WWW.WAS.ORG • WORLD AQUACULTURE • SEPTEMBER 2025 33 being. The findings revealed that wild lumpfish consistently had bright orange livers, suggesting a link between liver pigmentation and overall well-being (Photo 2). This discovery led to a study by Eliasen et al. (2020), which demonstrated that liver color—ranging from pale to bright orange to dark reddish-brown—reflects key biological differences and can function as an OWI and help farmers improve lumpfish welfare and survival (Figure 1). The study found that lumpfish with bright orange livers had higher levels of carotenoid pigments like astaxanthin and canthaxanthin, essential for immune function and overall health. In the wild, lumpfish obtain these pigments naturally from their diet, which is rich in crustaceans. However, in salmon cages, they rely on formulated feed, which may not always provide enough of these important nutrients. On the other hand, lumpfish with dark reddish-brown livers had lower energy reserves, particularly stored fats (lipids), which play an important role in their overall condition and welfare (Figure 2). These fish were likely under nutritional stress, causing them to break down their own liver fat for energy. The study also found that lumpfish with darker livers had smaller livers in relation to their body size, further linking liver color to overall condition and energy storage. Changes in liver color can therefore provide valuable insights into lumpfish health. A transition from bright orange to dark reddish-brown often signals nutritional deficiencies or metabolic stress, while a change to pale livers may indicate underlying disease. Regular liver color assessments offer a practical OWI, helping farmers make decisions on feeding strategies and husbandry practices. By closely tracking these shifts, farmers can intervene early to improve lumpfish welfare, survival rates, and their overall efficiency as cleaner fish. Body Condition The body condition of fish can be estimated using standard length-to-weight relationships to evaluate their growth and condition. Traditionally, the body condition of lumpfish in salmon cages has been based on length-weight relationships from lumpfish in salmon cage environments (Gutierrez Rabadan et al., 2021, Eliasen et al., 2020, Rey et al., 2021, Engebretsen et al., 2024). However, from the onset of welfare monitoring in the Faroe Islands, farmers and researchers relied on data on lengths and weights of wild lumpfish, provided by the Faroe Marine Research Institute from their longstanding pelagic surveys. This reference has played an important role in identifying discrepancies in growth patterns, highlighting areas for improvement in husbandry and welfare practices. A study by Østerø et al. (2024) found that wild lumpfish caught around the Faroe Islands exhibit a positive allometric growth pattern, meaning they gain proportionally more weight as they grow longer. In contrast, lumpfish in salmon cages displayed slightly negative allometric growth, where weight did not increase in proportion to length. Additionally, other commonly used standard weight references for farmed lumpfish showed an even more pronounced negative allometric growth pattern. These differences in growth patterns are displayed in Figure 3. The differing growth patterns may be due to the long-standing use of wild lumpfish as a reference for body condition in the Faroe Islands. This ongoing comparison may have contributed to efforts to maintain growth patterns closer to those seen in the wild. The study found that a significant proportion of lumpfish in salmon cages were underweight or emaciated compared to wild lumpfish. Figure 4 illustrates the proportional distribution of lumpfish across three body condition categories—good condition, underweight, and emaciated—using (a) a lengthweight regression by Gutierrez Rabadan et al. (2021) and (b) a regression based on wild lumpfish from the study by Østerø et al. (2024). The distribution based on wild lumpfish aligns well with observations from the Faroe Islands, where lumpfish generally display good body condition in hatcheries and at deployment but where body condition declines after deployment in salmon cages. Incorporating body condition standards based on wild lumpfish, can help farmers better to detect underweight or emaciated lumpfish (Photo 3). Regular monitoring of growth patterns allows for early intervention when signs of poor health arise, ultimately improving survival rates and the effectiveness of lumpfish as cleaner fish. Using wild lumpfish as a reference for body condition ensures that farmed lumpfish are assessed against their natural growth patterns, offering a more accurate benchmark for detecting and addressing poor body condition. (CONTINUED ON PAGE 34) TOP, FIGURE 1. Liver color scoring system. From Eliasen et al. 2020. BOTTOM, FIGURE 2. Lipid content (%) in relation to liver color. From Eliasen et al. 2020.
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