The breeding season of Nerophis lumbriciformis (Pisces: Syngnathidae), has not yet been determined for the southernmost part of its range. A total of 863 individuals was examined between March 1997 and November 1999. In Portugal, the breeding season of this species occurs throughout the year, with a marked reduction during summer and autumn, whilst in Britain it occurs from May to September. Despite these temporal differences, the water temperature at which breeding takes place is similar in the two areas (13–16°C). Together with preliminary laboratory observations with animals kept at different temperatures, these data support the hypothesis that the decrease in breeding activity during summer and autumn in Portugal is due to an inhibitory effect of high water temperature.

Ontogenetic and seasonal variations in the diet were studied for a benthopelagic fish, the red cod Salilota australis (Pisces: Moridae) from the Falkland Islands shelf. The study revealed that small fish (<39 cm total length, TL) fed mainly on benthic gammarid amphipods, with squid Loligo gahi, Illex argentinus and the fish Patagonotothen spp. being of secondary importance. In medium sized fish (40–60 cm TL) the importance of fish in their diet increased, but benthic gammarid amphipods remained important, although their role decreased in the percentage by weight. Large fish (>61 cm TL) fed mainly upon Patagonotothen spp. which consisted of 90% by weight. Seasonal variations were analysed only for medium-sized fish. In February–June, S. australis fed mainly on benthic amphipods and Patagonotothen spp. In July–October, the squid Loligo gahi became the most common prey. In November–January benthic crustaceans reappeared in the diet, and Patagonotothen spp. became the most important prey item followed by benthic gammarid amphipods and the isopod Seriolis sp. The niche breadth was found to be similar in the different size groups (2·03–2·66), indicating that the fish fed on one to two abundant prey items in each group. The niche breadth of medium-sized fish varied seasonally reflecting the diversity of prey items utilized throughout the year.

The diet breadth and diet overlap of two co-existing species of flatfish, plaice (Pleuronectes platessa) and dab (Limanda limanda) inhabiting a shallow bay in south-west Ireland are compared. They were shown to vary with the resource matrix, the gut region and the sample size. Diet breadth was calculated using Levin's index and diet overlap calculated using Horn's index. Values of diet breadth were considerably less for numerical abundance data when compared to percentage occurrence data. Similarly, diet overlap values were less for numerically derived data. In dab, diet breadths were significantly lower for stomach-only contents than for intestine-only or whole gut contents. In plaice, there were no significant differences in diet breadths between gut regions. Significantly lower diet overlaps for stomach-only data were also found. Reducing the size of sample to N=30 and N=10 resulted in increases in the calculated value of diet breadth, by as much as 0·13 and 0·34 respectively, these increases were frequently significant. The same reductions in sample size for diet overlap decreased overlap values by 0·02 and 0·13 respectively, significant only when sample reduced to N=10.

Ecological aspects of the marine tucuxi dolphin, Sotalia fluviatilis (Cetacea: Delphinidae), remain poorly known. Important information can be gathered in long-term studies using photo-identification. Using this methodology, the authors present the first evidence of site fidelity for marine tucuxis in the Cananéia Estuary (25°03′S 48°01′ W), south-eastern Brazil. A total of 86 easily recognizable individuals was catalogued from June 1996 to August 2001, but most of them have been sighted from May 2000. From June 1997 to August 2001, three female tucuxis were sighted on nine (KN #19), 22 (KN #30) and 28 (KN #10) different days in a relatively small area (∼16 km2). Each of them was observed with a calf in 1997–1998 and again with a new offspring in 2000–2001. Thirteen other individuals were reported on eight to 19 different days in the same area between May 2000 and August 2001. Our observations lead to conclusions on the evidence of site fidelity and indicate that calving intervals may range between two and three years for this species in the surveyed area.

The stomach contents of 16 bottlenose dolphins Tursiops truncatus (Cetacea: Odontoceti) stranded in the Spanish Mediterranean coast were examined. Remains and size of prey were analysed and correlated with the ecological characteristics and behavioural patterns of this dolphin. Fish and cephalopods represented the main diet components, and hake Merluccius merluccius was the most important prey. The food habits were considered as mainly demersal according to the characteristics of the prey. The study suggested ontogenic and sexual differences in feeding behaviour based on diet composition and hake size. The potential causative factors, particularly as they relate to dolphin social structure, are discussed.

Amphipod traps baited with crab carrion caught significantly greater numbers of the specialist crab necrophage, Orchomene nanus in the South Basin of Lough Hyne than in the North Basin. The results can be explained with reference to the known distribution of crab species in the lough and also the hydrographical characteristics of the two basins.

Evidence of sexual dimorphism in the mud-shrimp Upogebia stellata was observed in the abdomen length, total length, and also in the chelae. For the same carapace length, males had a shorter abdomen and, therefore, total length, whilst their chelae were larger and more robust than the females. Of the 91 U. stellata individuals examined, a single specimen was found to be of an intersex type, i.e. it exhibited both male and female external characteristics. Sexual dimorphism and intersexuality are discussed.

When the mean adult length and mean clutch volume of marine turtles are examined, a clear pattern for larger species to lay larger clutches is evident, in accord with predictions that female size constrains the available space for carrying eggs. However, when compared with this general trend, the volume of clutches laid by flatback turtles (Natator depressa) are smaller than expected. The implication is that the unusually flat morphology of flatback turtles, provides an additional constraint on their egg carrying capacity.

We challenge a conclusion reached by Barnes & de Villiers in a paper that was recently published in this Journal, viz that certain benthic invertebrates occur in lower abundances in lagoons than in intertidal soft-bottom areas and that this difference is due to lower food supply at lagoon bottoms. Our experience in the Wadden Sea shows that food does not limit the abundance of primary consumers in areas where environmental conditions are harsh. Such conditions prevail in most of the upper half of the intertidal which is characterized by low abundance of zoobenthos despite a high food supply.