Enhancing hatchery production efficiency for commercial offshore cultivation of giant kelp (macrocystis pyrifera) in Luderitz, Namibia

Abstract

<title>Abstract</title> <italic>Macrocystis pyrifera</italic> is a potential candidate for aquaculture because it grows rapidly, forms extensive underwater forests, and yields substantial biomass; and was the focus of this study. This study assessed sporophyte production by gametophytes of <italic>M. pyrifera</italic> obtained from three populations: California (CAL), South Africa (CAT), and the Falkland Islands (FL) in relation to environmental parameters. Factors examined included temperature (7.5, 10 - control, 12.5°C), irradiance (22.5, 30 - control, 37.5 µmol m⁻² s⁻¹), and gametophyte stocking densities (0.085, 0.114 - control, 0.142 mg cm⁻²). The data collected were the time required for sporophyte generation at weekly intervals and the quantities of sporophytes produced per cm². results indicated that a temperature of 12.5°C accelerated sporophyte production across all populations, with outputs of 126.03 (± 101.44) in CAL, 694.44 (± 244.46) in CAT and 1265.42 (± 448.30) in FL. At 7.5°C, no viable sporophyte production was observed for either CAL or CAT, whereas for FL, an increase in sporophyte quantities was observed (2142.49 (± 736.44)). In FL, reduced irradiance (22.5 µmol·m⁻².s⁻¹) resulted in increased sporophytes outputs (1705.25 (± 657.28)), while the control irradiance (30 µmol·m⁻². s⁻¹) was optimal for CAL 259.26 (± 203.16) and CAT 1970.16 (± 888.01). Gametophyte stocking density yielded the highest sporophyte outputs in CAT (1898.15 (± 534.67)) and FL (749.42 (± 359.09)) at the control treatment, while no differences were recorded for CAL between all density treatments. This study revealed that the optimization of sporophyte production through parameter manipulation enhances efficiency, and future research can explore increased lab temperature and its impact on sea recruitment rates.