Proliferation of elongate fishes in the deep sea

Abstract

It was hypothesized that energetically efficient anguilliform swimming and axial elongation in fishes is favoured in the deep sea and predicted that the degree of elongation of the body form of fishes would increase with depth. An index of fish shape was derived from the relationship between length and mass. This was combined with data on abundance of c. 266 fish species from 389 research trawl tows made at depths of between 300 and 2030 m in the north-east Atlantic Ocean. The degree of elongation of the fish increased with depth to c. 1250 m before levelling off. The strength of this phenomenon varied between higher level taxa, being most apparent in the Gadiformes and Osmeriformes, and weak or absent in the Perciformes and Selachimorpha. The advantage of efficient elongate body forms may explain why certain taxa such as the grenadiers (Macrouridae) have dominated the deep sea, some have restricted depth ranges, e.g. the sharks, skates and rays, and others are almost entirely absent, e.g. the flatfishes (Pleuronectiformes).

Changes in key traits versus depth and latitude suggest energy‐efficient locomotion, opportunistic feeding and light lead to adaptive morphologies of marine fishes

“…Locomotion is energetically taxing and can be made more difficult by undersea currents and variation in water viscosity, all of which increase energy requirements in the already resource‐limited environment that occurs at deeper depths (Langerhans, ). Our hypothesis of an increase in fin‐base‐to‐perimeter ratio, elongation and total body length with increasing depth was supported by the data and reflected an apparent shift towards traits that enable energy‐efficient locomotion (Neat & Campbell, ). At deeper depths, we found fishes had a greater mean total body length, and a more ‘anguilliform’, elongate body shape, with a longer average fin‐base.…”

“…At deeper depths, we found fishes had a greater mean total body length, and a more ‘anguilliform’, elongate body shape, with a longer average fin‐base. All of these morphological traits are linked to an undulatory swimming method (see Neat & Campbell, ; Webb, ). Fishes that swim using undulation generate a wave that propagates down the body or fins.…”

Trophic interactions of fish communities at midwater depths enhance long-term carbon storage and benthic production on continental slopes

“…Mean biomass per length unit was estimated from modal lengths and abundances by applying length -weight relationships derived from repeated trawl surveys in the Rockall Trough region [35], or from www.fishbase.org [34], and calculated by species and depth. Data were then binned into log 5 mass classes.…”

Ecogeochemistry potential in deep time biodiversity illustrated using a modern deep-water case study

“…While much of the continental slopes are relatively unexplored, demersal fish faunas of the northeast Atlantic continental slope have been surveyed extensively [14][15][16][17], and are among the best known globally. Continental slope communities are strongly structured by depth, and community composition and functional traits vary across depth gradients [18], providing ecological structure that can be investigated using ecogeochemical methods. 3.…”