Tub gurnard (Chelidonichthys lucerna)
Also known as: sapphirine gurnard, searobin, tub, tubfish, tube-fish, tubfish, yellow gurnard, yellow-gurnard
Morphology & Biology
The tub gurnard is a medium-sized bottom-dwelling fish, with a reddish shimmering body, an armoured head and finger-like belly rays which they can use to “run” over the sea floor. They have an elongated reddish-brown body, with blue spots on top and a whitish to pink belly. Their large triangular head is armoured with ridges, and the front gill covers are spiked; making them part of the scorpionfish. The tub gurnard has a terminal mouth (pointing straight forward) and prominent lips. When swimming through open water they use their large, wing-like pectoral fins. There are three isolated rays on the pectoral fin, which have a similar function to legs. These are studded with tactile organs and taste cells and support the fish and also serve to locate food in the soft bottom.
Tub gurnards hunt other bottom-dwelling fish, crustaceans and molluscs. Unlike other gurnards, however, they also hunt in open water and on the surface.
The average tub gurnard reaches a size of 30-40cm and a weight of 1kg. However, they can reach a length of 75cm and the maximum known weight is 6kg. Males reach sexual maturity when they are approximately 19cm long, while females mature at a length of approximately 21cm.
The spawning season is from May-August in Europe. Females release eggs into the open water where they float in the surface water due their oily nature. The tub gurnard is a solitary species. They usually live for around 8 years. The maximum known age is 15 years.
Distribution
The tub gurnard is a North-East Atlantic species, which occurs in shelf seas from Norway to Mauritania and as far as Ghana. They can be found in suitable habitats throughout the Mediterranean and Black Sea. These fish are not found in Madeira or the Azores.
The tub gurnard is a bottom-living species to a depth of 20-320 metres on sandy, muddy and gravel soils at temperatures of 8-24 °C.
Threats
There is no reliable data on the populations of this fish. According to the IUCN Red List, the species falls within the “least concern” category, meaning they are not endangered.
However, no population data is available for the central eastern Atlantic. Similarly, populations in the Mediterranean have not been counted or analysed in detail, but it is assumed that the figures are not declining sufficiently for the species to be listed as vulnerable.
The main fishing area for gurnard is the Atlantic. However, there are also smaller fishing areas in the Mediterranean, the Black Sea and the Baltic and North Seas.
Fisheries & Aquaculture
Figures from FAO Fish Stat show that catches have been increasing over the past two decades. In 2000, 2472 tonnes of tub gurnard were caught worldwide. In 2016 this had increased to over 8000 tonnes. These official figures do not include unreported fishing. There are no figures for catches in the Mediterranean, the North Sea, or the Baltic Sea.
The tub gurnard is fished using rods, traps, gillnets, bottom trawls, and bottom longlines. Some of these fishing methods are highly destructive.
Bottom trawls cause considerable damage and destruction to the seabed ecosystem by ‘ploughing’ whole areas with the large rectangular “otter boards” which hold the net open through hydrodynamic forces. In addition, the by-catch rate of this method is very high due to low selectivity in terms of size and species. In bottom longline fisheries, longlines are sunk to the seabed at depths of up to 5,000m and anchored horizontally to the bottom. Is a very non-selective, with a high rate of by-catch.
Fun fact
The gurnard takes their name from the grunting and growling noises they can produce by muscle contraction, vibrating the air in their two-chambered swim bladder. This is also why they are commonly called ‘sea robins’ due to the songs they can produce.
