesion involved.

The work of Colebrook & Robinson (1965) has shown that there are three groups of seasonal cycle in production in the north-east Atlantic. There are three ‘races’ of herring in the same area, spawning in autumn, winter and spring. Taking the dates of spawning of each ‘race’ and the date by which the larvae must have food, a connexion can be made between the herring race and the production cycle in the area in which it lives. It is assumed that the date of spawning is fixed and does not vary with environmental conditions. Once the connexion between herring race and production cycle is made, certain comparisons can be made between races in growth rate, reproductive capacity and in the variability of recruitment. It was tentatively concluded that the magnitude of the year-class in the three north-east Atlantic races must be determined before metamorphosis. After metamorphosis, herring live on the beaches where the production cycle must have quite a different character.

Introduction

Herring populations have been grouped as spring and autumn spawners ever since they have been examined scientifically. Autumn spawners have been further subdivided into early autumn (or summer) and late autumn (or winter) spawners (Johansen 1924). Since the discovery of sharp differences in fecundity and egg size between early and late autumn spav/ners (Polder & Zijlstra, 1959), the distinction between them has acquired the same status as that between autumn spawners and spring spawners. However, there are very marked differences between all three groups, and to relate them to then-calendar times of spawning it is proposed to name then ‘ autumn’ (formerly early autumn), ‘winter’ (formerly late autumn) and ‘spring’ spawners.

Elasmobranch fishes cannot at present be aged by scale or otolith readings as can certain teleosts. Consequently comparatively little is known about their age or rate of growth, particularly in the case of larger sharks. Alternative methods of age determination within this group have utilized tagging data (Bonham et al., 1949; Holden, 1972); size frequencies (Olsen, 1954; Aasen, 1966); the spine of Squalus sp. (Kaganovskaia, 1933; Holden & Meadows, 1962); tooth-replacement rates (Moss, 1967, 1972) and vertebral rings. These rings on the vertebral centra, resulting from variations in calcification, have also been used in the age determination of teleosts. In the scombroids there is often considerable variation in results even between authors working on the same species, mainly due to difficulty in interpreting the rings and deciding whether they are true year marks (Aikawa & Katô, 1938; Partlo, 1955; Otsu & Uchida, 1959; Hui-chong, Nose & Hiyama, 1965).

Accounts of the ovarian development of the eggs of fishes have been given by Kisselevitch (1923). Mayenne (1927), and recently by Hickling (1930) and Raitt (1933). They have concluded that in the ovary of the adult fish there is a general egg-stock of small eggs, yolkless and transparent in fresh material, and with deeply staining cytoplasm in fixed and stained material. From this egg-stock a quota is withdrawn each year to be matured and finally spawned, and to this egg-stock a fresh batch is added each year by the development of oocytes present beneath the surface of the ovigerous lamellæ, the minimum period of development being two seasons.

It has occurred to us that measurements of the diameters of eggs, in ovaries well advanced towards spawning, may give evidence of the duration of spawning in a fish of which the spawning habits are unknown. For where the spawning period is short and definite, the batch of transparent yolkless small eggs, destined to mature and be spawned, will be withdrawn from the general egg-stock in a single group, sharply distinguishable, at least in the later stages of maturation, from the stock of small eggs from which it was derived. But when the spawning period is long and indefinite, the withdrawal of eggs from the egg-stock, to undergo maturation, will be a continuous process, and there will be no sharp separation between the general egg-stock and the maturing eggs. These will pass continuously one into the other. We have tested this hypothesis with four species of fish of known spawning habits.

The macrofauna of the intertidal mud-flats of the River Tamar have been investigated. Quantitative samples were taken by sieving the mud through a o·8 mm. sieve. Traverses of series of stations were worked at successive intervals up the river, and the tidal level of each station ascertained.

The characteristic species which inhabit the mud-flats are listed and the data secured regarding (1) population density, (2) up-river penetration, and (3) vertical distribution, are summarized and related to previous information on these points.

While some species are more or less uniformly distributed intertidally, others show marked zonation, with maxima in one part or another of the intertidal zone. Marine species which penetrate into the estuary tend to show the same intertidal distribution as in marine habitats. All five of the more strictly estuarine species are concentrated in the upper tidal levels.

In considering the limiting factors which cause a decrease of population at lower tidal levels, emphasis is placed on the probable importance of the increase in strength of water currents towards low water.

We describe the digenean fauna of one of the dominant intertidal hosts, the common cockle Cerastoderma edule, in terms of biomass, off north-eastern Atlantic shores. Using published and unpublished literature we have prepared an identification key and provide an up-date of the large-scale distributional patterns of digenean species of the common cockle. At least sixteen digenean species, belonging to seven families, use cockles as intermediate host. Among these species two utilize cockles as first intermediate host only, whereas two species utilize cockles as both first and second intermediate host. The remaining eleven species have cockles as their second intermediate host. Water birds and fish are the definitive hosts to twelve and four species, respectively.

Cockles are infected with digeneans along the latitudinal gradient from southern Morocco to the western region of the Barents Sea often with high infection levels. Whereas some of these digenean species occur along most of the latitudinal gradient others show a more restricted northern or southern distribution mostly caused by an underlying latitudinal gradient of host species.

Knowledge of digenean species and their large-scale distribution pattern may serve as a baseline for future studies dealing with the effects of climate change on parasite–host systems. For such studies the cockle and its digenean community could be an ideal model system.

Lasaea rubra is the smallest and commonest of Plymouth bivalves. It is intertidal on rocky shores, often in immense numbers, in crevices and other protected places, and in Pygmaea pumila (Colman, 1940). This bivalve is an excellent laboratory animal. It remains fully active for several days under laboratory conditions, and a large number of animals can be used in a single experiment, eliminating the variations in activity found when dealing with a few, or single specimens of larger animals. Because of the relatively high position Lasaea rubra may occupy on the shore its feeding cycle is broken by regular dry periods at each tide. Thus, for experiments relating to periodicity in feeding, we have an animal whose times of feeding can easily be ascertained and experimentally varied over a wide range. Lastly, in making serial sections and in examining total gut contents, in work on the digestive system, the small size of the animal is of obvious advantage.

We frequently require sensitive bioassay techniques with which to study the effects of marine contaminants at environmentally realistic concentrations. Unfortunately, it is difficult to achieve sensitivity and precision in an organism amenable to indefinite periods of laboratory culture. Results from different laboratories are often extremely variable: LC50 values for the same substance, using the same organism, may differ by two or even three orders of magnitude (Wilson, Cowell & Beynon, 1975). Moreover, some of the most sensitive bioassay organisms require nutrient media, which may alter the availability and toxicity of metals by complexing them (Jones, 1964; Kamp-Nielsen, 1971; Hannan & Patouillet, 1972) and often contain metal impurities at significant levels (Albert, 1968; Steeman Nielsen & Wium Anderson, 1970). The object of the work reported here has been to develop a technique by which these problems might be minimized or avoided. Hydroids were chosen as bioassay organisms for a variety of reasons. They are tolerant but sensitive to small variations in their chemical environment. Techniques for growing hydroids are simple and they can be cultured under conditions of near optimal temperature, salinity and food supply, thus minimizing the errors frequent in bioassay work arising from variations in the history of the test organisms, their size, sex or physiological state. An important source of variability in all work with organisms is that inherent in the genetic material, but with hydroids this can be avoided by the use of a single clone.

On the SOND Cruise of R.R.S. 'Discovery' in 1965 a day and a night series of horizontal hauls were made with a modified Indian Ocean Standard Net (N113 H) fitted with a catch dividing bucket (C.D.B.). The hauls were of 1 h duration, made at approximately 50 m depth intervals from 960 to 40 m, at a position off Fuerteventura in the Canary Islands. This paper is one of a series by various authors on the vertical distributions of the animal groups sampled (Angel, 1969; Clarke, 1969 a; Baker, 1970; Badcock, 1970; Foxton, 1970a, b). Details of the cruise and of the hydrology of the area are given by Currie, Boden & Kampa (1969), and Foxton (1969) gave details of the sampling methods.