24 SEPTEMBER 2023 • WORLD AQUACULTURE • WWW.WAS.ORG In barred sand bass, we closed the life cycle and established the conditions to obtain spawns in captivity, which allowed us to focus on the improvement of conditions during the initial period of the life cycle. The larval period is considered a critical phase of fish development, particularly in marine species with indirect ontogeny (Peña et al. 2003). In these species the larvae suffer transformations in many structures until reaching the juvenile form. These transformations can be very stressful for the larvae and cause malformations or even death. For this reason, it is fundamental to know when these changes occur and relate them to ontogenies of the same or related species in order to make decisions about the optimal administration, size, and composition of inert diets used in the industry. Before this experiment, the traditional protocol designed for the spotted sand bass, a species closely related to the barred sand bass, consisted in giving live food (rotifers) from 2 to 15 DAH, with co-feeding between rotifer and artemia (10-15 DAH), artemia (nauplius and metanauplii) from 10 to 30 DAH with co-feeding between metanauplii and inert food, and total substitution of live food at 30 DAH, giving only inert food after this time (CiveraCerecedo et al. 2007). For barred sand bass, we used a protocol with a mixture of live and inert food starting on 8 DAH and continuing until 26 DAH. By this time the digestive tract has fully formed and is ready to accommodate the complete substitution and be fed with inert food after the 18-day co-feeding period (Figure 7). Finally, the digestive tract of a 30 DAH juvenile is welldifferentiated (Figure 8) complete with digestive enzymes and ready to accept commercial diets. In this work, we documented development in the structure of the digestive tract to provide indications of when different kinds of food could be provided. Reduced use of live food lowers associated costs and risks while reducing the infrastructure necessary for its production. Based on developmental observations, the administration of inert food was successful for this species starting at 8 DAH, when co-feeding with live food. Barred sand bass has the potential to be cultivated because in captivity it can reach around 700 g in a year with fresh food (Rosales-Velazquez et al. 2022). Studies are being carried out to achieve an inert food that offers similar results to those achieved with fresh food. This native species of the Baja California peninsula represents an aquaculture candidate that could be successful in the future. More studies about nutrition and other biological aspects are necessary to establish biotechnologies for its culture. Acknowledgments Thanks to Mexican fellowships for students involved in this project, particularly through Conacyt and Beifi (IPN). Thanks also to CICIMAR (IPN) Baja California Sur, México, for facilities used in the realization of this work. Notes M.O. Rosales-Velázquez*, Laboratory of Experimental Biology, CICIMAR-Instituto Politécnico Nacional, Av. Instituto Politécnico Nacional SN, Playa Palo de Santa Rita, 23096. La Paz, B.C.S. México * Corresponding author: mrosales0400@ipn.mx References Civera-Cerecedo, R., C.A. Alvarez-González, R.E. GarcíaGómez, V. Carrasco-Chávez, J.L. Ortíz-Galindo, M.O. Rosales-Velazquez, T. Grayeb-Del Álamo and F.J. MoyanoLópez. 2007. Effects of micro-particulate diets on growth and survival of spotted sand bass larvae Paralabrax maculatofasciatus at two early weaning times. Journal of the World Aquaculture Society 39 (1):22-36. https://doi.org/10.1111/ j.1749-7345.2007.00132.x INAPESCA (Instituto Nacional de Pesca). 2021. Planes de Manejo Pesquero. Instituto Nacional de Pesca (INAPESCA). Secretaría de Agricultura, Ganadería, Desarrollo Rural, Pesca y Alimentación (SAGARPA). En: https://www.gob.mx/ inapesca/acciones-y-programas/planes-de-manejo-pesquero. Peña-Martínez, R., S. Dumas, M. Villalejo-Fuerte and J.L. OrtízGalindo. 2003. Ontogenetic development of the digestive tract in reared spotted sand bass Paralabrax maculatofasciatus larvae. Aquaculture 219:633–644. https://doi.org/10.1016/ S0044-8486(02)00352-6 Rosales-Velázquez, M.O., J.V. Valdez-Olachea and J.L. OrtízGalindo. 2022. Embryo quality in the voluntary spawning of first-generation (f1) barred sand bass Paralabrax nebulifer kept in captivity. World Aquaculture 2021, Mérida, Yucatán, México, May 24-26, 2022. Roselund G., J. Stoss, C. Talbot. 1997. Co-feeding marine fish larvae with inert and live diets. Aquaculture 155(1-4):183-191. https://doi.org/10.1016/S0044-8486(97)00116-6 FIGURE 7. Larval food protocol for P. nebulifer, showing the time of administration of food and periods of co-feeding. FIGURE 8. Histological cut, 30 DAH, digestive tract completely formed, and showing the liver, stomach (ST), foreguts (FG) pancreas (P) and pyloric caeca (PC). Photo Oscar Rosales, CICIMAR
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