# Seasonal-Spatial Habitat Variation and Resource Status of Spear Shrimp Mierspenaeopsis hardwickii (Miers, 1878) in the Southern Yellow Sea and East China Sea

## TL;DR

This study examines the seasonal and spatial distribution of the hard spear shrimp in the southern Yellow Sea and East China Sea to support sustainable fishery management.

## Contribution

The study provides new insights into the seasonal migration and resource status of Mierspenaeopsis hardwickii in relation to environmental factors.

## Key findings

- M. hardwickii shows distinct seasonal depth distribution patterns, with aggregations in 20–40 m during spring and summer.
- The annual mean CPUEw and CPUEn were 3624 g·h–1 and 799.4 ind·h–1, respectively.
- Migration routes and nursery areas were hypothesized based on seasonal distribution patterns and environmental conditions.

## Abstract

The hard spear shrimp Mierspenaeopsis hardwickii (Miers, 1878) is a small-sized warm-water species with considerable potential commercial value. In Chinese coastal waters, this shrimp inhabits sandy-mud bottoms at depths of 5–90 m and has a lifespan of only one year. In recent years, overfishing has led to a marked decline in its populations in the East China Sea. The present study aims to characterize the seasonal and spatial distribution patterns of M. hardwickii and assess its current resource status in the southern Yellow Sea and East China Sea, with a focus on relationships with key environmental factors (i.e., depth, water temperature, and salinity). Currently, little is known about the recent resource dynamics or migration routes of this species—ecological information that is critical for the sustainable management and exploitation of small-scale coastal shrimp fisheries.

Mierspenaeopsis hardwickii (Miers, 1878) represents an important economic resource for coastal artisanal fishers and small-scale fisheries operations. However, very little is known about the distribution patterns related to environmental factors and migration routes of M. hardwickii. In this study, we employed research vessels to obtain CPUEw (weight in catch per unit effort) and CPUEn (abundance in catch per unit effort) data in 2018–2019. Our results showed that the largest number was found at 20–40 m in spring and summer, extending in autumn (40–90 m) and shrinking in winter (40–60 m). The scattered distribution pattern of M. hardwickii was observed in spring with sea bottom temperature (SBT) 11–18 °C and sea bottom salinity (SBS) 32–34 and winter (SBT 9–19 °C, SBS 32–35); most individuals were observed in summer (SBT 26–28 °C, SBS 30–31) and autumn (SBT 19–22 °C, SBS 32–35). The annual mean CPUEw and CPUEn were 3624 g·h–1 and 799.4 ind·h–1, respectively. We hypothesize that in spring, most parent cohorts aggregate in Dasha in the southern Yellow Sea, while many cohorts gather in the coastal waters of the East China Sea, with sharply reduced abundance in the offshore deeper waters. In summer, the parent cohorts produced offspring in Lvsi in the southern Yellow Sea, the Yangtze River estuary, and coastal water areas of the East China Sea. In autumn, juveniles in the coastal waters migrated to the offshore water area. In winter, a few individuals were sparsely distributed in the offshore water areas of the southern Yellow and East China Seas, and part of the recruitment in the Taiwan Strait might migrate northward to Yushan and Wentai fishing grounds for the nursery. The present investigations provide baseline data that will enable fishers and policymakers to better manage and conserve this resource for future use.