Hyperpigmentation in North Sea dab Limanda limanda. I. Spatial and temporal patterns and host effects

Area of Science:

• Marine biology
• Fish pathology
• Environmental toxicology

Background:

• Hyperpigmentation is a pigment anomaly observed in common dab (Limanda limanda) and other North Sea flatfish.
• The condition presents as green to black spots on the upper body side and white spots on the lower side.
• Previous studies noted hyperpigmentation in specific North Sea regions.

Purpose of the Study:

• To analyze the spatial and temporal patterns of hyperpigmentation in North Sea flatfish.
• To investigate the relationship between hyperpigmentation prevalence, intensity, and fish-specific factors.
• To discuss potential causes and contributing factors to the observed hyperpigmentation trends.

Main Methods:

• Analysis of fish disease monitoring data from Germany, the UK (England and Scotland).
• Statistical analysis of hyperpigmentation prevalence and intensity in relation to fish size, age, growth, and condition factor.
• Examination of spatial and temporal trends in hyperpigmentation across North Sea areas.

Main Results:

• A pronounced spatial pattern of hyperpigmentation was detected in the North Sea.
• Prevalence increased significantly in most studied areas over two decades, from 5% to over 40% in hotspots.
• Hyperpigmentation prevalence and intensity correlate positively with fish size and age, and negatively with condition factor.

Conclusions:

• Hyperpigmentation in common dab shows increasing prevalence and intensity in the North Sea, particularly with age.
• The condition's spatial and temporal patterns suggest environmental influences, potentially linked to factors like UV-B radiation, nutrition, or temperature.
• Further research is needed to elucidate the exact causes and the interplay of host-specific factors.