Why would it be expected that a swordfish would exhibit higher methyl mercury levels than a tilapia? (site 2)

Answer is explained below;

Explanation:

Mercury is a liquid metal that is released into the environment by both natural processes such as volcanic activity, weathering of rocks, etc and human activities such as waste materials from factories. The mercury that reaches the ocean and other water sources is converted into methylmercury by bacteria. Methylmercury is a neurotoxin that interferes with the nervous system and is easily absorbed by the human body.

The methylmercury is taken up by planktons. Small fishes consume large quantities of plankton. Tilapia is a small, short-lived freshwater fish. The methylmercury level in tilapia is lower than that of other fish. When large, long-living predatory fishes such as tuna, shark, king mackerel, swordfish, etc consume many smaller fish with low mercury levels, this causes accumulation of methylmercury at extremely high levels in their tissues over time i.e., the amount of mercury in such bigger fish biomagnifies.  

So large, long-lived predators like swordfish and shark often have the highest methyl mercury levels than a small, short-lived tilapia.

that would be called plucking : )

explanation:

''plucking, also referred to as quarrying, is a glacial phenomenon that is responsible for the erosion and transportation of individual pieces of bedrock, especially large "joint blocks". as a glacier moves down a valley, friction causes the basal ice of the glacier to melt and infiltrate joints (cracks) in the bedrock."