De grootste kennisbank van het HBO

Inspiratie op jouw vakgebied

Vrij toegankelijk

Terug naar zoekresultatenDeel deze publicatie

Performance of Oyster breed "Crassostrea gigas" in the Eastern Scheldt

the influence of a natural reef and the inundation time on the performance of oyster breed at Viane

Rechten: Alle rechten voorbehouden

Performance of Oyster breed "Crassostrea gigas" in the Eastern Scheldt

the influence of a natural reef and the inundation time on the performance of oyster breed at Viane

Rechten: Alle rechten voorbehouden

Samenvatting

The aim of this study and research is focussed on the performance of oyster reefs in the Eastern Scheldt. The oysters in a reef can be dead or alive and some show better health and growth than others, the parameters that plays a role in this are i.e. the inundation time and competition. Oysters can form three-dimensional reefs and habitat modification occurs while they are eco-engineering species. The most common oyster species in the Eastern Scheldt is the "Crassostrea gigas" and the intertidal areas of the Eastern Scheldt are threaten by the sand deficit problematic and the effects of climate change. Oyster reefs can be a self-sustainable, integrated, innovative and cost-effective solution.
The performance of individual oysters in a reef can be influenced by the inundation time and position of the oyster in the reef which is important for the competition between the oysters. The main questions of this research are: (1)What is the influence of the inundation time (vertical gradient) on the performance (health and growth) of the Pacific oyster "Crassostrea gigas"? (2) What is the influence of an existing natural reef of medium size(horizontal gradient) on the performance (health and growth) of the Pacific oyster "Crassostrea gigas"?
A field set up was placed in the Eastern Scheldt at Viane from 19 March until 6 May. Two transects were made: one through an oyster reef (for on and after the reef) and one reference 20 m sideways from the reef. 480 oysters were placed in gauze socks with 10 intervals of 20 cm and attached to 16 bamboo sticks with in each interval 3 oysters. The horizontal gradient (influence reef) and vertical gradient (influence inundation period) could be measured with this method. The inundation time was calculated with the height measurements of the bamboo sticks and the water level data from Rijkswaterstaat. To measure the performance the shell characteristics (shell length, width and thickness), mortality rate and the condition indices (dry weight and ash free dry weight) were measured before and after the field period.
The average results of the inundation time showed that there was no significant difference for the shell characteristics and mortality rate between the different inundation times, however it could be indicated that there was a upper (80%) and lower limit (42%) and an optimum (42-74%). In general the condition indexes increase with the inundation time and the reference transect shows a better health condition than the reef transect, but there was no significant difference between the results.
The average results of the influence of the reef showed that there was no significant difference for the shell thickness and mortality rate. The condition indices however showed significant difference between the oysters for the reef and in the reference compared with the oyster on and after the reef.
Based on all results it can be concluded that the oyster performance is most affected by the inundation time; how greater the inundation time the better the health and growth. However it seems that there's a upper limit at 80% inundation time and an optimum around 60%. According to all results it seems that the oysters that are not influence by the oyster reef (in front of the reef and reference) shows better health and growth then the oysters that are influence by the reef (on and behind the reef). The restoration of existing oyster reefs can better occur on the front of the reef instead of on or after the
Final thesis: Oyster performance in the Eastern Scheldt
vi
reef. Adjacent of the reef new small artificial reefs/patches can congregate with the existing reef to enlarge the reef area and its effect.
The reliability of these results are moderate, because of the field period and circumstances. The weather was bad, the water was 3o C and storm events occurred several times, which had broken off bamboo sticks or make "them disappear". Furthermore, the variety in results between individual oysters was great and there weren't always enough results for a good statistical analysis (at least 10n).

Toon meer
OrganisatieHZ University of Applied Sciences
OpleidingWatermanagement/ Aquatische Ecotechnologie
AfdelingDelta Academy
PartnersRAAK-project Building with Nature group, Delta Academy, Vlissingen
Datum2013-08-29
TypeBachelorscriptie
TaalNederlands

Op de HBO Kennisbank vind je publicaties van 26 hogescholen

De grootste kennisbank van het HBO

Inspiratie op jouw vakgebied

Vrij toegankelijk