The specific growth rate (SGRd) of juvenile Fenneropenaeus chinensis shrimp was measured over 35 days under different light intensities: 0, 50, 300, 1300 and 5500 lx. The SGRd of the shrimp under 5500 lx was only 29.4%, 27.1%, 21.1% and 19.7% of those under 0, 1300, 50 and 300lx, respectively ( P<0.05). The maximal and minimal feed intake (FId) of shrimp occurred under 300 and 5500lx, respectively (difference 9.3%). The lowest food conversion efficiency (FCEd) occurred in the 5500 lx group (30.2%, 26.3%, 21.3% and 21.1% of those under 0 lx, 1300lx, 50lx and 300lx, respectively). FCEd values between 5500 lx and other groups were significantly different (P<0.05). The shrimp under 5500 lx gained a lower FI as well as a lowest FCE and therefore exhibited a lower SGR. The results revealed that light intensity affected the growth of the shrimp mainly by influencing FCE, or energy allocation to growth. Therefore, the shrimp may grow better in organically rich earthen ponds that have lower light intensity.

The specific growth rate (SGR) over 45 days of Fenneropenaeus chinensis shrimp with initial body weight of 1.979F0.036 g under different light color was as follows: natural>green>yellow>blue light. The SGR of shrimp under blue light was only 73.0% and 85.8% of those under natural light and green light, respectively. The maximal and minimal feed intake (FI) of the animal occurred under blue light and yellow light (difference 16.6%), respectively. The lowest food conversion efficiency (FCE) occurred in the blue light group (64.5% and 75.8% of that under natural and green light, respectively). FCE values between blue and natural light groups were significantly different (P<0.05). F. chinensis was relatively sensitive to blue light, under which the animal was active in feeding behavior, and gained a higher FI as well as a lower FCE, and therefore, a lower SGR.Shrimp may grow faster in the organically rich earthen ponds than in organically poor waters because there is less blue light spectrum in earthen ponds.

Allelopathic effects of fresh tissue and dry powder of a nonsexual and a sexual strain of the macroalga Ulva pertusa on the growth of the microalgae Heterosigma akashiwo and Alexandium tamarense were evaluated using long-term coexistence culture systems in which several concentrations of macroalga fresh tissue and dry powder were used. The effects of macroalga culture medium filtrate on the two HAB algae were also investigated. Moreover, isolation co-culture systems were built to confirm the existence of allelochemicals and preclude the growth inhibition by direct contact. Short-term algicidal effect assays of macroalgae on H. akashiwo were carried out to measure the rate of algal cell lysis. The results of the coexistence assays showed that the growth of H. akashiwo and A. tamarense was strongly inhibited by fresh tissue and by dry powder of both strains of U. pertusa. The allelochemicals were lethal to H. akashiwo at relatively higher concentrations. The macroalga culture medium filtrate exhibited no apparent growth inhibitory effect on the two HAB algae under initial or semicontinuous filtrate addition, which suggested that continuous release of small quantities of rapidly degradable allelochemicals from the fresh tissue of both strains of U. pertusa was essential to effectively inhibit the growth of H. akashiwo and A. tamarense.