|
Hi,
Are the right whales starving?
Jon Brodziak wrote:
>there
>are too many whales killed by injuries from entanglements with
>fishing gear (longlines to hold trap gears) and by vessel collisions
>for there to be any population increase.
>While it is possible that food limitation is an issue for right whale
>survival, I doubt it is an important effect compared to human-induced
>mortality. But I would be happy to reconsider this opinion if
>demographic data show otherwise. Please, show me the data.
>
Andrew Remsen wrote:
>Woods Hole Oceanographic scientists have modeled the survivorship of the
>right whale and concluded that survival has steadily declined for
>individual whales and population growth rate is negative. They concluded a
>major reason the right whale is declining is entanglement with fishing gear
>and collisions with ships. Additionally, their low numbers may have allowed
>competitors such as sei whales, mackerel or herring to move into right
>whale feeding grounds. Plus, their very slow reproductive rate and
>extremely small population size makes them extremely vunerable to any sort
>of natural fluctuations in prey distribution and abundance in addition to
>any human induced stresses. To use such a popuation as an index for
>plankton health in the north atlantic is a stretch.
>
>
Entanglement in fishing gear and collisions with ships - these are
consistently given as the two main reasons for the decline of the right
whale. I've followed the reports of the EWS survey crew for a couple of
years. Considering how few calves they see, it is not uncommon for them to
report seeing dead ones. Causes of death in the calves are generally
"undetermined" (fishing gear and ship strikes are very easily ruled out).
Here is a quote from the report filed by EWS in late February regarding the
inshore population of right whales: "...the worst calving season since
systematic monitoring of the population began almost twenty years ago...in
recent years many of the inshore animals have shown signs of what may be
malnutrition - poor skin condition, sometimes characterized by discolored
fungal-like swaths and lesions on the skin. Often these inshore animals
just don't look as fat..."
>If right whales have less food, then their population will decrease.
>We observe that the population has decreased, therefore they have
>must have had less food.
>This is a logical fallacy that reasonable people should avoid.
>
My "observation" is not only of a decreasing population, but of clear
clinical signs of malnutrition. The survey crew sees sick whales - these
animals are not "entangled" and have not been "struck" so the two main
"causes of the decline" do not come into play in this case. Also, why are
whales who have had no contact with ships or fishing gear unable to
conceive or maintain pregnancies? Something else is going on.
Another thought - starving people and animals become weak and
apathetic...and probably thereby more vulnerable to accidents like fishing
gear entanglement and ship strikes. It could be a factor.
"Their low numbers may have allowed competitors such as sei whales,
mackerel or herring to move into right
whale feeding grounds?" -- sei whales? how abundant are they?...and their
feeding strategy is different. Mackerel and herring in the Northwest
Atlantic (based on DFO stock status) do not appear to be increasing in
abundance. (Herring: landings and biomass estimates decreasing. Mackerel:
landings in decline.) This is very speculative, with very doubtful
evidence...I think it is "a stretch."
Debbie MacKenzie
http://www.fisherycrisis.com
><> ><> ><> ><> ><> ><> ><> ><> ><> ><> ><> ><> ><> ><> ><> ><>
To leave the Fish-Sci list, Send blank message to:
mailto:[log in to unmask]
Vacation? send SET FISH-SCI NOMAIL to [log in to unmask]
><> ><> ><> ><> ><> ><> ><> ><> ><> ><> ><> ><> ><> ><> ><> ><>
|
