Assessing structure and seasonal variations of a temperate shallow water fish assemblage through Snorkel Visual Census

TY - JOUR

T1 - Assessing structure and seasonal variations of a temperate shallow water fish assemblage through Snorkel Visual Census

AU - Holm-Hansen, Tore Hejl

AU - Carl, Henrik

AU - Gravlund, Peter

AU - Krag, Marcus Anders

AU - Moller, Peter Rask

PY - 2019/12

Y1 - 2019/12

N2 - The shallow, brackish waters of the western Baltic Sea play a significant role in the life cycle of several commercial fishes, both as nursery and foraging areas. The fish assemblages of the inner 100 m is, however, surprisingly poorly studied, due to lack of effective methods for monitoring all fish species. In the present study, we applied Snorkel Visual Census (SVC) as a tool in monitoring shallow water (< 5 m) fish assemblages at two brackish shallow water localities in the Sound, Denmark. The survey was conducted through 15 consecutive months (June 2013-August 2014), during which a total of 36 species were registered. Assemblages were numerically dominated by Gobiusculus flavescens (Fabricius, 1779) (50%) and Gasterosteus aculeatus Linnaeus, 1758 (45%). Analysis of temporal, spatial and environmental factors revealed that temperature was the single most powerful factor affecting species richness, and had a significant effect on fish abundance, which in addition showed significant seasonal variations. Species richness showed a quadratic correlation to temperature with an optimum of similar to 14 degrees C. Abundances of individual species were affected by temperature and salinity, and showed both seasonal, spatial and diel variations. The negative effect of high temperatures on species richness was not seen at night, indicating that marine species utilize these areas as nocturnal feeding grounds or to avoid larger predators. Our findings show that SVC is effective in monitoring diversity of shallow, temperate water fish communities providing both qualitative and quantitative information on seasonal variations in species abundance and assemblage structure.

AB - The shallow, brackish waters of the western Baltic Sea play a significant role in the life cycle of several commercial fishes, both as nursery and foraging areas. The fish assemblages of the inner 100 m is, however, surprisingly poorly studied, due to lack of effective methods for monitoring all fish species. In the present study, we applied Snorkel Visual Census (SVC) as a tool in monitoring shallow water (< 5 m) fish assemblages at two brackish shallow water localities in the Sound, Denmark. The survey was conducted through 15 consecutive months (June 2013-August 2014), during which a total of 36 species were registered. Assemblages were numerically dominated by Gobiusculus flavescens (Fabricius, 1779) (50%) and Gasterosteus aculeatus Linnaeus, 1758 (45%). Analysis of temporal, spatial and environmental factors revealed that temperature was the single most powerful factor affecting species richness, and had a significant effect on fish abundance, which in addition showed significant seasonal variations. Species richness showed a quadratic correlation to temperature with an optimum of similar to 14 degrees C. Abundances of individual species were affected by temperature and salinity, and showed both seasonal, spatial and diel variations. The negative effect of high temperatures on species richness was not seen at night, indicating that marine species utilize these areas as nocturnal feeding grounds or to avoid larger predators. Our findings show that SVC is effective in monitoring diversity of shallow, temperate water fish communities providing both qualitative and quantitative information on seasonal variations in species abundance and assemblage structure.

KW - ABUNDANCE

KW - COMMUNITIES

KW - Coastal fishes

KW - DIEL

KW - DIVERSITY

KW - ECOSYSTEM

KW - Gobiusculus flavescens

KW - HABITAT

KW - MARINE RESERVE

KW - REEF

KW - ROCKY

KW - Seasonal variation

KW - Snorkel Visual Census

KW - THERMAL PHYSIOLOGY

UR - http://www.scopus.com/inward/record.url?scp=85078903394&partnerID=8YFLogxK

U2 - 10.26028/cybium/2019-434-004

DO - 10.26028/cybium/2019-434-004

M3 - Journal article

SN - 0399-0974

VL - 43

SP - 341

EP - 350

JO - Cybium

JF - Cybium

IS - 4

ER -