Despite broad “dolphin safe” practices, fishing activities have continued to restrict the growth of at least one Pacific Ocean dolphin population, a new from a researcher at Scripps Institution of Oceanography at UC San Diego concluded.
The new study, published in the October issue of Marine Ecology Progress Series, reveals that negative impacts from fishing activities remain. Instead of reducing numbers through direct mortalities, the study by Katie Cramer of Scripps Institution of Oceanography and Wayne Perryman and Tim Gerrodette of the National Oceanic and Atmospheric Administration’s (NOAA’s) Southwest Fisheries Science Center shows that fishing activities have disrupted the reproductive output of the northeastern pantropical spotted dolphin.
The Pantropical Spotted Dolphin, Stenella attenuata, is a species of dolphin found in all the world’s temperate and tropical oceans. The species is under threat due to the killing of millions of individuals in tuna purse seines. The 1980s saw the rise of “dolphin-friendly” tuna capture methods in order to save millions of the species in the eastern Pacific Ocean.
Dolphins in the Eastern Pacific were expected to increase in abundance after successful regulations and agreements were enacted to reduce dolphin deaths as a result of fishing “by-catch,” cases in which animals are caught unintentionally along with intended targets
In the eastern Pacific, the Dolphin is often found swimming with Yellow fin Tuna (hence the problem with dolphin deaths caused by tuna fishing. However they do not feed on that fish. In fact the two species have a similar diet of small surface feeding fish. In other areas the species may also feed on squid and crustaceans.
Birth length is 80-90 cm. Adults are about 2.5 m long and weigh 120 kg. Sexual maturity is reached at 10 years in females and 12 years in males. Lifespan is approximately 40 years.
The Pantropical Spotted Dolphin is found across all tropical and sub-tropical oceans and seas between 40° N and 40° S. The total world population is in excess of three million — the second most abundant cetacean after the Bottle nose Dolphin of which two million are found in the eastern Pacific. However, this represents a decrease from at least 7 million since the 1950s.
Centers of highest population density are the shallow warmest waters (water temperature in excess of 25 °C). The Pantropical Spotted Dolphin is very active and is prone to making large splashy leaps from the sea. It is a common breacher and will often clear the water for a second or more. Bow-riding and other play with boats is common much to the delight of the humans watching.
Excerpts from Dolphin Population Stunted By Fishing Activities
– Staff Seed Daily December 2, 2008
Image courtesy of: Dolphins in a purse-seine net. Image courtesy of NOAA Fisheries, Southwest Fisheries Science Center, Protected Resources Division. -Staff Writers La Jolla CA (SPX) December 2, 2008
Image courtesy of MarineResearch: marineresearch.ca/spinnerPIFSC