Nav: Home

Immature spinner dolphin calf SCUBA tanks spell disaster in tuna fisheries

April 19, 2017

Just because dolphins are born in water doesn't necessarily mean that their in-built SCUBA system is fully prepared for action at birth; it can take between 1 and 3 years for the oxygen carrying capacity of whales and dolphins to mature sufficiently. Shawn Noren, from the University of California, Santa Cruz, USA, explains that the muscles of fully developed diving species - including dolphins, whales, birds and seals - contain more of the oxygen carrying protein, myoglobin, than land-based animals and are better prepared to neutralise lactic acid produced in the muscles when divers switch to anaerobic respiration after exhausting their oxygen toward the end of a dive. 'We wondered if pelagic (offshore) living promotes rapid postnatal maturation of muscle biochemistry', says Noren. In other words, might deep-diving ocean-going whales and dolphins develop large reserves of myoglobin and the ability to buffer muscle against acid earlier in in life than species that remain in shallow coastal waters? Noren and her colleagues measured the oxygen storage capacity and muscle biochemistry of spinner dolphin swim muscles and discovered that they matured no faster than the muscles of coastal species. They also publish their calculations suggesting that the muscles' slow development could place calves at risk of separation from their mothers during pursuits by commercial fishing fleets in Journal of Experimental Biology at http://jeb.biologists.com.

As it is almost impossible to collect muscle samples from spinner dolphins in the open ocean, Noren depended on Kristi West, from Hawaii Pacific University, USA - who set up a dolphin stranding program in Hawaii 11 years ago and attends all strandings on the island - to collect the essential samples. Over 7 years, West collected small portions of the swimming muscle from 17 spinner dolphins that her team had been unable to rescue - ranging in age from a foetus that died during birth to newborns, adolescents and fully grown males and females. She then shipped the samples to Santa Cruz, where Noren painstakingly analysed the muscles' myoglobin content and how much sodium hydroxide she had to add to 0.5g of minced muscle to raise the pH from 6 to 7 to measure the muscle's buffering capacity against anaerobic acid production. Plotting the animals' body lengths (which correlate well with their ages) against their muscle myoglobin content, Noren could see that the dolphins' abilities to carry oxygen continued increasing as the animals aged. The ability of the muscle to buffer against pH changes also increased gradually; however, it reached the capacity of the mature dolphins and plateaued at an age around 1.6-2 years, when the dolphin youngsters are weaned, which is similar to the age at which the diving apparatus of some coastal species reaches maturity.

So ocean-going spinner dolphin calves do not develop the physical characteristics that are essential to sustain deep dives any faster than shallow-diving coastal species, such as bottlenose dolphins. However, the youngest spinner dolphins already had higher concentrations of muscle myoglobin than coastal bottlenose dolphins at the same ages, and the adult spinner dolphins' myoglobin concentrations (6-7.1g of Myoglobin/100g of wet muscle mass) matched those that had been measured previously for other champion divers, including short-finned pilot whales and Gervais' beaked whales.

But what implications might the relatively slow development of their diving apparatus have for young spinner dolphins in the Eastern Tropical Pacific? Knowing that tuna purse-seine fisheries in this region specifically target dolphin pods - they pursue the animals to exhaustion before encircling them in enormous nets to capture the tuna shoals that reside beneath - Noren calculated that an immature calf that cannot keep up might be adrift of its mother by up to 15.4km by the end of a 100min pursuit. Noren says, 'The relatively underdeveloped muscle biochemistry of calves likely contributes to documented mother-calf separations for spinner dolphins chased by the tuna purse-seine fishery', and this could affect dolphin populations dramatically if our hunger for tuna continues to separate dolphin calves from their mothers.
-end-
IF REPORTING THIS STORY, PLEASE MENTION JOURNAL OF EXPERIMENTAL BIOLOGY AS THE SOURCE AND, IF REPORTING ONLINE, PLEASE CARRY A LINK TO: http://jeb.biologists.org/content/220/8/1490.abstract

REFERENCE: Noren, S. R. and West, K. (2017). Muscle biochemistry of a pelagic delphinid (Stenella longirostris longirostris): insight into fishery-induced separation of mothers and calves. J. Exp. Biol. 220, 1490-1496.
DOI: 10.1242/jeb.153668.

This article is posted on this site to give advance access to other authorised media who may wish to report on this story. Full attribution is required, and if reporting online a link to jeb.biologists.com is also required. The story posted here is COPYRIGHTED. Therefore advance permission is required before any and every reproduction of each article in full. PLEASE CONTACT permissions@biologists.com

The Company of Biologists

Related Dolphins Articles:

Exeter researchers help protect Peru's river dolphins
River dolphins and Amazonian manatees in Peru will benefit from new protection thanks to a plan developed with help from the University of Exeter.
New study defines the environment as an influencer of immune system responses in dolphins
Two populations of wild dolphins living off the coast of Florida and South Carolina are experiencing more chronically activated immune systems than dolphins living in controlled environments, raising concerns of researchers about overall ocean health, and the long-term health of bottlenose dolphins.
Immature spinner dolphin calf SCUBA tanks spell disaster in tuna fisheries
Dolphins that live in the deep ocean have well developed oxygen storage, but now it turns out that spinner dolphin calves do not develop their SCUBA capacity any faster than coastal species, despite their deep diving lifestyle.
The latest HKU study clarifies how many dolphins there are in Hong Kong waters
The latest study by researchers at the University of Hong Kong (HKU) delivered the first-ever comprehensive population assessment of the Chinese white dolphins that inhabit Hong Kong waters, and what they found differs from the common public belief.
Crocodiles and dolphins evolved similar skulls to catch the same prey: Study finds
A new study involving biologists from Monash University Australia has found that despite their very different ancestors, dolphins and crocodiles evolved similarly shaped skulls to feed on similar prey.
Cutting-edge cameras reveal the secret life of dolphins
A world-first study testing new underwater cameras on wild dolphins has given researchers the best view yet into their hidden marine world.
Dolphins following shrimp trawlers cluster in social groups
Bottlenose dolphins near Savannah, Georgia are split into social groups according to whether or not they forage behind commercial shrimp trawlers, according to a study published Feb.
Scientists studying dolphins find Bay of Bengal a realm of evolutionary change
Marine scientists have discovered that two species of dolphin in the waters off Bangladesh are genetically distinct from those in other regions of the Indian and western Pacific Oceans, a finding that supports a growing body of evidence that the Bay of Bengal harbors conditions that drive the evolution of new life forms, according to a new study by the American Museum of Natural History(AMNH), WCS (Wildlife Conservation Society), and the cE3c -- Centre for Ecology, Evolution and Environmental Changes (Universidade de Lisboa).
Researchers probing the beneficial secrets in dolphins' proteins
Why reinvent the wheel when nature has the answer? That's what researcher Michael Janech, Ph.D. of the Medical University of South Carolina, has found to be true, drawing from the field of biomimicry where researchers look to nature for creative solutions to human problems.
Former pesticide ingredient found in dolphins, birds and fish
A family of common industrial compounds called perfluoroalkyl substances, which are best known for making carpets stain resistant and cookware non-stick, has been under scrutiny for potentially causing health problems.

Related Dolphins Reading:

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Digital Manipulation
Technology has reshaped our lives in amazing ways. But at what cost? This hour, TED speakers reveal how what we see, read, believe — even how we vote — can be manipulated by the technology we use. Guests include journalist Carole Cadwalladr, consumer advocate Finn Myrstad, writer and marketing professor Scott Galloway, behavioral designer Nir Eyal, and computer graphics researcher Doug Roble.
Now Playing: Science for the People

#529 Do You Really Want to Find Out Who's Your Daddy?
At least some of you by now have probably spit into a tube and mailed it off to find out who your closest relatives are, where you might be from, and what terrible diseases might await you. But what exactly did you find out? And what did you give away? In this live panel at Awesome Con we bring in science writer Tina Saey to talk about all her DNA testing, and bioethicist Debra Mathews, to determine whether Tina should have done it at all. Related links: What FamilyTreeDNA sharing genetic data with police means for you Crime solvers embraced...