1. An aquatic organism growth promotor, comprising, as an effective ingredient, a low molecular weight lignin having a molecular weight peak in a molecular weight range of 4,000 to 9,500 and/or a high molecular weight lignin having a molecular weight peak in a molecular weight range of 10,000 to 40,000, wherein said molecular weight peak is measured at a wavelength of 254 nm by GPC molecular weight analysis using an UV detector.
2. The aquatic organism growth promotor according to claim 1, wherein said low molecular weight lignin and/or said high molecular weight lignin are/is derived from an alkaline hot-water extract from bagasse.
3. The aquatic organism growth promotor according to claim 1 or 2, which promotes the ecdysis of a crustacean.
4. An aquatic organism growth promotion feedstuff, comprising said aquatic organism growth promotor.
5. The aquatic organism growth promotion feedstuff according to claim 4, comprising said low molecular weight lignin and/or said high molecular weight lignin, wherein the lignin(s) content as a polyphenol amount is 0.007 wt% or more in terms of catechin.
6. A method of promoting aquatic organism growth, comprising administering said aquatic organism growth promotor to an aquatic organism.
7. A method of promoting aquatic organism growth, comprising feeding said aquatic organism growth promotion feedstuff to an aquatic organism.
8. The method of promoting aquatic organism growth according to claim 6 or 7, wherein said aquatic organism is a crustacean.