This fish processing by-product is high in Nitrogen, and contains phosphorous and potassium, all 3 of which are elements that are essential to the growth and health of plants. A little goes a long way (1 to 2 tablespoons to 1 gallon of water), and the product can last indefinitely if stored properly (a cool place, out of direct sun). You can use this once a month during your plants' growing season, or cut the dosage in half, and use with each watering.
For more details about the scientific process, read this excerpt below from pennington.com
Some quick release synthetic fertilizers offer immediate nutrients in the garden because they are processed to be readily available for plants to absorb. All-natural fish fertilizers are processed differently in the soil, because they contain nutrients that must first be digested by organisms, such as bacteria, earthworms and fungi, before they are available for plant roots to use. All of this microbial activity enhances the strength and vigor of plants by increasing the amount of organic matter in the soil. Fungi and bacteria break down nutrients to make them available to plant roots, and then loosen the dirt as they travel, reproduce, process nutrients and decay, leaving soil aerated with improved levels of organic matter. Plant roots grow faster and stronger in this light, airy soil that is teeming with life.
As fish fertilizer improves soil health, it also increases soil fertility by providing the primary nutrients necessary for plants to thrive. Fish fertilizers offer a source of burn-free nitrogen, along with the other primary nutrients of phosphorus and potassium. Unlike synthetic options, they may also provide secondary nutrients, such as calcium, which is found in Alaska dry fertilizers. Plants that receive a balance of primary and secondary nutrients experience strong and steady plant growth, leading to vigorous plants that can better withstand disease and pest issues.