spawning of bluefin tuna in the black sea historical evidence, environmental constraints and population plasticity产卵的蓝鳍金枪鱼在黑海的历史证据,人口环境约束和可塑性.pdf

Spawning of Bluefin Tuna in the Black Sea: Historical Evidence, Environmental Constraints and Population Plasticity 1 2 Brian R. MacKenzie *, Patrizio Mariani 1 Center for Macroecology, Evolution and Climate, National Institute for Aquatic Resources (DTU Aqua), Technical University of Denmark, Charlottenlund, Denmark, 2 Center for Ocean Life, National Institute for Aquatic Resources (DTU Aqua), Technical University of Denmark, Charlottenlund, Denmark Abstract The lucrative and highly migratory Atlantic bluefin tuna, Thunnus thynnus (Linnaeus 1758; Scombridae), used to be distributed widely throughout the north Atlantic Ocean, Mediterranean Sea and Black Sea. Its migrations have supported sustainable fisheries and impacted local cultures since antiquity, but its biogeographic range has contracted since the 1950s. Most recently, the species disappeared from the Black Sea in the late 1980s and has not yet recovered. Reasons for the Black Sea disappearance, and the species-wide range contraction, are unclear. However bluefin tuna formerly foraged and possibly spawned in the Black Sea. Loss of a locally-reproducing population would represent a decline in population richness, and an increase in species vulnerability to perturbations such as exploitation and environmental change. Here we identify the main genetic and phenotypic adaptations that the population must have (had) in order to reproduce successfully in the specific hydrographic (estuarine) conditions of the Black Sea. By comparing hydrographic conditions in spawning areas of the three species of bluefin tunas, and applying a mechanistic model of egg buoyancy and sinkin