Interannual variation in quantitative relationships among egg production and densities of larvae and juveniles of the Japanese mantis shrimp Oratosquilla oratoria in Tokyo Bay, Japan

Abstract

To explore which lifestages affect the stock size of young-of-the-year mantis shrimp Oratosquilla oratoria in Tokyo Bay, Japan, we investigated interannual variations in the quantitative relationships among egg production, larval density, and juvenile density. We collected adult females, larvae, and juveniles during monthly field surveys from 2004 to 2007. The interannual trend for the juvenile density index differed from those for egg production and larval density; although indices of both egg production and larval density were high in 2004 and 2007, the juvenile density index was high only in 2007, suggesting high mortality during the pelagic larval stage or the early phase of the postsettlement juvenile stage in 2004. We found that larval settlement started at the end of August and peaked in October, although larvae from the early spawning season (May-June) should have settled in August or earlier. Juveniles were found throughout the bay except in areas where bottom hypoxia occurred, suggesting that hypoxia restricts the spatial distribution of juveniles. Our results suggest that mortality during the early life history fluctuates among years, probably because of changes in environmental conditions in the bay, resulting in interannual variation in the stock size of youngof-the-year juvenile O. oratoria.

Impaired megabenthic community structure caused by summer hypoxia in a eutrophic coastal bay

“…To date, various effects of hypoxia on aquatic organisms have been reported at the individual or population level in terms of mortality (Baden et al 1990;Diaz and Rosenberg 1995), growth (Zhou et al 2001), reproduction (Thomas et al 2006(Thomas et al , 2007Thomas and Rahman 2009), settlement (Baker and Mann 1992;Furota 1996), spatial distribution (Pihl et al 1991;Kodama et al 2006Kodama et al , 2009, and species interaction (Breitburg et al 1997;Shoji et al 2005). Responses to hypoxia differ among taxa.…”

Fishery and life history of spot-tail mantis shrimp, <i>Squilla mantis</i> (Crustacea: Stomatopoda), in the Gulf of Cadiz (eastern central Atlantic)

“…Moreover, changes in environmental conditions could affect mortality in some life-history stages, possibly influencing the relationship between abundance of larvae and juveniles (Kodama et al 2009). However, further studies focusing on the influence of these environmental factors on the S. mantis population are needed in order to determine these relationships.…”

Impacts of shifts in spawning seasonality and size at maturation on the population growth of mantis shrimp in Tokyo Bay

“…Natural selection would be expected to favor a timing of spawning that avoids periods when conditions are unfavorable for spawned offspring (Hare & Cowen 1993). However, in Tokyo Bay, Japan, the current juvenile survival rate for the earliest of 2 seasonal cohorts of mantis shrimp Oratosquilla oratoria appears to be significantly lower than that of the later cohort (Kodama et al 2006a(Kodama et al , 2009.…”

“…Changes in O. oratoria life history and the body-length structure of landings over the past few decades are summarized in Table 1. Kodama et al (2006aKodama et al ( , 2009 suggested that settlement failed only in the spring cohort in the 2000s; it thus appears to be a recent phenomenon. The early cohort spawned by larger females in the spring was able to support the population until at least the 1950s (Kubo et al 1959).…”

“…For these assessments, we developed a size-and age-structured mathematical model. Second, to demonstrate the effect of the increased proportion of smaller-bodied spawners on population dynamics, we estimated recruitment and population growth rates assuming the proportion of mature females had not 180 (Kubo et al 1959) <15 cm at present (Kodama et al 2009) Min. size landed 11 cm in 1980s (Kitahara & Maki 1997) 10 cm in 2000s (Kodama et al 2006b) Min.…”