Effects of constant light on haematological parameters of cultured rainbow trout (Oncorhynchus mykiss) in the Southern Hemisphere

Abstract

California halibut Paralichthys californicus is an important commercial species with high aquaculture potential in Baja California Sur, Me´xico. To optimize the feeding process using live prey and/or inert diets, we evaluated alkaline proteases, pepsin, trypsin, chymotrypsin, leucine aminopeptidase, lipase, a-amylase, and acid and alkaline phosphatase activities on starved larvae and larvae fed live prey. Highest activities were observed for alkaline protease, trypsin, chymotrypsin, leucine aminopeptidase, and alkaline phosphatase in feeding larvae than starved larvae on day 4 after hatching. At day 5, a sizeable increase in all enzymatic activities was detected in feeding larvae. Alkaline protease, trypsin, chymotrypsin, and alkaline phosphatase decreases progressively from day 5 until day 18. At day 18, a slight pepsin activity was observed. This was considered an indicator of the start of digestive system maturation. We concluded that total enzymatic equipment for this species is complete between day 18 and 30 after hatching. Based on this evidence, early weaning from live prey to inert feed would be possible at this time.

Changes of Digestive Enzymatic Activity on Yellowtail Snapper (Ocyurus chrysurus) During Initial Ontogeny

“…Our results are similar to those reported for other species, where the digestive process in fish larvae in alkaline conditions usually begins with the contribution of pancreatic and cytosolic enzymes (Xiu et al, 2009). In this context, the presence of alkaline proteases, trypsin and specific chymotrypsin, detected in the first days following the mouth opening was similar to the results of carnivorous fish such as P. californicus (Alvarez-González et al 2006), P. maculatofasciatus (Alvarez-González et al 2008) and C. undecimalis (Jiménez-Martínez et al, 2012), where the earliest activity corresponds to alkaline proteases, as the acid protease activity is closely related to the occurrence of a functional stomach which takes place later (Moyano et al, 1996;Alarcón-López & Martínez-Díaz, 1998;Zambonino Infante & Cahu, 2001;Alvarez-González et al 2008;Jiménez-Martínez et al, 2012).…”

“…In the present work, the activity of pepsin of O. chrysurus peaked at 34 DAH, this is in similar to results from other marine fishes such as Solea senegalensis (Martínez et al, 1999), P. californicus (Alvarez-González et al, 2006), P. maculatofasciatus (Alvarez-González et al, 2008), Scophthalmus maximus (Tong et al 2011) y C. undecimalis (Jiménez-Martínez et al, 2012. The absence of a functional and morphologically different stomach during the first days after hatching is common for marine fish larvae.…”

“…Also after the onset of exogenous feeding, the activity of leucine aminopeptidase is modulated by the diet, as the above mentioned by trypsin, because it shows a steep rise with slight fluctuations caused by the evolution thereof. Likewise, this increase can be explained by the different nutrient composition of rotifers and Artemia integrated into their diet, which, as mentioned above are not the most suitable for the culture of many of the marine fish species (Moyano et al, 1996;Alvarez-González et al, 2006;Alvarez-González et al, 2008;Xiu et al, 2009). …”

“…The bottleneck in the commercial culture of this species is a high mortality in the early life stages therefore nutrition studies in larvae and juveniles are vital for a commercial scale production (Moyano, Díaz, Alarcón, & Sarasquete, 1996). Drawbridge, Jiménez-Martínez et al, 2012) considering that the feed efficiency depends on fish physiological capabilities for transforming nutrient intake (Alvarez-González et al, 2006;Xiu et al, 2009;Babaei, Kenari, Nazarí, & Gisbert. 2011).…”

“…Thus, the activity of digestive enzymes from hatching to juvenile period can be used as an indicator of nutritional status in early life stage (Moyano et al, 1996;Álvarez-González et al, 2006;Galaviz et al, 2011;Gisbert, Fernández, & Álvarez-González, 2011;Babaei et al, 2011). Several ontogeny studies on digestive physiology during larviculture have been reported as Moyano et al (1996) in Sparus aurata; Zambonino-Infante and Cahu (2001) in Dicentrarchus labrax; Alvarez-González et al (2006) in Paralichthys californicus, Alvarez-González et al (2008) in Paralabrax maculatofasciatus; Xiu et al (2009) in Miichthys miiuy and Jiménez- Martínez et al (2012) in Centropomus undecimalis; whose concluded that larvae before the first exogenous feeding may already be able to absorb the nutrients from the diet as well as changes in the enzymatic activity of various digestive enzymes is very similar to other strictly carnivorous marine fishes. Additional studies have been conducted on the early development of the Menidia menidia and Odontestes bonarensis digestive system to determine the time of maximum enzyme activity (Toledo et al, 2011).…”