Re: Why do people capture dolphins?

Humans have had a long-standing relationship with the smaller cetaceans 
(dolphins and porpoises) often based on their curiosity and willingness 
to approach and play around human boats.  Documentation of their habit of 
bow-riding relatively fast or larger ships goes back to at least greek 
times, along with stories of them helping stranded or drowning men (which 
has some basis in fact).  However, humans have also historically hunted 
them for food (for an abstract of the history of hunting bottlenosed and 
river dolphins in latin america, see Romero, A.; A. I. Agudo & S.M. 
Green. 1997. Exploitation of Cetaceans in Venezuela. Reports of the 
International Whaling Commission 47:735-746 - the abstract can be found 
on this website:
 http://www.clt.astate.edu/aromero/new_page_158.htm

Japan has also had a long history of hunting dolphins and whales for 
food, and there is a summary of some of this historical information on 
this web page:
 http://www.kanazawa-med.ac.jp/~hum-sci/iruka-e.htm

While most nations have signed a moratorium on whaling, several nations, 
including Norway and Japan, continue to hunt both small and large 
cetaceans, ostensibly for "research" purposes, but with the bodies used 
for consumer products such as pet food after the research is completed.  

For those nations who adhere to the moratorium or have more stringent 
national restrictions (such as the US's Marine Mammal Protection Act of 
1972 - see the National Oceanographic and Atmospheric Administration's 
web page for a full description of the MMPA)
 http://www.nmfs.noaa.gov/prot_res/laws/MMPA/MMPA.html

dolphin capture is highly restricted - even capture for zoos, parks and 
aquaria is usually limited to maintaining animals that have been rescued 
(from strandings, injuries, etc) rather than sought out for display 
purposes. Actions by parks and aquaria in obtaining wild dolphins from 
countries which do not have such have yielded severe criticism, such as 
the recent attempt to gather a number of dolphins for Mexican aquaria by 
paying fishermen in the Solomon Islands to catch them.  A mexican 
business consortium offered local fisherman ~$400 for each dolphin they 
catch, when though each is sold for about $225,000 to the dolphinaria.

Here is a fact sheet from the American Cetacean Society on the event
 http://www.acsonline.org/issues/captivity-swim-with/SolomonIsl-dolphins.html