I believe the question is referring to multi-trophic aquculture (not agriculture) as this is more well known.
The term trophic refers to food/nutritution and in biological systems "trophic levels" are usually associated with different stages in a food chain.
Integrated multi-trophic aquaculture (IMTA) therefore, defines a form of aquaculture (an artificial human created process) that has multiple stages of the food chain optimised as they might be in nature. What this usually means is that the waste products from one stage feed into another stage as inputs, in the way that foodwebs work in reality. This increases efficiency.
For example, fish and shrimp might be mixed with seaweed and shellfish which each fill a niche in the food web to produce a more stable artificial ecosystem.
