The reproductive cycle of Zygochlamys patagonica was studied from October 1999 to February 2001 in a bed located in the south-western Atlantic (Reclutas bed 39°24′ S–55°56′W). Scallops were collected monthly and the sexual maturity stages were determined histologically (N = 508). Sex-ratio was 1:1 (t-test P > 0.05). The size of first sexual maturity was estimated from males of an average of 36.63 mm and females of 36.31 mm of shell height. The relative gonadal condition index (RGCI) showed an annual cycle, with higher values during winter–spring and lower values during summer–autumn; an inverse relationship for the relative muscle condition index (RMCI) was observed with maximum values in early summer. Thus, a reallocation of energy from soma to gonad appears to be inevitable to meet energy demand of gonad development. Seven histological stages of sexual maturity were established for both sexes: (1) immature; (2) early maturity; (3) advanced maturity,;(4) ripe; (5) spawning; (6) spent; and (7) recovery. Individuals in early and advanced maturity were found throughout the year; however, they were found more frequently between June and September. Spawning began in October (early spring) and extended through March (late summer–early autumn) coexisting with early and advanced maturity stages supported by the annual variation of the RGCI and the food availability into the system.

In a field survey and a field experiment the relative importance of host size and temporal exposure in determining metacercarial infection levels in an intertidal bivalve was investigated. While cockles (Cerastoderma edule) of different age (indicated by winter rings on shells) collected at the same site showed strong positive correlations between host size and infection levels over the total sample, correlations were weak or absent within the age groups. Mean infection levels in cockles strongly increased with age suggesting temporal exposure and not size to be the main determinant of infection levels in the cockles. This was supported by a field experiment in which small and large cockles were exposed for one or two months on a tidal flat. While infection levels significantly increased with temporal exposure, host size had no significant effect. This suggests that bivalve hosts on temperate tidal flats accumulate parasites during a distinctive infection window during summer more or less independent of their size. With every additional year of exposure, infection levels of the parasites increase. Hence, it is important to take host age into account when comparing individual infection levels within and among different host populations.

The genus Robsonella Adam, 1938 belongs to the family Octopodidae and can only be identified by some characters present in males. In this work the species Robsonella fontaniana is redescribed from morphological and morphometric characters of 33 specimens (21 males and 12 females) collected on the central-south coast of Chile, during the years 2003 and 2004, and of 11 specimens (three males and eight females) obtained from the Zoological Museum of Hamburg. New diagnoses for the genus Robsonella and the species R. fontaniana are provided. Sexual dimorphism in R. fontaniana is evident by adult males having enlarged suckers and a shorter third right arm compared to the females. Some morphological characters such as ligula, radula and terminal organ diverticulum make it possible to distinguish this genus clearly from other genera. The ligula of the hectocotylized arm in Robsonella is characterized by a longitudinal groove, rounded tip, large calamus and seven copulatory lamellae. In addition, the first lateral tooth in the radula is crescent-shaped; this allows the identification of Robsonella regardless of sex.

In both protected and fished rocky reefs in the southern Adriatic Sea, the behaviour of the sea breams Diplodus sargus and D. vulgaris (both targeted by spear-fishing) in the presence of divers was found to be mostly negative (i.e. escape response). However, at protected reefs sea breams frequently swam into the closest shelters, whereas in fished reefs they mostly escaped in open water. This study suggests that spear-fishing may alter the escape response of fish from natural predators and that marine reserves may re-establish natural behaviour patterns.

The reproductive biology of 1318 sand sole, Pegusa lascaris, was investigated. This species is a gonochoristic species with no evidence of sexual dimorphism. The overall sex-ratio was 1 male to 0.92 females. Females predominate in the larger size intervals, with a significant difference in mean standard length and range between sexes. Size at first maturity for males and females is attained at 17.2 and 17.7 cm standard length, respectively. Vitellogenesis does not begin synchronously for all females, as a consequence the spawning season appears to be continuous. In each female spawning takes place in two batches which are spawned mainly in spring and autumn, indicating that fish are serial synchronous spawners.

The life histories of Plecoglossidae and Osmeridae fish collected from Japanese fresh, brackish, and seawaters were studied by examining the strontium (Sr) to calcium (Ca) ratios in their otoliths. The Sr:Ca ratios in the otoliths changed with the salinity of the habitat. The fish living in a freshwater environment showed consistently low Sr:Ca ratios throughout the otolith. The fish were identified as a standard freshwater type. In contrast, fish collected from the intertidal zone showed higher otolith Sr:Ca ratios than those in the standard freshwater type, and the ratios fluctuated along the growth phase. In the present study, in addition to the representative migration pattern reported previously, other migration patterns were found to show consistently high Sr:Ca ratios throughout the otolith in several Osmeridae fish. Those results indicate that these fish have a flexible migration strategy with a high degree of behavioural plasticity and an ability to utilize the full range of salinity throughout their life history.

In order to determine if eastern Pacific green turtles (Chelonia mydas) exhibit feeding preferences samples of recently ingested food items were compared to the food resources available in the marine environment where C. mydas congregates. Stomach samples were collected by conducting gastric lavage and, at the same time, vegetation transects were conducted during spring and winter. Green turtles in our study selectively consumed seaweeds, with Codium amplivesiculatum and Gracialaria textorii as preferred species. Differences in the consumption of species were found across the two mentioned seasons and were consistent with changes in the availability of different algae species in the environment. Based on these results, it is recommended that sea turtle conservation plans along the Baja California Peninsula include Pacific coastal mangrove channels with a high diversity of algae species as priority areas for protection.