World Aquaculture - September 2023

52 SEPTEMBER 2023 • WORLD AQUACULTURE • WWW.WAS.ORG 7.1 to 10 mm. During this stage, the growth rate was 0.40 mm day-1 and was expressed by the equation: Y = 0.402x + 6.86; R2 = 0.87 (Figure 4). During this stage, the juveniles showed a pelagic lifestyle, mostly drifting in the water column propelling themselves with the dorsal fin and maneuvering with the pectoral fins. They presented an active feeding strategy based on prey detection, pursuit, and hunting. The second stage of development was identified from day 6 to day 15. The height range during this stage was from 10.1 to 26 mm SL. The highest growth rate was observed during this stage, being 1.41 mm per day, and was explained by the equation Y = 1.414x + 3.83; R2 = 0.95. During this stage of development, an important event occurs in the life history of seahorses. In H. kuda (Choo and Liew, 2006) and H. reidi (personal observation), it is at this time that juveniles begin to make use of the prehensile tail, holding on to objects and spending most of their time swaying by using the pectoral fins to maneuver, indicating a shift to a more sedentary lifestyle. This new behavior modified the feeding strategy of the seahorses, as they stopped spending most of their time swimming in the water column in search of food and began to develop a new “ambush” strategy, in which they waited for prey to pass near them and leaning towards the prey once it approached while attached to a substrate using the prehensile tail. The prey detection and striking distance of the juveniles increased with growth. The third stage was observed from day 16 onwards. It comprised individuals with an LS greater than 26 mm, reaching a maximum height of 41 mm on day 30. The growth rate in this stage was lower than in the previous stage with 0.67 mm day-1 and was explained by the equation Y = 0.669x + 14.104; R2 = 0.76. Study Results The analysis of the allometric growth of the different body segments measured during each developmental stage is presented in Table 1. In stage I, the body dimensions with positive allometric growth (b > 1) were the tail length (b = 1.27), the coronet height (b = 1.22), and the snout length (b = 1.20). The head and the postorbital lengths exhibited isometric growth (b = 1.02 and b = 0.99, respectively). The rest of the dimensions showed negative allometric growth with values of b < 1. During the second stage of development, there was an evident shift in the allometric growth patterns, resulting in a change in body form. The most evident changes were the shift to isometric growth of the trunk length from b = 0.62 to b = 1.00; the length of the tail decreased to a nearly isometric growth, from b = 1.27 to b = 1.08; and the snout length and coronet height changed to negative allometry (b = 0.72 and b = 0.92, respectively). In the case of the other body dimensions, the head length decreased to negative allometric growth. The post-orbital length showed the same growth coefficient, while the rest of the body segments remained with the same types of allometric growth as in the previous stage. The third stage of development showed only two major changes in allometric growth patterns. On the one hand, the snout length growth coefficient decreased from b = 0.72 to b = 0.31 while head height changed from negative allometric growth (b = 0.87) to isometric growth (b = 1.05). The other body segments maintained growth coefficients near isometry (Table 1). These results highlight the importance of snout and tail growth in younger seahorses as part of the survival priorities during the pelagic lifestyle, to develop important traits that characterize this species like holding on to a substrate and ambush feeding. When stage II has been reached, a big adjustment in growth priorities is evident and a general tendency to isometry is observed in all the growth coefficients of the body dimensions, which is accompanied by a reduction in the activity level of the juveniles shifting from a pelagic to a mostly stationary lifestyle. Later, the juvenile stage ends at around 4-5 months of age, with gonadal maturation and incorporation as part of the breeding population. Conclusions The identification of these developmental stages may have important implications for the culture of H. ingens. For instance, a pelagic lifestyle may require a higher prey density to reduce the time spent by the juveniles searching for prey, promoting a higher prey encounter rate and therefore feeding incidence which may translate into higher growth rates. It also may suggest a slower water flow to avoid drifting and energy expenditure by the juveniles while swimming in the water column against the current. Benthic semistationary stages, on the other hand, may require higher water flow to promote prey movement and homogeneous distribution in the water column. It will be interesting to evaluate the development of other biological systems, particularly the visual and digestive systems, during these stages to generate more information that could be useful to adapt culture conditions to the biological and physiological capabilities of these juveniles and to support the previous hypotheses. Notes Renato Peña*, Instituto Politécnico Nacional. Centro Interdisciplinario de Ciencias Marinas. La Paz, BCS. 23096. Mexico. * Corresponding author: Eliezer Zúñiga-Villarreal. INGENS Cultivos Marinos. Mazatlán, Sinaloa. 82110. México 1 ImageJ v2.0 References Choo, C. K. and H. C. Liew. 2006. Morphological development and allometric growth patterns in the juvenile seahorse Hippocampus kuda Bleeker. Journal of Fish Biology 69:426-445. Lourie, S. A., S. J. Foster, E. W. Cooper and A. C. J. Vincent. 2004. A guide to the identification of seahorses. Project Seahorse and TRAFFIC North America. Washington D.C. University of British Columbia and World Wildlife Fund. Ortega-Salas, A. A. and H. Reyes -Bustamante. 2006. Fecundity, survival, and growth of the seahorse Hippocampus ingens (Pisces: Syngnathidae) under semi-controlled conditions. Revista de Biología Tropical 54:1099-1102. Reyes-Bustamante, H. and A. A. Ortega-Salas. 1999. Cultivo del caballito de mar, Hippocampus ingens (Pisces:Syngnathidae) en condiciones artificiales. Revista de Biología Tropical 47:1045-1049. Téllez-Mohedano, V., K. L. Morán-Sánchez, D. Medina-González and D. Voltolina. 1997. Cultivo a nivel piloto del caballito de mar Hippocampus ingens (GIRARD, 1859). Oceanología 3: 98-109. van Snik, G., J. van den Boogaart and J. Osse. 1997. Larval growth patterns in Cyprinus carpio and Clarias gariepinus with attention to the fin fold. Journal of Fish Biology 50: 1339–1352.