Feeding ecology and life-history strategy of nesting males in a fish with long parental care, Lusitanian toadfish (Halobatrachus didactylus, Batrachoididae)

Abstract

The Lusitanian toadfish,Halobatrachus didactylus, like other batrachoidids, is a benthic fish species with nesting behaviour during the breeding season. During this prolonged period it engages in mating activities and remains in the nest providing parental care. It is not known whether males feed while providing parental care but it is likely that their limited mobility may restrict their diet and influence their fitness. As a consequence, egg cannibalism could occur as a life-history strategy. The aim of the present study is to ascertain the feeding behaviour of nesting males, in comparison to mature non-nesting males, and to identify potential life-history traits related to egg cannibalism. Nest-holders were sampled from artificial nests placed in an intertidal area of the Tagus estuary, only exposed during spring low tides. The diet of nest-holders was compared with that of non-nesting mature males from the same area, captured by otter trawl. The present study demonstrates that despite their constrained mobility nest-holders feed during the breeding season, although in a more opportunistic fashion than non-nesting males. Nest-holders showed a generalist feeding behaviour, with a more heterogeneous diet. Egg cannibalism was not related to male condition, paternity or brood size but showed a higher incidence early in the season when water temperatures were lower. The results suggest a possible seasonal trade-off strategy between care and energy recovery, triggered by environmental factors, where under unfavourable conditions to sustain viable eggs the male may recover energy by eating eggs, thus benefiting future reproductive success, later in the season.

Fine-scale behaviour of the Lusitanian toadfish assessed in situ with the AccelTag

“…AccelTag proved to be a powerful tool to assess and monitor the fine-scale behaviour of a resident estuarine fish. In terms of ecological data obtained with AccelTag, the main findings are concordant with results obtained with other works that used distinct methodological approaches to study the Lusitanian toadfish foraging behaviour [21][22][23][24]. When comparing to other available tools (see [5] for further discussion) such as data storage tags with accelerometer sensors [6,7], and even more recent acoustic transmitters equipped with three-axis accelerometer sensors [8-11, 25, 26], the AccelTag has the advantage of being able to process the fine-scale acceleration information autonomously and acoustically transmit the correspondent behaviour.…”

“…The species is more active in late spring and early summer, concurring with the reproductive period [17,18]. It occupies a top position on the food web [19] and exhibits a high degree of trophic plasticity, adapting its feeding habits to prey availability reproductive needs [17,20,21]. The specimens of this species remain most of the time buried or concealed in crevices, adopting a camouflage and ambush mode of predation [22,23].…”

Parent–offspring cannibalism throughout the animal kingdom: a review of adaptive hypotheses

“…However, numerous studies have not detected any relationship between cannibalism and brood parentage or cuckolder pressure [e.g. male common goby (Svensson et al ., 1998; Vallon & Heubel, 2016); male spottail darter, Etheostoma squamiceps (Bandoli, 2006); male sand goby (Svensson & Kvarnemo, 2007; Lissåker & Svensson, 2008); male Lusitanian toadfish (Félix et al ., 2016); male and female Neolamprologus caudopunctatus (Cunha‐Saraiva et al ., 2018)].…”

“…Some correlational studies have found inconclusive or even opposing evidence for the energy reserves hypothesis [e.g. male sand goby, Pomatoschistus minutus (Klug et al ., 2006); male plainfin midshipman fish (Bose et al ., 2015); male Lusitanian toadfish, Halobatrachus didactylus (Félix et al ., 2016)], and some experimental diet manipulations have also failed to influence parent–offspring cannibalism [e.g. male three‐spined stickleback (Belles‐Isles & Fitzgerald, 1991); male fantail darter, Etheostoma flabellare (Lindström & Sargent, 1997); male sand goby (Kvarnemo, 1997); male beaugregory damselfish, Stegastes leucostictus (Payne et al ., 2002)].…”

Boat noise impacts Lusitanian toadfish breeding males and reproductive outcome

“…Although we used playbacks and not real boat passages, our field experiment mimicked a typical pattern of noise exposure by common ferry boats and small outboard engine boats in the Tagus estuary, pointing to marked detrimental fitness effects, even with only up to 2 weeks of noise exposure from two boat types and without the possible effect of low frequencies below c. 100 Hz. Toadfish parental males will likely experience a higher noise exposure from boating as parental care takes up to 3 months during which males stay in the nest to care for the eggs and defend the nest from takeovers or egg predation (Félix et al, 2016). Also, depending on the breeding site, they will be exposed to more boat noise sources, such as large cruisers, cargo vessels and dredgers (Vieira et al, 2021b), which tend to be louder (Hildebrand, 2009) and likely more impacting (Putland et al, 2018), not to mention other forms of anthropogenic noise (Vieira et al, 2021b).…”