A life-history account ofMacrobrachium spinipes(Schenkel, 1902) (Cherabin) in a large tropical Australian River

Abstract

Rivers in tropical Australia are largely pristine, and ecosystem connectivity is intact, but water resources in northern Australia are under increasing development pressure. A better understanding of the role and life histories of key migratory species is urgently needed to manage the risks posed by development. We investigated the life history of Macrobrachium spinipes (Schenkel, 1902) in the Daly River of the Northern Territory, Australia. We carried out a 13-mo trapping program (2011-2012) at 7 sites along the river between 92 and 405 km from the estuary. We provide the first detailed account of spatial and temporal changes in relative abundance and reproduction, and present information on length at first maturity and Fulton's body condition factor. Reproduction was strongly seasonal and was restricted to the wet-season months of November to April, followed by a recruitment pulse 3 to 4 mo later during the early dry season. Length at first maturity declined as the reproductive season progressed but did not vary significantly with distance from the estuary. Condition was temporally variable and peaked for both sexes immediately after the wet season before declining throughout the dry season. Relative abundance patterns followed a similar pattern. Contrary to results for other Macrobrachium species in rivers of comparable length, we found an increase in the relative abundance of females throughout the river's length during the reproductive season and reproductive effort occurring far upstream, over a restricted time period. This result highlights the importance of maintaining connectivity for reproductive success of this species and further recruitment into these upstream reaches.

Do upstream migrating, juvenile amphidromous shrimps, provide a marine subsidy to river ecosystems?

“…Our data suggested that selective tidal stream transport may play a role, however, more work on this aspect is required. This study builds upon the previous findings on the life history of M. spinipes (Novak et al, 2015(Novak et al, , 2016 and by doing so provides significant insights into the life history and flow ecology of an amphidromous shrimp inhabiting large low land river systems. This is key information for the management of these species should these river systems be impacted by future water resource developments.…”

“…Novak et al. () also found that recruitment of juveniles was unidirectional, from the estuary to the fresh water, and that this recruitment occurred at the end of the wet season and early dry season. The main aim of the present study was to determine the phenology, magnitude and potential marine subsidy of an amphidromous shrimp migration in a large lowland river system.…”

“…Recent work has confirmed that this species is amphidromous (Novak, Garcia, Pusey, & Douglas, 2016) and demonstrated that reproduction occurs during the wet season within fresh water and that there was no evidence of a downstream migration of females to hatch larvae (Novak, Douglas, Garcia, Bayliss, & Pusey, 2015). Novak et al (2015) also found that recruitment of juveniles was unidirectional, from the estuary to the fresh water, and that this recruitment occurred at the end of the wet season and early dry season. The main aim of the present study was to determine the phenology, magnitude and potential marine subsidy of an amphidromous shrimp migration in a large lowland river system.…”

“…Macrobrachium spinipes (Palaemonidae) is a recently described caridean shrimp species (Ng & Wowor, 2011) and occurs throughout tropical Australasia and the Philippines (De Bruyn, Wilson, & Mather, 2004;Short, 2004). Recent work has confirmed that this species is amphidromous (Novak, Garcia, Pusey, & Douglas, 2016) and demonstrated that reproduction occurs during the wet season within fresh water and that there was no evidence of a downstream migration of females to hatch larvae (Novak, Douglas, Garcia, Bayliss, & Pusey, 2015). Novak et al (2015) also found that recruitment of juveniles was unidirectional, from the estuary to the fresh water, and that this recruitment occurred at the end of the wet season and early dry season.…”

Tropical freshwater sciences: an overview of ongoing tropical research

“…Many species of freshwater decapods and some fish species present this type of adaptation (McDowall 2007). In this issue, Novak et al (2015) discuss the life history of a shrimp species from a large tropical river in Australia that follows this pattern. In addition, Crook et al (2015) discuss how the study of otolith microchemistry can aid in understanding the life histories of fish species that inhabit coastal rivers.…”