Why does the endangered West North Atlantic whales grow slower than whale-hunting whales in the south, while a species of hunting dog avoids the risk of extinction by commercial whaling?
NOAA Aquaculture researchers and colleagues have a closer look at this question, and it is the most effective way to protect the lives of adult females in the population and promote population growth and recovery. Most of these deaths are attributed to confusion in combat vehicles and ships. Results have been reported Royal Society Open Science.
"The right-wing whales in the North Atlantic had increased at an annual rate that we were capable of. They would have almost doubled the population number in the present form, and their current situation would not be so terrible," says Peter Corkeron, paper and NOAA Fisheries Northeast Fishing Science Center & # 39 Great whale-headed research efforts.
The North Atlantic right whale, Eubalaena glacialis, is one of three species of right whales. The three live in the most industrialized habitat and migrate near the shore.
From 1970 to 2009, the cause of the 80 percent (87) of all North Atlantic right whale deaths was known, mainly due to fish hunting and collisions with ships. origin. In comparison, most of the observed southern right whales were calves in their first year of life, and very few could be directly attributed to human activities.
Calving Rates Are A Measure
"We investigated four populations of right whales, three of which were eastern whales, south Africa and southwestern Australia, and three of the southern parts of the southwestern North Atlantic population. It had comparable time series data and a minimum number of calves born each year," Corkeron said. "The intense aerial research of the North Atlantic right whale race habitat began in 1992, so it marked the beginning of our comparison."
The researchers compared the number of calves from 1992 to 2016 for each of the four populations. With this index, the annual growth rate of the North Atlantic right whales (about 2 percent per year) was much less than that of southern whales (between 5.3 and 7.2 percent per year).
Estimate the Internal Growth Rate of the North Atlantic Right Whales
The researchers then considered that this difference in the annual increase was due to human-induced injuries and deaths rather than ecological growth rates for each population.
They created a population projection model for the North Atlantic right whales, using the highest survival estimates obtained from the latest living analyzes using photo definitions and assuming four years between births. This resulted in an internal increase rate of approximately 4 percent, observed approximately twice.
The model results also showed that the deaths of adult females account for about two-thirds of the difference between the estimated internal growth rate and those observed.
The researchers also examined other factors and differences in the North Atlantic and southern populations. Eighty-three percent of all individual North Atlantic right whales are hunted at least once in their lives, and 59 percent have been confused two or more times.
Energy demands from entanglement can reduce the possibility of a female to reproduce successfully. The years between years of birth, months and years between the physical costs of entanglements can be taken into account the recovery period needed, increases in women. By comparison, fishing rods are almost absent for the south right whales.