Full description
In the Derwent Estuary (south eastern Tasmania, Australia), the introduced northern Pacific seastar Asterias amurensis is highly abundant and fecund when associated with anthropogenic structures (wharves and marinas). Based on modelled predictions of fertilisation success, seastars at wharf 'hotspots', whilst representing <10% of the total population in the Derwent Estuary, and concentrated in <0.1% of the total area, contribute up to >80% of total larval production in the estuary.Reproductive potential of populations at wharf and control sites was quantified (in terms of individual capacity and spatial characteristics of the population. A large scale survey was undertaken in the Derwent estuary (to 27m) to determine spatial distribution of the species. Zygote production (i.e. number of fertilised eggs) was used as a measure of reproductive output and was simulated using empirical estimates of spatial and reproductive parameters of the adult seastars in a spatially explicit model of fertilization (developed by A. Morris and C. Johnson).
Lineage
Maintenance and Update Frequency: notPlanned
Statement: 1. Reproductive potential of Asterias amurensis in SE Tasmania
Sites
Derwent River estuary: 3 adjacent to anthropogenic structures (Derwent Sailing Squadron marina: 4m, Princess wharf:8-14m, Bellerieve Yacht Club marina:6m); and 3 control sites (Trywork Point:6-10m, 2nd Bluff: 6-10m, Sandy Bay:6m).
Reproductive capacity
Thirty adult A.amurensis (ray length >55mm) were collected from each site every 2 weeks prior to spawning until after the peak spawning period (July-Oct, 1999). Water temperature was recorded (at seafloor) at each site for each sampling occasion. In the laboratory, seastars were dissected and gonads and total body weight (wet) were measured. Individuals were sexed and ray length measured.
Small scale spatial distribution
Belt transects (2x10m at wharf sites, 2x30m at control sites) were used to estimate the density and dispersion of individuals concurrent with time at which reproductive capacity was estimated. A 60m baseline was established parallel to wharf or shore, 6 belt transects were set perpendicular to the this at random positions within each 10m interval (with interception point also random). Seastar abundance was recorded every 2m.
Availability of mussels as a food source
Mussels (Mytilus edulis planulatus) are a preferred food source of A.amurensis, and their availability was therefore quantified at wharf sites (and were absent at control sites). The abundance of seastars, abundance of live mussels, and abundance of seastars feeding on mussels was assessed in 1x1m quadrats. At each wharf site, 10m transects perpendicular to the wharf were laid at 5m intervals with quadrats at 0, 3, 5, 7 and 10m's along the line.
2. Large scale spatial distribution of A. amurensis in the Derwent River estuary, SE Tasmania
A remote underwater video camera mounted on a sled and towed behind a vessel was used to survey A. amurensis in the Derwent River estuary. Three paired video transects were deployed perpendicular to the shore in the 4 designated zones (northern, Ralphs Bay, southeastern and southwestern zones) in Sept/Oct 1999. Transects were divided into ranges (3-5, 6-10, 11-15, 16-20 and 20+ metres). Tow duration was 20 minutes, with depth recorded every minute. Field of view was 1x1m. Tow speed was calculated from the footage using a stop watch, and the distance covered estimated from the average speed over the benthos.
Benthic video footage currently on VHS tapes, with plans to digitise in the future - see Scott Ling.
Notes
CreditRoss, Jeff, Dr
Credit
Mundy, Craig, Dr
Mundy, Craig, Dr
Credit
Morris, Alice
Morris, Alice
Purpose
To investigate whether fertility hotspots exist across the seastars stronghold in the Derwent Estuary and if such populations can be targets for pest management strategies.
To investigate whether fertility hotspots exist across the seastars stronghold in the Derwent Estuary and if such populations can be targets for pest management strategies.
Created: 09 09 2008
Data time period: 07 1999 to 31 10 2000
text: westlimit=147.5; southlimit=-43.5; eastlimit=148.0; northlimit=-42.5
text: uplimit=27; downlimit=3
Subjects
25 154001 |
Agricultural and Veterinary Sciences |
ANIMALS/INVERTEBRATES |
AQUATIC ECOSYSTEMS |
Aquatic Ecosystem Studies and Stock Assessment |
Asterias amurensis |
BIOLOGICAL CLASSIFICATION |
Biological Sciences |
BIOSPHERE |
EARTH SCIENCE |
Echinoderms |
Ecology |
Fisheries Sciences |
Gonad Index |
Gonad mass |
Marine and Estuarine Ecology (Incl. Marine Ichthyology) |
Mussel density |
Reef Habitat |
Seastar density |
Seastar mass |
biota |
User Contributed Tags
Login to tag this record with meaningful keywords to make it easier to discover
Identifiers
- global : 4634fa40-7e0b-11dd-a21f-00188b4c0af8
