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<p>Intensifying fishing pressure has profoundly altered marine food web structures across global ocean ecosystems. The longnose lancetfish (<i>Alepisaurus ferox</i>) is a widespread deep-sea predator that occupies a mid-trophic position in oceanic ecosystems. Acting both as a predator and as prey for apex predators, it plays a key role in the energy transfer across trophic levels in the open ocean. Changes in its trophic ecology may disrupt the efficiency of this energy transfer, with potential cascading affects higher trophic levels. In this study, we employed a combination of stomach content analysis (SCA), stable isotope analysis (SIA), and total mercury (THg) concentrations to examine the feeding ecology and dietary patterns of individual longnose lancetfish in the tropical western Pacific. Findings from the SCA revealed that longnose lancetfish consume a diverse array of prey, including fish, crustaceans, and other organisms, with notable ontogenetic dietary shifts. Smaller individuals demonstrated a preference for crustaceans, whereas larger individuals favored fish. SIA corroborated these observations, indicating dietary variation associated with growth. Positive correlations were identified between body size and stable isotope values in muscle tissue, suggesting dietary shifts and/or migratory behaviors between the epi/upper mesopelagic layers. Total mercury (THg) analysis revealed clear size-dependent bioaccumulation in longnose lancetfish, with THg levels in muscle and liver strongly correlated with fork length. In muscle, the δ<sup>15</sup>N-THg relationship indicated that trophic position drove mercury accumulation, while contrasting patterns in the liver reflected its role in detoxification and short-term diet integration. The greater niche width and overlap rates in liver tissue compared to muscle tissue in both small and large individuals suggested that short-term feeding habits are more diverse, with increased overlap and competition for resources within the same environment. These findings enhanced our understanding of the feeding strategies and ecological roles of the longnose lancetfish in mesopelagic ecosystems, with potential implications for comprehending long-term changes in these under-researched populations, particularly concerning shifts in dietary patterns and predator–prey dynamics.</p>

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Trophic ecology of the longnose lancetfish based on stable isotope values (δ13C and δ15N), mercury concentrations and stomach contents in the tropical western Pacific Ocean

  • 期刊论文

  • 发表日期：

    2025年9月12日

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  • Yu Ding,
  • Zezheng Li,
  • David Mboglen,
  • Yunkai Li

摘要

Intensifying fishing pressure has profoundly altered marine food web structures across global ocean ecosystems. The longnose lancetfish (Alepisaurus ferox) is a widespread deep-sea predator that occupies a mid-trophic position in oceanic ecosystems. Acting both as a predator and as prey for apex predators, it plays a key role in the energy transfer across trophic levels in the open ocean. Changes in its trophic ecology may disrupt the efficiency of this energy transfer, with potential cascading affects higher trophic levels. In this study, we employed a combination of stomach content analysis (SCA), stable isotope analysis (SIA), and total mercury (THg) concentrations to examine the feeding ecology and dietary patterns of individual longnose lancetfish in the tropical western Pacific. Findings from the SCA revealed that longnose lancetfish consume a diverse array of prey, including fish, crustaceans, and other organisms, with notable ontogenetic dietary shifts. Smaller individuals demonstrated a preference for crustaceans, whereas larger individuals favored fish. SIA corroborated these observations, indicating dietary variation associated with growth. Positive correlations were identified between body size and stable isotope values in muscle tissue, suggesting dietary shifts and/or migratory behaviors between the epi/upper mesopelagic layers. Total mercury (THg) analysis revealed clear size-dependent bioaccumulation in longnose lancetfish, with THg levels in muscle and liver strongly correlated with fork length. In muscle, the δ15N-THg relationship indicated that trophic position drove mercury accumulation, while contrasting patterns in the liver reflected its role in detoxification and short-term diet integration. The greater niche width and overlap rates in liver tissue compared to muscle tissue in both small and large individuals suggested that short-term feeding habits are more diverse, with increased overlap and competition for resources within the same environment. These findings enhanced our understanding of the feeding strategies and ecological roles of the longnose lancetfish in mesopelagic ecosystems, with potential implications for comprehending long-term changes in these under-researched populations, particularly concerning shifts in dietary patterns and predator–prey dynamics.