# Comparison of the Burrowing Ability of Different Groups of Manila Clams (Ruditapes philippinarum)

## TL;DR

This study compares how well different groups of Manila clams can burrow into various substrates, finding that the zebra strain group and smaller clams burrow more efficiently.

## Contribution

The study is the first to compare burrowing abilities of different Manila clam groups under varying substrate and sowing conditions.

## Key findings

- The zebra strain group showed the highest burrowing rate compared to Fujian and Laizhou groups.
- Clams with a shell length of 1.0 cm burrowed more efficiently than larger clams.
- Decentralized sowing mode initially improved burrowing rates but had no significant long-term effect.

## Abstract

The Manila clam (Ruditapes philippinarum) is the world’s second most important bivalve mollusk to be commercially farmed, and the Manila clam is a species that lives in the substrate. The burrowing ability is of great significance for clams to protect themselves from predators and water currents. At present, the clam groups involved in aquaculture in the northern sea of China include the Fujian group, the Laizhou group, and the zebra strain group. In this study, we investigated the burrowing ability of different Manila clam groups for the first time by comparing the burrowing ability of varying sizes within the Fujian, Laizhou, and zebra strain groups across different substrate sizes. The impact of the sowing mode on their burrowing ability was also explored. The results indicated that the burrowing ability of different groups and clam sizes varied, with the zebra strain group having a relatively stronger burrowing ability. In addition, the particle size of the substrate and the sowing mode also had an impact on the burrowing efficiency of clams from the three groups. This work will be of great significance for the selection of seedling groups in the aquaculture of clams.

Clams from the Fujian group, the Laizhou group, and the zebra strain group were used in this investigation; their shell lengths were 1.0 cm, 1.5 cm, and 2.0 cm, respectively. Tests were conducted on substrates with particle sizes ranging from 151 to 180 µm, 181 to 250 µm, 251 to 425 µm, and 426 to 850 µm. Both centralized and decentralized sowing modes were used. According to the findings, the clams with the 1.0 cm shell length had the highest burrowing rate and the lowest ET50. From 0 to 120 min, the burrowing rate of the zebra strain group was higher than that of the other groups. Clams with shell lengths of 1.0 cm and 1.5 cm had similar burrowing rates at the end of the test, with the zebra strain group having the highest burrowing rate. Manila clams burrowed more quickly when the substrate’s particle sizes were between 181 and 425 µm. The clam burrowing rates in the decentralized sowing mode were high during the first 20 min of the test, but at the end of the test, there was no significant difference between the two sowing modes (p > 0.05). In summary, there were differences in the burrowing ability among the three groups. The clams with a shell length of 1.0 cm in the three groups had a higher burrowing efficiency, and the decentralized sowing mode was more conducive to the clams quickly burrowing into the substrate.