Shell growth of the razor clam Ensis siliqua (Mollusca: Bivalvia) from southern Portugal has been analysed using both surface growth rings and internal shell microgrowth patterns. The growth rate estimated from an analysis of the growth rings is slower (von Bertalanffy growth, constant K=0·27) than that determined from the annual narrowing of the internal microgrowth patterns present in shell sections (K=0·65), although both methods predict a similar asymptotic length, L∞, of 144·8 and 139·6 mm, respectively.

The Barrinha razor clam population occurs in a heavily dredged area and an analysis of shell sections reveals the presence of a series of shell margin breaks consisting of deep clefts in the outer shell layer in which sand grains are embedded. It is suggested that these disturbances to shell growth are the result of repeated dredge damage. The frequency of the clefts increases with the size and age of the razor clams, and thus the shells provide a record of the intensity and frequency of unsuccessful capture or retrieval attempts. Cleft formation also occurred seasonally with the deposition of a small cleft during June, but these annual clefts were much less pronounced than those caused by dredge damage.

The concept of external metabolites in the sea, which has received support from biological investigations, invites chemical corroboration which, until recently, has not been forthcoming. Separations of organic matter from filtered sea water using a variety of methods are reported and a preliminary assessment made. Organic residues obtained from different open sea sources by adsorption on carbon give rise to different paper chromatogram patterns. Certain organic components of a carbon adsorbate contain substances which affect the growth of a number of marine phytoplankton organisms. Further research is planned employing methods of isolation and chromatography of the dissolved organic matter from different sea waters and the assessment of biological activity of certain fractions by means of common marine organisms. Some aspects of the significance of biologically active compounds in the sea are mentioned.

This study used Monte Carlo methods to generate simulations that considered the effort distribution to determine the locations of significant aggregations of cetacean sightings inside the northern Pelagos Sanctuary (north-western Mediterranean Sea). For three years, monitoring has been conducted from five motor vessels covering about 30,050 km. The most frequently encountered species were the striped dolphin Stenella coeruleoalba representing 64.7% of all sightings, the fin whale Balaenoptera physalus (17.0%), Cuvier's beaked whale Ziphius cavirostris (9.9%), Risso's dolphin Grampus griseus (4.3%) and the sperm whale Physeter catodon (2.2%). Sightings' positions and effort coverage were distributed over a grid of 5′ longitude and 5′ latitude. Spatial concentrations of sightings were analysed according to the distribution of effort to identify ‘hotspots’ (locations where the species occurred at a significantly greater frequency than expected), and ‘coldspots’ (locations with a significantly lower frequency than expected). Most fin whale hotspots (14) were located on the bathyal plain between 2000 and 2500 m, four hotspots were around the 1000 m isobaths, and one is located close to the seamount off Genoa. Fin whale coldspots were mainly along the coast. Striped dolphin hotspots were widely distributed over two main areas, in waters with depths between 2000 and 2500 m and at the continental slope; coldspots for this species were also mainly along the coast in the northern part of the study area. Many hotspots were found in the Genoa Canyon, and hotspots of striped dolphins, Cuvier's beaked whales, sperm whales and Risso's dolphins overlapped in this region. Some of the hotspots of Cuvier's beaked whales were identified at the seamount in the study area, where no other species was sighted frequently. Risso's dolphin hotspots were mainly near the 1000 m isobath. For sperm whales, several hotspots were identified: three associated with steep slope features (such as canyons or the continental slope), and one was in the centre of the flat area of Pelagos where the depth is 2500 m. This study highlights the ecological importance of particular locations inside the Pelagos Sanctuary—locations that should be protected from anthropogenic degradations for marine mammal conservation.

This study investigated factors affecting the metabolic rate of Cancer pagurus eggs. The oxygen uptake of portions of the egg mass and recently hatched zoeae was measured. Oxygen uptake of the eggs of an individual animal was found to vary widely, with measured mean values under normoxic conditions ranging from 38 to 250 μmoles O2 kg−1 min−1. Mean values for the oxygen uptake of zoeae ranged from 958 to 1168 μmoles O2 kg−1 min−1. Mean rates of oxygen uptake of the eggs generally increased with increasing seasonal temperature and advancing developmental stage. Rates of oxygen uptake were maintained over a wide range of ambient oxygen partial pressures. As oxygen partial pressure in the seawater surrounding the eggs fell from a critical value (Pc) of between 60 and 90 mm Hg, the oxygen uptake of the eggs also declined. Mean values for ambient oxygen partial pressures within the egg mass in vivo ranged from 34 to 98 mm Hg. Adult female C. pagurus appear to be able to detect conditions within the egg mass and adjust their egg ventilation behaviour accordingly. Active egg mass ventilation by the adult increased as the eggs became more developed and their oxygen demands increased.

Samples of female lllex argentinus were taken from the catch of a Japanese squid jigging vessel on the Patagonian Shelf during March 1986. Morphometrics of the somatic and reproductive organ systems and the histological structure of the mantle in relation to maturation were examined. The data suggest that growth and maturation occur simultaneously during most of the time that lllex argentinus females are on the feeding grounds. In a squid of a ‘standard’ mantle length the whole body mass increases relative to mantle length during maturation and growth of the reproductive organs. This is accompanied by a small but significant decrease in the relative mass of the mantle, head and viscera whilst the mass of the digestive gland remains constant. Although mantle mass of a ‘standard’ female squid decreases relative to mantle length with maturity this is not associated with degeneration of the mantle muscles. Energy and nutrient resources for maturation are apparently derived from the squid's food, not from reserves, and during the course of maturation there is an increasing shift of emphasis from somatic growth to production of gonad and accessory reproductive organs.

Seasonal changes in the diet of the Atlantic mackerel from the north-east Atlantic in ICES Division VIIIc during the period 1988–1999. The diet of juvenile (21–29 cm) and adult mackerel (30–45 cm) in this area in spring (the spawning season) and autumn varied in composition and size of prey. In spring, the average prey weight was 0·009 g and the number of prey was 180 individuals per stomach, with the average stomach content volume being 1·62 g (0·60% BW [body weight]), and 1·50 g (0·51% BW) when considering the empty stomachs. In autumn, the average prey weight was 0·28 g, the average number of prey per stomach was 17, and the average stomach weight that contained food was three times higher than in spring, and 2·3 times when considering the empty stomachs. In spring, the diet of the juveniles consisted of euphausiids, crustacean larvae and other zooplankton, whereas euphausiids formed 90% of the diet in the adults. In addition, during this period mackerel were cannibalistic, feeding on their own eggs. In autumn, the juveniles ate hyperiids and other, mainly gelatinous zooplankton, whereas for the adults blue whiting were clearly important, since they comprised 90% of the stomach weight.

In this work, we evaluated the influence of long rocky jetties (~5 km) on fish abundance and diversity between sheltered and exposed marine sandy beaches. We also described and compared the fish community structure and investigated the relationships between environmental variables and fish assemblages. Fish were collected monthly with a beach seine net from May 2001 to May 2002 at the Cassino and Mar Grosso beaches. Twenty-nine taxa were caught and the fish assemblage showed similar composition between beaches (Sj = 62.1%; %Min = 52.3%), with 18 species in common. Most of the fish were juveniles, mainly young-of-the-year with sizes ≤60 mm total length. Eight species (Trachinotus marginatus, Mugil liza, Brevoortia pectinata, Menticirrhus littoralis, Menticirrhus americanus, Odontesthes argentinensis and Oncopterus darwinii) were the most abundant, accounting for 95.6% of the total catch. At both beaches, only T. marginatus, M. liza and M. littoralis were frequent and abundant, but with some differences in their relative abundance. The canonical correspondence analysis results showed that temperature had the highest correlation with fish abundance. Seasonal changes in fish assemblage structure were evident, with a greater species diversity and abundance in the spring and summer. The overall results indicate that the presence of jetties had no effect on fish assemblages of adjacent sandy beaches. Moreover, differences between beaches were related to some species abundance and not to differences in the number and composition of species between beaches.

The annual cycle of silicate, nitrate and phosphorus in the waters of the Menai Straits is described. The concentration of all these nutrients in these waters is apparently markedly affected by occasional incursions of high-salinity low-nutrient water. The concentrations of nitrate-nitrogen tend to show a general increase throughout the winter months as a result of cumulative contributions from land drainage and run off and the absence of appreciable biological utilization. In contrast, an equilibrium concentration of reactive silicate is maintained over this period following the initial autumnal increase in the concentration of this component. The annual cycle of phosphorus in these waters is also anomalous. Relatively high equilibrium concentrations of this nutrient are maintained during the summer months and unexpectedly low concentrations occur in winter. In conjunction with the biological removal of relatively large amounts of nitrate-nitrogen, this causes anomalously high apparent N: P biological utilization ratios. It is difficult to explain the observed variations in the concentration of phosphate in these waters solely in terms of the equilibrium between biological assimilation and regeneration and advective processes.

Having been engaged at intervals during the last few years in studying from a physiological point of view the coagulation of crustacean blood—Tait (08), (10, A and B), (11)—and finding more variation in this regard in different Crustacea than has hitherto been recognized, it suggested itself to me to inquire if the observed differences are correlated with any special physiological peculiarities, and, further, if they depend in marked degree on phylogenetic relationship. It is not a simple matter to settle either of these questions, and I make no pretence to have done so. At the same time, I have thought it worth while to put my observations on record, in the hope that the matter may thus sooner arrive at a satisfactory settlement.

The hermit-crab, Eupagurus Bernhardus, is common in the oyster beds in the upper part of the Fal Estuary, and experiments indicate, while observations and experiments on the mode of feeding virtually prove, that these hermit-crabs do not harm healthy small oysters one inch or more in length, and the larger oysters, but that spat less than one inch may occasionally be damaged or eaten by hermit-crabs picking with their claws indiscriminately at growths on shells and stones.

E. Bernhardus obtains food largely by its small claw and third maxillipedes, and may at certain periods of the year feed mainly on microorganisms, and at others on macroscopic, but mainly tiny living organisms which have been disturbed and captured in the deposits on the sea-bottom. Food can be obtained by the use of the third maxillipedes alone.

If the number of infections with (a) trematode parthenitae and cercariae using Littorina neritoides as first intermediate host only, and (b) encysted metacercariae using L. neritoides as second intermediate host only, are plotted against the size of the snails, two different curves result. The first shows a low rate of infection in the small size groups, but a steep upward slope rising to 91% in the large size groups. The second shows a curve increasing uniformly to 87% infection.

Possible interpretations are discussed, and it is concluded that the difference is probably due to the fact that primary infections cause accelerated growth in the host.

Three species of copepods—Calanus finmarchicus (Gunnerus), C. helgolandicus (Claus) and C. hyperboreus (Krcyer)—can be easily and consistently differentiated by starch-gel electrophoresis of a number of their enzymes. The techniques used allow the study of individual variation in natural populations of small invertebrates, some of the variation being readily equated with known genetically based protein polymorphisms in man and other species. C. finmarchicus and C. helgolandicus have 15 enzyme zones in common and differ by 24-28 zones. By the rationale of molecular biology it can be suggested that these two forms differ in two-thirds of the structural genes. The results support the morpho-logical studies by Rees (1949) and Matthews (1966b) and the chromosomal studies by Harding (1963). Hence it is clear that the ‘finmarchicus-helgolandicus’ problem is solved: C. finmarchicus and C. helgolandicus are distinct species. The potentials and problems of biochemical systematics are discussed with particular reference to marine biology.

INTRODUCTION

Electrophoretic techniques have contributed to the solution of many taxonomic problems—for example, the monophyletic origin of ratite birds (Sibley, 1960), the discovery of a sibling species of sea-cucumber (Manwell & Baker, 1963 a; Manwell, 1966a), the status of species and populations of pheasants (Baker, 1965; Baker, Manwell, Labisky & Harper, 1966), the union of the orang-utan, chimpanzee, gorilla and man into one family, the Pongidae (Tashian, 1965), and the recognition of hybridization in lizards (Dessauer, Fox & Pough, 1962) and fishes (Manwell, Baker & Childers, 1963).

Killer whales have been described in the Gulf of Cadiz, southern Spain, in spring and in the Strait of Gibraltar in summer. A total of 11,276 cetaceans sightings coming from different sources (dedicated research surveys, whale watching companies and opportunistic observations) were used to create two presence–‘pseudo-absence’ predictive generalized additive models (GAM), where presence data were defined as sightings of killer whales and ‘pseudo-absence’ data as sightings of other cetacean species. One model was created using spring data when killer whales’ main prey, Atlantic bluefin tuna, enter the Mediterranean Sea, and the other model used summer data when Atlantic bluefin tuna return to the Atlantic Ocean. Both model predictions show that killer whales are highly associated with a probable distribution of bluefin tuna during their migration throughout the study area, constraining their distribution to the Gulf of Cadiz in spring and the Strait of Gibraltar in spring and summer. Knowledge of the distribution of killer whales in the study area is essential to establish conservation measures for this population.

Estimations of sodium, potassium, calcium, magnesium, chloride and sulphate have been made on the blood and muscle of marine molluscs and of the freshwater clam, Anodonta.

On comparing marine blood with sea water it appears that the cephalopods show a regulatory power (i.e. difference between blood and sea water) with respect to all ions tested except sulphate. The gastropods have a regulatory power for calcium, magnesium and chloride; the pelecypods for calcium and magnesium.

Calcium is always higher in blood than in sea water, while magnesium is lower. Chloride, where it differs, is lower.

If muscle is considered as two phases, cells and intercellular blood space, then from whole muscle and blood analyses it is possible to calculate the spaces between the cells, which work out at 11 % for pelecypods and 18 % for the other two groups. Further calculation gives the constitution of the cells themselves, leading to the conclusion that, of the ions under consideration, only K is present in the Pelecypoda and Cephalopoda, while the Gastropoda may have some Ca and Mg as well as K.

As expected the fresh-water clam contains little inorganic material. In relative proportions its blood is characterized by more calcium and less magnesium and chloride than that of marine forms. In muscle cells potassium dominates but other ions are present as well.

This work was carried out at the Laboratory of the Marine Biological Association, Plymouth, in the summers of 1936 and 1937, and at the Oceanographic Institution, Woods Hole, in 1939. It is a pleasure to express our thanks to the Directors and Staffs of these establishments for accommodation,facilities and advice during the progress of the investigation.

1. Monthly samples of Echinocardium cordatum were taken at Port Erin in 1932,1933 and 1934, and at intervals at Fairlie Sands in the Clyde.

2. Growth is continuous throughout the year with the exception of February-March. In their first winter the young urchins attain a length of about 10 mm. at Millport and 15–20 mm. at Port Erin. In their second winter they are about 20 mm. at Millport, and 30–35 mm. at Port Erin.

4. The year 1931 was cold and produced a very small brood of young urchins; 1932 and 1933 were warm years and produced very large broods.

5. The young settle below low water and migrate into the interval zone after an interval of four to twelve months.

6. The gonads of the young urchins mature in their second year. Spawning takes place in June–July–August.

7. The nutritive bodies in the ovaries are shown to be derived from the disintegration of relict ova.

The T-POD (Timing POrpoise Detector) is a self-contained acoustic data logger used for detecting and monitoring the presence of echolocation clicks of small cetaceans. It has become a standard tool in environmental impact assessments and monitoring programmes. Yet, little is known about the variability in sensitivity and detection range of T-PODs. In this study the field performance of ten v3 T-PODs was compared to detection thresholds measured in a tank. The T-POD thresholds ranged from 123 to 132 dB re 1μPa (pp). The detection thresholds of the ten individual T-PODs were different and the differences increased over time. The more sensitive a T-POD was in the laboratory (i.e. the lower the threshold) the more clicks were recorded by it in the field. Threshold correlated differently to the five analysed T-POD parameters (encounters, encounter duration, waiting time, porpoise positive minutes, clicks per porpoise positive minute). This study demonstrates that individual threshold calibrations of T-PODs are necessary to obtain comparable results when monitoring odontocetes with this tool. Regression equations for relationships between T-POD detection thresholds and study parameters obtained during field trials may allow comparisons of T-PODs with different detection thresholds.

The biochemical composition of three batches of Ostrea edulis L. spat was determined during post-settlement growth. The spat were from spatfalls in January, March and June. For the first few months after settlement the neutral lipid (triglyceride) content was greater than the glycogen content. However, in three- to five-month-old spat the glycogen content became greater than that of neutral lipid.

Using the mouse bioassay for paralytic shellfish poison (PSP), the distribution of toxicity among 23 dinoflagellate species was studied. Special consideration was given to red-tide-forming species and to those species previously implicated as causative organisms in paralytic shellfish poisoning. Among those investigated were ten marine species of the genus Gonyaulax, previously known to contain three toxic species. The presence of PSP was detected only in Gonyaulax species of the section Catenella. The amount of toxin varied in different species, ranging from 0.05 to 24 pg/cell. The amount of toxin per cell also varied with the phase of growth (exponential or stationary) in the New England red-tide species, G. tamarensis var. excavata Braarud.

Eurydice pulchra Leach is a common intertidal isopod of sandy beaches. Its occurrence around the British Isles has been described by Jones & Naylor (1967), and Salvat (1966) has described the life cycle and intertidal distribution of the species on the west coast of France. There are several records of its intertidal distribution in Britain (Elmhirst, 1931; Pirrie, Bruce & Moore, 1932; Rees, 1939; Watkin, 1942; Brady, 1942; Holme, 1949; Southward, 1953; Colman & Segrove, 1955; Perkins, 1956; M. Ladle, unpublished) and these suggest that its distribution is variable. Watkin (1942) found that the population structure of E. pulchra in late March and early April was comprised of ‘two distinct groups’ and similar findings were made in July by Scott (1960). The present study was made on a large intertidal population in the sands of the Dovey Estuary, Cardinganshire.

Results from the Continuous Plankton Recorder survey were used to study long-term changes in the zooplankton of four regularly sampled areas of the North Sea. The trends in α-diversity are described and analysed. Species associated with inflow of oceanic or mixed waters from the Atlantic or shelf to the west and south of Britain have increased in abundance or frequency of occurrence. Meroplankton have also increased but resident holoplankton and those associated with colder oceanic or mixed waters have declined. These changes have resulted in an increase in the species richness in the areas in the north-western North Sea. There was a period of low diversity in the late 1970s and early 1980s in the most southerly area, furthest from the sources of inflow. The evidence for a long-term trend was stronger than relationships between diversity and either the North Atlantic Oscillation or variation in position of the Gulf Stream in the western Atlantic.