Many large groupers form spawning aggregations, returning to the same spawning sites in consecutive spawning seasons. Connectivity between spawning aggregations is thus assured by larval dispersal. This study looks into the genetic structure and gene flow among spawning aggregations of a large grouper, the gulf coney Hyporthodus acanthistius, in the northern Gulf of California. First, using the...

Sex steroids have long been known to exist in molluscs, but few studies have focused on the roles of these substances in molluscan reproduction. In this study, we demonstrate that injections of estradiol into ripe sea scallops induced spawning in both sexes, testosterone injections induced spawning in males only and progesterone blocked spawning in both sexes. We also show that injections of se...

The effects of castration on male spawning behavior, nestbuilding and fertility were measured in a five day spawning trial with an intact female. Spawning and fertility decreased one week following castration while nestbuilding was unaffected. Sham operated males showed normal spawning and fertility. Two weeks postoperatively, fertility and spawning were increased paralleling partial regenerati...

BACKGROUND Many fishes are known to spawn at distinct geomorphological features such as submerged capes or "promontories," and the widespread use of these sites for spawning must imply some evolutionary advantage. Spawning at these capes is thought to result in rapid offshore transport of eggs, thereby reducing predation levels and facilitating dispersal to areas of suitable habitat. METHODOL...

In this collaborative research project, we formed a partnership of commercial fisherman and scientists from UNH and NYU to investigate stock definitions for Atlantic cod using DNA markers. Cod in U.S. waters are currently managed as two stocks: 1) a Gulf of Maine stock and 2) a Georges Bank and south stock. This designation is decades old and warrants reevaluation in light of concerns that fish...

Temperature is often an important variable influencing the vertical position of fish larvae in water column. The same species may show different distributions areas with a strong near-surface seasonal thermocline compared to isothermal regions. In surface thermocline, tuna significant preference for warmer layers. Little known regarding larval distribution waters and on associated assemblages. ...

Recent studies have shown that warm temperatures reduce survival of adult migrating sockeye salmon (Oncorhynchus nerka), but knowledge gaps exist on where high-temperature-related mortality occurs along the migration and whether females and males are differentially impacted by river temperature. In this study, we monitored 437 radio-tagged Fraser River sockeye salmon and used capture–mark–recap...

Introduction Atlantic bluefin tuna (ABT) are large, migratory pelagic predators of high economic importance. ABT currently managed as two independent stocks assigned to discrete spawning areas (Gulf Mexico, and Mediterranean); however, stock overlap outside makes accurate assignment catch stock-of-origin difficult. Methods Within this two-stock paradigm, we characterised stock-specific spatial ...

This study analysed the temporal pattern of Atlantic bluefin tuna (ABFT) spawning in the Balearic spawning ground and examined its reproductive performance after years in captivity. Furthermore, ABFT hatching time at different on-site temperatures was determined for the first time. Spawning surveys were carried out in 4 spawning seasons (2009-2012) aboard tuna transport vessels. Three groups of...