Modeled buoyancy of eggs and larvae of the deep-sea shrimp Aristeus antennatus (Crustacea: Decapoda) in the northwestern Mediterranean Sea

Abstract

29 Information on the buoyancy of eggs and larvae from deep-sea species is rare but necessary for 30 explaining the position of non-swimming larvae in the water column. Due to embryonic 31 morphology and ecology diversities, egg buoyancy has important variations within one species and 32 among other ones. Nevertheless, it has hardly been explored if this buoyancy variability can be a 33 strategy for deep-sea larvae to optimize their transport beyond their spawning areas. In the 34 northwestern Mediterranean Sea, protozoea and mysis larvae of the commercial deep-sea shrimp 35 Aristeus antennatus were recently found in upper layers, but to present, earlier stages like eggs and 36 nauplii have not been collected. Using a Lagrangian transport model and larval characteristics, we 37 evaluate the buoyancy and hydrodynamic effects on the transport of A. antennatus larvae in the 38 northwestern Mediterranean Sea. The transport models suggested that 75% of buoyant eggs 39 released between 500 and 800 m depth (i.e., known spawning area), reached the upper water layers 40 (0-75 m depth). Then, according to the modeled larval drifts, three spawning regions were defined 41 in the studied area: 1) the northern part, along a continental margin crossed by large submarine 42 canyons; 2) the central part, with two circular circulation structures (i.e., eddies); and 3) the 43 southern part, with currents flowing through a channel. The number of larvae in the most upper 44 layer (0-5 m depth) was higher if the larval transport model accounted for the ascent of eggs and 45 nauplii (81%) instead of eggs reaching the surface before hatching (50%). The larvae reaching the 46 most water upper layer (0-5 m depth) had higher rates of dispersal than the ones transported below 47 the surface layer (deeper than 5 m depth). The results of larval dispersal simulations have 48 implications for the understanding of A. antennatus larval ecology and for management decisions 49 related to the shrimp fisheries in the northwestern Mediterranean Sea. 50 51 Introduction 52 Numerous species have a pelagic larval cycle which links the spawning places to the 53 recruitment areas. Larval cycle is a relatively short time lapse compared to the life cycle of the 54 animal, but it is the phase when large dispersions occur [1]. For benthic species, the distribution of 55 the species mostly relies on the transported larvae which have several mechanisms for positioning 56 themselves in productive and favorable waters for growing and being displaced [2]. Following the 57 adopted strategy, the larvae can be retained on the spawning places or connect to other areas, that is 58 of high interest for species with high commercial value. For that reason, many studies specifically 59 addressed larval drifts in order to determine the efficiency of the fisheries management [3, 4]. 61Aristeus antennatus is a deep-sea shrimp with a high commercial value in the northwestern 62 Mediterranean Sea. Since 1980, the reproductive cycle, biology, and the temporal and spatial 63 dyna...

Modeling the spatiotemporal distribution of the deep-sea shrimp Aristeus antennatus (Crustacea: Decapoda) on the northwestern Mediterranean continental margin crossed by submarine canyons

“…Submarine canyons are environmentally important areas for the megafauna dynamism and the ecology of multiple species. These structures have an effect on the deep-sea species assemblages both within the area itself and on the neighboring open slope (Romano et al, 2017;Tecchio et al, 2013), which populations may be interconnected due to eggs and larval dispersal by water current dynamics, as for the case of Aristeus antennatus (Clavel-Henry et al, 2020). Some benthic communities undertake seasonal and ontogenetic migrations between the canyon area and the open slope, which are detected by observation of the specimen sizes and the distribution of fishing effort throughout the year, as for the case of A. antennatus (Sardà et al, 1997;Sardà et al, 2003a;Tudela et al, 2003) and Merluccius merluccius (Stefanescu et al, 1994).…”