During the period from April to September for the years 2014–2016, 998 swordfishes caught by the Moroccan artisanal longline fishery in the Strait of Gibraltar were sampled to study the reproduction of this species in this mixing area between the Mediterranean Sea and the North Atlantic. The results showed that the sex ratio is slightly in favour of males for sizes smaller than 130 cm LJFL (Lower jaw-fork length), whereas females are more numerous in sizes larger than 140 cm LJFL. Fifty per cent of females were estimated to be mature at 170 cm LJFL, while for males, the size at first maturity was estimated to be 95 cm LJFL. The swordfish spawn from June to September, probably in the Mediterranean Sea. The findings of this study suggest that the reproductive characteristics of swordfish caught in the Strait of Gibraltar are similar to those of the Mediterranean swordfish, and a high mixing rate between the Mediterranean and the North Atlantic stocks occurs in the study area.

The Antarctic plunderfishes Artedidraco lönnbergi and A. skottsbergi are small, bottom dwelling species inhabiting the continental shelf of the High Antarctic Zone. During cruise 97–9 of the US RV Nathaniel Palmer during the summer in the south-western Ross Sea, samples of both species were collected by means of bottom trawling. On the basis of macroscopic and histological analysis, we present the first data on the reproductive characteristics of these two plunderfishes, including gametogenesis, spawning period and absolute fecundity. Histologically, we found immature (stage I and II) and mature (stage V) females in both species, whereas developing females (stage III) were found only in A. skottsbergi. All examined male specimens of A. skottsbergi were in the final stage of spermatogenesis (stage III), whereas male A. lönnbergi were immature (stage I), mature (stage IV) and post-reproductive (stage V) individuals. In both species, spawning takes place in summer during December and January. Absolute fecundity was very low, with less than 100 and 200 oocytes in A. lönnbergi and A. skottsbergi, respectively. These data are compared with those reported in literature for other artedidraconids.

Reproductive characteristics are compared of the nototheniids Trematomus bernacchii and T. hansoni and the channichthyid Chionodraco hamatus caught in summer at Terra Nova Bay (Ross Sea) and caught all the year round in the waters off Casey Station (Mawson Sea). Whilst spawning of T. bernacchii took place in October–November off Casey and probably at Terra Nova Bay, the spawning period of T. hansoni differed between the sites (September–November off Casey, December–February at Terra Nova Bay). The spawning period also differed between sites for C. hamatus (August–October off Casey, December–February at Terra Nova Bay). Fecundity was higher and egg size was lower in nototheniid species (c, 8000 eggs of 3–4 mm) than in channichthyid (c. 4000 eggs of 4–5 mm). Moreover, the fecundity was lower and egg size higher in the specimens from Terra Nova Bay when compared to Casey.

We studied the reproductive biology of the lesser sandeel, Ammodytes marinus, on the fishing grounds of the east central North Sea and on an unfished ground off the coast of southwest Norway. As in other parts of the North Sea, gonad growth appeared to start in September and spawning occurred in December-January. Based on data from the spawning period, maturity ogives by length and age were derived. The length and age at 50 % maturity was 14 cm and 3.2 years respectively in both study areas. The age estimate is 1 year higher than that found previously in the southern North Sea and adopted for the ICES-assessments of the North Sea spawning stock. Estimates of fecundity appeared higher in the North Sea than in coastal waters, at least for large fish. The coastal water estimates also seemed low compared with fecundity at length relationships previously published from Shetland, Fair Isle, and Dogger bank. The sex ratio seldom deviated substantially from the 1:1 ratio, but in summer there appeared to be a surplus of females. Due to spatial differences in age-structure, the proportion of adults was generally much lower on the fishing grounds of the North Sea proper than on the unfished coastal ground. In the middle of the spawning period, however, aggregations of adults occurred on the North Sea grounds.

Two female barbel Rarbus barbus (L.) were tagged with implantable radio transmitters and tracked in the Ourthe River (Southern Belgium) from April 12th to July 7th, 1989 to study their movements and activity rhythms during the spring-summer period. Both barbels defined a 1.6 km home range and occupied four residence areas. Greatest average daily movements within the home range limits occurred during the prespawning and spawning periods and were associated with variations of mean daily water temperature and level. Barbel 2 made a 9.6 km excursion from its spring home range and homed a week later in its residence area. Barbels displayed dusk and dawn activity patterns, character- ized by the occupation of riffle areas. The activity timing was found to be dependent on water temperature while the size of daily activity area was more influenced by river flow conditions.