Chimaera monstrosa, also known as the rabbit fish or rat fish, is a northeast Atlantic and Mediterranean species of fish in the family Chimaeridae. The rabbitfisha is known for its characteristically large head, and small tapering body. With large eyes, nostrils, and tooth plates, the head gives them a rabbit-like appearance, hence the nickname “Rabbitfish”. These fish range in size growing up to 1.5 M long and can age up `to 30 years old.
Morphological Description
The appearance of C. montrosa shares characteristics of its close relatives, sharks. It characteristically has a large head and a tapering body that ends in its whip-like tail, and has a short snout with an overhanging mouth. The top dorsal fin is positioned high on the spine of the fish, and is triangular and tall in height. Positioned in the mid-section of the fish, the spine runs throughout the length of the fish and continuously joins with the upper part of the caudal fin; this dorsal spine is also mildly poisonous that can cause painful stings. One distinguishing feature of the fish to its close relatives is the anal fin, which is distinctly separated from its lancet shaped caudal fin. The color is silver-green with spots of brown. Additionally, they have marmor-white stripes in all directions with a distinct lateral line can be seen clearly on the head. The rabbit fish can grow up to long, and weigh. More specifically when regarding growth of the chimaera species is characterized by a slow-growth rate, and a long life expectancy. In the study, according to the data of the study, the theoretical asymptotic length of this fish is 78.87 with a yearly growth rate of 6.73% per year. With these estimates of growth, the study also suggests the maximum ages of the fish to be 30 years for males and 26 for females with the maturity age of the sample being 13.4 years for males and 11. 2 years for females.
Distribution and habitat
The geographic habitat of the fish has registered around the Mediterranean Sea and the Eastern parts of the Atlantic Ocean. This geographic range starts northwards Morrocco and extends to the northern areas of Norway and Iceland in the Northern North Sea. Within these geological areas, the Chimaera Monstrosa prefers the upper to middle continental slope habitats at depths of 300 m to 500 m. The range of the Chimaera Monstrosa is 50 m to 1,000 m, however, is most abundant between 300 and 500 m. Within these parameters, the waters of the habitats of the Chimaera Monstrosa is most commonly between 4.7 - 8 C°. There have been reports of summer inshore migration of the Chimaera Monstrosa to lay eggs in depth as low as 100 m.
Diet
The Chimaera Monstrosa are classified as benthophagous species. This means that their main diet comprises bottom-feeding invertebrates. This includes animals such as crabs, mollusks, octopuses, sea-worms, and sea urchins. However, studies have also shown that the Chimaera Monstrosa are opportunistic feeders. Comparing the digestive tracts of the species with varying body sizes, the study found that the diet of Chimaera Monstrosa was widely diverse in relation to size. Specimens smaller than 22 cm mainly fed on amphipods, while those with lengths between 22 and 46 cm fed on amphipods and decapods. Larger individuals had a narrow diet spectrum, consuming mainly decapods. Conditioned by predator size group, significant differences in diet were observed between geographical areas and depths. This suggests that despite some degree of prey specialization according to predator size, this deep-water species can change its diet in accordance with the food-restricted environment that characterizes its habitat.
Reproduction
Chimaera Monstrosa are fish that have distinct sex from birth. They reproduce by internal fertilization of male and female. For reproduction, Chimaera Monstrosa displays a small club like structure with a bulbous tip armed with numerous sharp denticles located on the top of the head. This structure is suggested to be used by male fish to grasp the pectoral fin of the female during copulation Chimaera Monstrosa are also Oviparous fish, meaning that the embryo development happens in eggs, and not in the female. Specifically, when referring to the Reproductive tendencies of the Chimaera Monstrosa show sexual segregation in different depths of water, with the female living in lower depth in water. The segregation of sex is attributed to two main factors: the regulation of sperm in males in warmer and shallower waters, and less aggression of sex. For males, they live in water 500-600 m to regulate sperm. For the females, they prefer deeper waters of 800 m, but go up to depths of 500-600 to mate with males. Once mating, they will migrate inshore to lay eggs in the spring of summer.
Conservation
According to the IUCN Red List, Chimaera Monstrosa are categorized as vulnerable. Due to its high levels of lipids, the Chimaera Monstrosa has gained interest in fisheries for its liver oils to manufacture dietary supplements. Aside from its values for oil, the Chimaera Monstrosa is mainly discarded as bycatch product in fishing.
