Energy allocation strategy of skipjack tuna Katsuwonus pelamis during their reproductive cycle

Abstract

The lipid composition of somatic and reproductive tissues was determined for female skipjack tuna Katsuwonus pelamis caught in the western Indian Ocean between latitude 10° N and 20° S and longitude 40° and 70° E. The highest total lipid (TL) contents were in the liver and gonads, with white muscle levels approximately three-fold lower. Three lipid classes dominated: triacylglycerols (TAG), sterol esters and wax esters (SE-WE) and phospholipids (PL). Collectively, these accounted for between 70 and 80% of TLs. Changes in lipid concentrations were evaluated over the maturation cycle. Immature fish had the lowest gonad and liver TL levels; concentrations of TL, TAG, SE-WE and PL accumulated from immature to mature (spawning-capable) phase, reflecting sustained vitellogenic activity of the liver and a transfer of lipids to developing oocytes from the onset of vitellogenesis. Gonado-somatic and hepato-somatic indices were positively correlated with each other and positively related to TL in the gonads and liver. Fulton's condition index and lipid concentrations in muscle did not vary significantly over the maturation cycle; fat content in the main storage tissues was undepleted as the ovary developed. Hence, K. pelamis apparently supports reproduction directly from food intake over the breeding season. In the gonads, reserve lipids (SE-WE and TAG) and sterols were related to batch fecundity but this was not the case for somatic and hepatic tissues. These results suggest that K. pelamis utilizes an income breeding strategy.

Sardine (<em>Sardina pilchardus</em>) spawning in the light of fat content analysis

“…In fact, Zorica et al (2017) found that in the warmer period of the year (June-September), here defined as the feeding phase, sardines consumed higher energy prey such as fish eggs, cladocerans and decapod larvae, resulting in the highest stomach fullness index values. The pattern of acquiring energy reserves before the onset of spawning has previously been reported not only for the sardine (Mustać and Sinovčić 2009, Marin et al 2010, Bandarra et al 2018 and other small pelagics (Hunter and Leong 1981, Cubillos et al 2001, Pacetti et al 2013, but also for many other fish (El Kebir et al 2003, Lloret et al 2008, Grande et al 2016.…”

Skipjack Tuna Availability for Purse Seine Fisheries Is Driven by Suitable Feeding Habitat Dynamics in the Atlantic and Indian Oceans

“…Chlorophyll-a fronts are a mesoscale feature that persist long enough (i.e., weeks to months) to sustain zooplankton production and thus, are known to attract upper trophic level species. As SKJ are both an opportunistic feeder and an income breeder (Grande et al, 2016), we hypothesized that SKJ are also attracted to these features. A time-lag between primary production and SKJ presence was not considered for these features as typically, these fronts frequently change shape and are in constant movement.…”

“…From this review, we estimated that the optimal SST range for SKJ larvae was 27-29 • C. While SST in the Mauritanian upwelling between November and January (below 24 • C) remained outside this range, SST in the Guinea Current was particularly favorable for larval survival (see Figure SI-6A). However, the lack of lipid storage in SKJ muscle and liver tissues (indicative of an income breeder) observed in IO individuals (Grande, 2013;Grande et al, 2016) would severely limit their capacity to effectively use remote feeding grounds for reproduction. If the Guinea Current supports the most suitable SST requirements for larval survival between November and January (and up to March, results not shown), it is possible that locally available food is present to support reproductive activity, albeit in substantially lower quantities than would be provided by productive fronts.…”

“…On average, their reproductive potential is large with around 1 million eggs produced per batch (Grande et al, 2014). SKJ are considered to be income breeders (Grande et al, 2016) meaning that the energy required for reproduction is mainly sourced directly from food intake, as opposed to accumulated energy reserves (McBride et al, 2015). This breeding strategy implies that higher investments in reproduction can be made when food resources are available (Kjesbu et al, 2009).…”

Lipid and fatty acid dynamics in mature female albacore tuna (Thunnus alalunga) in the western Indian Ocean

“…Currently, information on the lipid dynamics involved in reproduction is available only for tropical tunas such as yellowfin ( T . albacares ; [ 3 ] and skipjack ( Katsuwonus pelamis ; [ 23 ]) and other temperate tunas (e.g., in Atlantic bluefin tuna, T . thynnus thynnus ; [ 2 ]), as well as various farmed species [ 24 ].…”