Long‐term interannual variability in larval dispersal and connectivity of the Norway lobster (Nephrops norvegicus) around Ireland: When supply‐side matters

Abstract

Dispersal of meroplankton larvae in the ocean is a key process which determines larval supply to areas of suitable habitat and enables connectivity between populations, particularly for nonmigratory species. Our objective was to use a biophysical larval transport model to create a time series (2000–2019) of larval retention, dispersal distance and connectivity estimates for the commercially important Norway lobster (Nephrops norvegicus) on mud grounds off Ireland. Where time series of population estimates were sufficiently long to conduct analysis, we also investigated if larval dispersal indices could be used to predict variations in adult density, after a lag period, hypothesising that this would only apply to grounds with consistently low larval supply. Grounds off Ireland had varying characteristics related to their ability to retain and exchange larvae which was influenced by the local hydrodynamic regime and spatial isolation from other grounds. Larval supply was consistently low on the Aran grounds to the west of Ireland, which have experienced abundance declines in the past. The time series of modelled larval dispersal indices at the Aran grounds was linked to empirical adult burrow densities with a 3‐year lag. Whereas the western Irish Sea, which has consistently high larval supply, showed no such relationship. Models can provide important larval recruitment information early in the life cycle for species of commercial or conservation importance.

Limited spatiotemporal larval mixing of the Norway lobster from no‐take marine protected areas in the northwestern Mediterranean Sea

“…This depth range has to be readapted once an observed vertical profile of the larva distribution is reported for our study area. Nonetheless, this depth range would also be in line with other studies on the Norway lobster using larval transport modelling (McGeady et al, 2022; Melaku Canu et al, 2020).…”

Daily age, growth rate, and pelagic larval duration of commercially important snapper species in Abrolhos National Marine Park

“…This variation is expected because, even in nature, many species have long pre‐competent phases or plasticity in larval duration, which are often related to environmental conditions, resulting in high PLD variation within a species (Selkoe & Toonen, 2011). Furthermore, the nutritional resources available to larvae during their pelagic phase can also cause variations in PLD (Faurby & Barber, 2012; Lucas, 1982; McCormick & Molony, 1995; McGeady et al, 2022). Although within‐species variability in PLD described in the literature and this work was found, on average, the observed PLDs are compatible with other lutjanid species captured by light traps (Zapata & Herrón, 2002), indicating the influence of the family's life‐history patterns.…”

Genetic and particle modelling approaches to assessing population connectivity in a deep sea lobster

“…The data was used in several ways, (1) to extract the data pertaining to that of the pelagic larval phase per season (December to February-summer; March to May-Autumn; June to August-Winter; September to November-Spring), (2) to track the movement of the particles which could then provide details of the approximate number of generations needed for connectivity among dispersed locations, and (3) enumerating connectivity by calculating the total number of particles arriving at each SCI sample area from each source sample area over the modelling period (i.e., source-sink dynamics). Our use of hydrodynamic models for simulating larval dispersal draws on well-established research for a wide range of marine species e.g., [109][110][111][112] . However, our approach to the application of the modelling differs in that we are interested in multigenerational connectivity which is consistent with the biological process for migration of genes within a wide ranging population, and it ensured that inter-annual variability in hydrodynamic processes were incorporated into the modelled outcomes, whilst also ensuring there was enough time for particle dispersal to assess possible long distance multigenerational dispersal.…”