There is no current consensus regarding which of the two main hypotheses (grazing or micronutrients) controls production in these equatorial waters. It is likely that trace metal limitations select for smaller-celled organisms, which thereby increases the grazing pressure of protists. While the Equatorial Pacific maintains HNLC characteristics, productivity can be high at times. Productivity leads to an abundance of seabirds such as storm petrels near the convergence of subtropical water and the equatorial "cold tongue." The Equatorial Pacific contains the world's largest yellowfin tuna fisheries and is home to the spotted dolphin.