Baltic Sea populations of the northern pike (Esox lucius) have declined since the 1990s, and they face additional challenges due to ongoing climate change. Pike in the Baltic Sea spawn either in coastal bays or in freshwater streams and wetlands. Pike recruited in freshwater have been found to make up about 50 % of coastal pike stocks and to show natal homing, thus limiting gene flow among clos...

The reproductive pattern of Loligo vulgaris and Loligo forbesi was studied on the basis of gonad maturation, mating and spawning in males and females of both species which were present off the northwest coast of Spain (Galicia), between February 1991 and February 1993. The mature females of both species have several modes of egg sizes and developmental stages within the ovary. Several signs ind...

An attempt was made to provide some vital aspects of reproductive biology of cobia Rachycentron canadum (Linnaeus, 1766). Samples for a period of two years from an exploratory vessel and from the landing centers of Mumbai were used for the study. The average sex ratio between males and females observed was 1:0.80. Dominance of the number of females above the size of 100 cm was noticed. The size...

A study was undertaken to examine secondary sexual characters (spawning colouration and overall body size) in relation to sperm metrics in one alternative reproductive tactic of coho salmon Oncorhynchus kisutch: large hooknose males that spawn in dominance-based hierarchies. Males with less intense red spawning colouration had higher sperm velocities than males with darker red spawning colourat...

The spawning season of the tonguefish Syacium ovale (Günter 1864) was determined by an analysis of the distribution of preflexion stage larvae in the Gulf of California. The larvae were collected during eight oceanographic surveys between 1984 and 1987. The spawning of this species starts in early summer and ends at the beginning of fall, with the highest reproductive activity in mid summer. Th...

abstract reproductive biology of female shemaya (alburnus chalcoides) studied with examination of histology, egg diameter and value of sex steroid hormones during spawning phase in the anzali wetland from march 2013 to jun 2014. finally 42 numbers of female fish were examined. the result of sex steroid hormones showed the rate of testosterone hormone in gravid fish was 7.93±1.18 ng/ml; but in r...

For many corals, the timing of broadcast spawning correlates strongly with a number of environmental signals (seasonal temperature, lunar, and diel cycles). Robust experimental studies examining the role of these putative cues in triggering spawning have been lacking until recently because it has not been possible to predictably induce spawning in fully closed artificial mesocosms. Here, we pre...

Atlantic sturgeon (Acipenser oxyrinchus oxyrinchus) experienced severe declines due to habitat destruction and overfishing beginning in the late 19(th) century. Subsequent to the boom and bust period of exploitation, there has been minimal fishing pressure and improving habitats. However, lack of recovery led to the 2012 listing of Atlantic sturgeon under the Endangered Species Act. Although ha...

Since inferring spawning areas from larval distributions in the Sargasso Sea a century ago, the oceanic migration of adult American eels has remained a mystery. No adult eel has ever been observed migrating in the open ocean or in the spawning area. Here, we track movements of maturing eels equipped with pop-up satellite archival tags from the Scotian Shelf (Canada) into the open ocean, with on...

1. Temporal variation in the spatial aggregation of the freshwater bivalve Elliptio complanata was studied at a sandy site in an oligotrophic lake over three years. 2. Epibenthic populations varied in aggregation over the season bringing animals closer together during spawning. The complex link between movements of mussels and aggregation dynamics suggested a functional reproductive role for ho...