Trophic ecology of Lampanyctus crocodilus on north‐west Mediterranean Sea slopes in relation to reproductive cycle and environmental variables

Abstract

This study examined the population structure, reproductive cycle and feeding pattern of the lanternfish Lampanyctus crocodilus in the Balearic Basin (north-west Mediterranean Sea) from a depth of 450 to 1800 m and at a seasonal scale. Juveniles were mainly located at shallower depths, but also at deepest stations in autumn, while adults mostly inhabited intermediate depths with their centre of population density (CPD) located at 800-1000 m of depth. The migration of adults to deeper depths was detected in late summer to autumn, probably linked to the occurrence of nepheloid layers at c. 1200 m, which in turn enhances the biomass of the zooplankton prey. The diet was mainly based on euphausiids and mysids, with marked seasonal variations both on the upper (450-800 m) and lower (1000-1800 m), where suprabenthic gammariids and pelagic decapods were also dominant. Stomach fullness increased from winter to autumn on the US, while it had a maximum in spring on the LS, in parallel with high consumption of gelatinous zooplankton, which is probably more available after the phytoplankton bloom in late winter. Reproduction occurred in winter, confirmed by the higher percentage of mature females and high gonadosomatic indices (I(G)) at both depth ranges. Hepatosomatic indices (I(H)) showed an inverse trend to I(G) on the US, except in autumn, and was almost parallel on the LS, probably attributable to the migration of adults, which determined different temporal schemes in energy use and storage for reproduction on the US v. LS. Consistent with the different patterns observed at the two depth ranges, environmental drivers of fullness (i.e. feeding intensity) and I(G) (as a proxy of reproductive cycle) differed on the US and LS. The biomass of mysids and euphausiids was the greatest explanatory variables of fullness on the US and LS, pointing to the increasing feeding intensity when a resource was more available. I(H) also explained fullness, suggesting that greater feeding intensity in pre-reproductive periods enabled energy storage in the liver. I(G) was linked directly (i.e. mysids) or indirectly (i.e. surface primary production recorded 2 months before sampling) to food availability, implying a rapid response to vertical food inputs by deep-sea predators. Also, I(G) in L. crocodilus was related to population density, which suggests aggregations for reproduction. Estimates of L. crocodilus trophic levels, and of other accompanying mesopelagic fishes, indicated that the species feed through a continuum spanning the third trophic level, confirming the key role of mesopelagic fishes in transferring organic carbon between trophic levels. Trophic niche segregation among mesopelagic species was pronounced and non-overlapping groups could be distinguished because of the different vertical distribution and migratory behaviour. The study highlights the important role of the benthic boundary layer in sustaining benthopelagic communities in the deep Mediterranean Sea and the need to study the biology of a species throughout its whole ...

Trophic position of lanternfishes (Pisces: Myctophidae) of the tropical and equatorial Atlantic estimated using stable isotopes

“…In any case, the distribution of trophic positions among myctophid species in this and other studies reflects their opportunism in consuming different prey. For example, investigations on B. glaciale of similar sizes to those studied here (30-42 mm) and from different regions showed similar TPA, 3.3 in the subpolar North Atlantic (Petursdottir et al, 2008), between 3.5 and 3.8 in the western Mediterranean (Fanelli et al, 2014;Valls et al, 2014), and 3.3 in our study (Table 2,TPA). Mean values of TPA reported for other species in the western Mediterranean, such as M. punctatum, L. dofleini, D. holti, and L. pusillus (Fanelli et al, 2011(Fanelli et al, , 2014Valls et al, 2014), also differed by less than 0.3 trophic positions of the equivalent estimates of the same species in our study.…”

“…More recent studies based on bulk stable carbon (δ 13 C) and nitrogen (δ 15 N) signatures have determined the trophic levels of several species in the Tasman Sea (Flynn and Kloser, 2012), Mediterranean Sea (Fanelli et al, 2011;Valls et al, 2014), and Gulf of Mexico (McClain-Counts et al, 2017). Scattered information on isotopic values of myctophids collected in general foodweb structure studies or in diet analysis of top predators are also frequently reported (Nilsen et al, 2008;Cherel et al, 2010;Fanelli et al, 2011Fanelli et al, , 2014Colaço et al, 2013;Quintana-Rizzo et al, 2015).…”

Ecology of Benthesicymus tanneri Faxon, 1893 (Dendrobranchiata: Benthesicymidae) from the Mexican Pacific slope

“…It is an important prey of several bony and cartilaginous fishes, birds, and marine mammals (see Balart and Castro-Aguirre, 1995 and references cited therein), and constitutes an important vector in the energy transfer in the marine environment, not only in shallow water but also in the bathyal system. The direct relationship observed between prey abundance and food consumption in bathyal predators Fanelli and Cartes, 2008;Papiol et al, 2014) suggests that B. tanneri and P. planipes coexist at some depth stratum where P. planipes is considerably abundant. Although it is commonly accepted that the distribution of P. planipes is mainly limited to the upper 500 m, at least 250 m shallower than B. tanneri, it is likely that P. planipes is widely distributed at depths below 700 m because: 1) it was found during this investigation in 60% of the hauls made below 700 m, 2) B. tanneri has never been collected shallower than ca.…”

“…It is likely that males are capable of fertilizing more than one female thanks to their faster spermatophore production when compared to eggs production (Mauchline, 1972) and to the ability of females to store spermatophores (Nagaraju, 2011). Bathymetric changes in the sex ratio are also common among deepsea decapod crustaceans (e.g., Chilari et al, 2005;Follesa et al, 2007) and likely result of a combination of feeding and reproductive processes (Puig et al, 2001;Cartes et al, 2008;Fanelli and Cartes, 2008). The bathymetric patterns of sex distribution nevertheless seem a species-dependent adaptive strategy linked to location.…”

Reproductive cycle ofTriplophysa stenura(Herzenstein, 1888) (Balitoridae: Nemacheilinae) from the Yarlung Tsangpo River in the Tibetan Plateau, China

“…Studies of teleost reproduction are needed for fisheries management of endemic species (Abedi, Shiva, Mohammadi, & Malekpour, ; Fanelli, Papiol, Cartes, & Rodriguez‐Romeu, ; Giulianini, Luca, Valli, & Pizzul, ). The growth characteristics and feeding habits of T. stenura were investigated in the Nujiang River, China (Deng, Yue, Chen, Tian, & Liu, ) and there are a few papers concerning the biology of the Triplophysa species from the Tibetan Plateau, China (Liu, Xie, Zheng, & Ji, ; Qi et al., ; Xie, ).…”