Macrocystis Biomass, Quality, and Harvesting Effects in Relation to the Herring Spawn-On-Kelp Fishery in Alaska
van Tamelen P and Woodby D. 2001. Macrocystis Biomass, Quality, and Harvesting Effects in Relation to the Herring Spawn-On-Kelp Fishery in Alaska. Alaska Fishery Research Bulletin. 8(2):118-131
Giant kelp Macrocystis spp. is harvested for use in herring spawn-on-kelp, also called roe-on-kelp, fisheries, but information on the biology and ecology of kelp is limited for Southeast Alaska. A successful management plan must evaluate both the amount of kelp available for harvest and the recovery rates of kelp from harvest. In this study, estimating the amount of kelp available consisted of first estimating the total abundance of kelp in a survey area and second estimating the biomass of available and desirable kelp. The total biomass was estimated by surveying the surface area of kelp beds in selected regions on the west coast of Prince of Wales Island. Randomly selected “index beds” were surveyed to determine kelp density, and samples were measured and weighed to estimate the average weight of kelp fronds. About 2.04 x 105 t of kelp were identified in the survey. The harvest of kelp for spawn on kelp is highly selective. We found that blades at least 14 cm wide and fronds with a high proportion of desirable blades were selected. The proportion of blades and fronds meeting these selection criteria were determined for the index beds, and the biomass of desirable kelp was estimated to be about 14% of the total kelp biomass in April. The growth in kelp canopy was rapid from March to April, with April canopies about 82% larger than March canopies. Even if kelp harvests increase 10 times over present levels, the harvest will represent only about 4.5% of the total estimated amount of kelp. Experimentally harvesting kelp canopies in March, April, or at both times had few significant effects. Kelp beds that were experimentally harvested at both times or only in April had shorter fronds and possibly fewer large fronds and fronds per plant. This experiment was monitored only one month after the last harvest, so there may not have been sufficient time for the cut kelp to recover.
- Type
- Journal Article
- Authors
- van Tamelen, PG; Woodby, D
- Units
- GLBA
- Keywords
- Alexander Archipelago, Coastal/Marine Systems, Fishery Management, Gulf Of Alaska, herrring roe fishery, Kelp, marine fisheries, Prince of Wales Island