Archive for the ‘Marine Science’ Category

Who are you calling a shrimp?

Wednesday, January 21st, 2015

Life in the ocean can be tough – especially when you’re a shrimp. Not only are you tiny and tasty, but new research shows that competition between shrimp is often violent and brutal.

The Indo-Pacific and Red Sea host several cleaner shrimp that are known for their symbiotic relationship with fish. In return for a meal, the shrimp crawl over the fish removing dead skin and parasites. While the shrimp maintain a cordial relationship with their clients, they can be openly hostile towards members of their own species.

Cleaner shrimp usually live in monogamous pairs, but the battle to get down to 2 individuals can be quite fierce. Researchers recently tested the shrimp’s competitive nature and found that when more than 2 shrimp were in a tank, they would attack and kill until only a pair remained.

Shrimp, like most crustaceans, are at their most vulnerable right after they molt. The savvy competitor knows that this is the best time to strike the fatal blow to their opponent. It should come as no surprise then, that researchers found that when shrimp were kept in groups they would delay the molting process as long as possible. Whoever shed first was usually the first to go. However, once a harmonious pair was established, they would return to routine molting.

The most likely reason for this behavior is played out across the animal kingdom – competition for scarce resources. Food is a limiting factor in the ocean, and shrimp want to make sure that they have guaranteed access to it. This will also result in an increase in body size, and a corresponding increase in the number of eggs laid. Regardless of motivation, it is clearly a “shrimp eat shrimp” ocean out there.

Will JAWS fears become a thing of the past?

Wednesday, January 14th, 2015

While sharks occasionally take nips at our sea turtle friends, we don’t hold it against them. The oceans are big places, prey maybe hard to come by and as oceanic predators they’re only obeying their animal instincts. They also occupy an important role as apex predators, and can serve as an indication of overall ocean health.

That is why a recent study published in Biology Letters causes pause for concern. Researchers from UC Davis and Stanford University have been conducting population estimates of great whites in the northeast Pacific. Their preliminary results surprised even themselves, “It’s lower than we expected, and also substantially smaller than populations of other large marine predators, such as killer whales and polar bears,” says the study’s lead author Taylor Chapple.

Using a seal-shaped decoy, researchers were able to photo ID individual species by their trademark dorsal fins. The jagged edges along the margins are unique, like fingerprints. Using this technique, researchers estimate that the region has 219 adult and sub-adult great whites. A sub adult is classified as having reached 8-9 feet in length and having shifted their diet from primarily fish to primarily marine mammals. An adult is a shark that has reached sexual maturity, which typically happens at 13 feet (in males) or 15 feet (in females).

The North American West Coast is one of three known white shark populations, the others being Australia/New Zealand and South Africa, and it is the location with the best population estimates. While numbers are lower than expected, further studies are needed to determine whether this is a population that is healthy or on the verge of collapse. Large pelagic fish species like tuna and billfish are in decline due to overfishing, and is conceivable that the great whites are suffering a similar fate.

Turtle Toxicology Troubles

Wednesday, January 7th, 2015

While sea turtles appear to be having another banner nesting season along the North Carolina coastline (109 nests at Topsail so far), some new reports seem to indicate a cause for concern below the sand. A recent study from Alava et al. published in Environmental Toxicology and Chemistry compared the amount of persistent organic pollutants (or POPs) in the eggs of loggerhead sea turtle nests at various locations – and the conclusions don’t bode well for North Carolina.

Researchers sampling nests from Florida’s Gulf Coast, Florida’s Atlantic Coast, and North Carolina found that eggs from North Carolina contained higher levels of the harmful POPs. These pollutants (which include PCBs, DDT-related compounds, and organochlorine pesticides) can result in lower mass to length ratios in hatchlings, affect predator avoidance, and negatively impact development in early life stages.

This difference in POP concentration in the eggs has been linked to the different feeding strategies of the loggerheads from these different populations. Loggerheads along Florida’s west coast primarily feed in the Gulf of Mexico and the Caribbean, while North Carolina’s loggerheads feed along the Atlantic coast from New Jersey to Georgia. The coastline from Georgia to New Jersey is more heavily populated and prey from these waters are more contaminated with POPs than those in the other locations.

This is further evidence that sea turtle conservation isn’t simply a coastal issue. It involves land management decisions, pesticide and fertilizer restrictions, plastic usage, and myriad other concerns that can originate in the heartland of our country and filter out to our waterways. Please let us know how you are doing your part in your community!

Determining the real cost

Wednesday, December 24th, 2014

Most of us have slipped. We’re running out of the drug store, picking up  groceries, or ordering  take out – and then we’re faced with it. We realize our trusty reusable bags are at home and we’re left with the plastic bag. The plastic bag may look benign. It goes as far as camouflaging its true nature by being covered with smiley faces or friendly greetings. Despite this façade, it’s time that we start to view the plastic bag for what it really is – an insidious, life threatening weapon.

As more disposable plastic items appear on the consumer market, the threat to our ecosystem and its habitats also increases. Several years ago, India faced a spate of cow deaths. These revered animals roam throughout the cities and are treated as deities. Necropsies later revealed that the cows had ingested large quantities of plastic bags which had blocked (or impacted) their digestive tracts.

Plastic impaction is not isolated to terrestrial animals, as the volunteers at the Karen Beasley Sea Turtle Hospital well know. Little bits of plastic have found their way into the sea turtle diet, providing no nutritional value and posing devastating consequences. A recent study published in Marine Biology looked at the digestive contents of loggerhead sea turtles in the Gulf of Mexico and found that “anthropogenic debris was present in the digestive tract contents of 51.2% of the loggerheads”. Pieces of disposable plastic bags made up the primary component.

Plastics are pervasive because they are cheap and easy. Recent cleanups of a half mile stretch of beach in Logartillo, Costa Rica yielded 14,000 plastic marine debris items, which included lots of monofilament fishing line. Their inability to decompose like other products (plastics photodegrade, instead of biodegrade), makes it a problem that will be around for generations to come. Their cheapness doesn’t factor in the environmental costs of a dead sea turtle impacted with nurdles or entangled in abandoned monofilament nets. Next time your grocer starts putting your items in a plastic bag, please consider all the additional costs.

Olive ridley turtle

Wednesday, November 26th, 2014

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Common name: Olive ridley turtle

Scientific name: Lepidochelys olivacea

Distribution: Tropical waters worldwide

Nests on: Tropical beaches worldwide

Beach type: Tropical mainland shores and barrier islands, often near river mouths.Throughout mainland; also Andaman and Nicobar and to a lesser extent, Lakshadweep Islands.

Weight (adult): Olive ridley turtle50 kg

Carapace length: 60 – 70 cm

Carapace shape: Short and wide, carapace smooth but elevated, tectiform (tent-shaped).

Colouration: Mid to dark olive green

Costal scutes: 5 – 9 pairs asymmetrical

Head shape: Large, triangular

Prefrontal scales: 2 pairs

Limbs: Two claws on each flipper

Plastron: Pore near rear margin of infra marginals; creamy yellow

Other features: Vertebrals (centrals) narrow, so that first costal contacts nuchal scute.

Time of nesting: Night

Clutches per season: 1 – 3

Clutch size: 100 – 120

Egg size: ~ 4 cm in diameter

Re-nesting interval: 20 – 28 days

Re-migration interval: 1 – 2 years

Track: 70 – 80 cm wide, light, with asymmetrical, oblique marks made by forelimbs, tail drag mark lacking or inconspicuous.

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