Swim Bladder of Farmed Totoaba macdonaldi: A Source of Value-Added Collagen

PurposeFinding strategies to use swim bladder of farmed totoaba (Totoaba macdonaldi) is of utmost need to reduce waste. Fish swim bladders are rich in collagen; hence, extracting collagen is a promising alternative with benefits for aquaculture of totoaba and the environment.MethodsThe elemental biochemical composition of totoaba swim bladders, including proximate composition and amino acid composition were determined. Acid-enzyme solubilisation (PSC) was used to extract collagen from swim bladders and its characteristics were analyzed. The alcalase and papain were used for the preparation of collagen hydrolysates.ResultsSwim bladders contained 95% protein, 2.4% fat, and 0.8% ash (dry basis). The essential amino acids content was low, but the functional amino acids content was high. The PSC yield was high, 68% (dry weight). The amino acid composition profile, electrophoretic pattern, and structural integrity analyses of the isolated collagen suggested it is typical type-I collagen with high purity. The denaturalization temperature was 34.5 °C, probably attributable to the imino acid content (205 residues/1000 residues). Papain-hydrolysates (<3 kDa) of this collagen exhibited higher radical scavenging activity than Alcalase-hydrolysates.ConclusionsSwim bladder from farmed totoaba is an ideal raw material for producing high-quality type-I collagen and a viable alternative to conventional collagen sources.Statement of NoveltyTo our knowledge, this paper is the first to examine the composition and characteristics of collagen of swim bladder from Totoaba macdonaldi. Although the processing currently wastes bladders, this study showed that they could be a potential source for producing high-quality type-I collagen.

Vaquita: beleaguered porpoise of the Gulf of California, México

The vaquita (Phocoena sinus), an endemic porpoise of the Gulf of California, México, was first described scientifically in 1958, from three skulls. It is considered a sister taxon of an ancestor of the Southern Hemisphere Burmeister’s porpoise (P. spinipinnis) and spectacled porpoise (P. dioptrica), a case of antitropical distribution and speciation. Vaquita in modern times seem to have existed largely in waters 10 to 30 m deep of the very northern Gulf of California, and may have already existed in relatively low numbers by the 1950s and 1960s. The external appearance of the vaquita was not described until the late 1970s, and not until the 1980s and 1990s did additional information about ecology and biology emerge. Those studies and more recent shipboard and aerial visual line transect surveys, as well as stationary and boat-towed acoustic arrays, mapped occurrence patterns and approximate numbers in greater detail than before. The first credible estimates of abundance appeared in the 1990s, with numbers in the mid-hundreds and declining. While several reasons for the decline were originally postulated, mortality due to entanglement in nets has been established as the only known cause of decline, especially due to bycatch in large-mesh gillnets set for the endangered croaker fish totoaba (Totoaba macdonaldi). This fish is prized in China for human consumption of its swim bladder, generally ground up for purported therapeutic purposes. An extensive, lucrative fishery for totoaba, now illegal for many decades, has existed since at least the 1920s, and has recently increased. Although there have been laudable attempts to stem or halt totoaba fishing, these have largely been unsuccessful, and as of this writing the vaquita is on the brink of extinction. However, rapid concentrated action against illegal fishing with gillnets may yet save the species, and hope (with attendant action) must be kept alive. This overview is followed by an appendix of a previously unpublished popular essay by K.S. Norris describing when, where, and how he first discovered the species, and subsequent early work relative to this newly-described porpoise.

Growth, thermal preference and critical thermal maximum for Totoaba macdonaldi: effect of acclimation temperature and inclusion of soybean meal in the diet

We studied the interaction effect between temperature 23 and 26°C, and replacing fishmeal for soybean meal (SBM): 32, 43, and 56% vs. a diet control on culture performance, thermal behavior, and critical thermal maximum (CTMax) of juvenile Totoaba macdonaldi. Fish were fed to apparent satiation three times daily for 61 days. The results showed that temperature had a significant effect (P < 0.05) on weight gain, percent weight gain, and specific growth rate, which were all higher in fish acclimated at 26°C. The preferred temperature ranged between 26.4 and 27.7°C, significantly influenced by acclimation temperature (P < 0.05) but not by diet. CTMax was influenced by acclimation temperature and SBM in the diet. Fish resistance decreased when the percent SBM in the diet was higher. Information on biological indicators for T. macdonaldi adds to the knowledge of a key Mexican species. Our study demonstrated that the use of SBM as an alternative to fishmeal in the diet and the interaction with temperature as a factor could affect this species' performance.

Viability of the vaquita, Phocoena sinus (Cetacea: Phocoenidae) population, threatened by poaching of Totoaba macdonaldi (Perciformes: Sciaenidae)

Introduction: Despite extensive science-based conservation policy recommendations, with fewer than 20 individuals remaining, the vaquita (Phocoena sinus) -endemic to the Gulf of California- is the world’s most endangered marine mammal due to incidental catch in fishing nets and whether it can recover is unclear. Objective: Assess expectations for vaquita over the next two decades. Methods: We identified factors affecting the vaquita, constructed life tables, derived demographic parameters for different scenarios and conducted a population viability analysis using stochastic age-structured matrix Leslie models. Results: Analytical results indicate that the vaquita net growth rate is particularly sensitive to juvenile survival. We find that intensive, ongoing bycatch in gillnets used to poach totoaba (Totoaba macdonaldi) over the past decade brought the vaquita population to its current critically low size. Currently this seems to be exacerbated by demographic stochasticity and a potential Allee effect. Conclusions: If totoaba poaching is eliminated immediately, demographically, vaquita can recover; its long-term survival will depend on its uncertain genetic status, although a recent study found encouraging results in this regard.

Influence of sex and maturity state on trace elements content in liver and muscle of the SciaenidaeTotoaba macdonaldi

BackgroundThe fishTotoaba macdonaldiis endemic to the Upper Gulf of California. Its migratory movements involve sites with high levels of trace elements in the environment that can accumulate in tissues. In this study, lead (Pb), copper (Cu), cadmium (Cd), zinc (Zn) and iron (Fe) concentrations in male and female totoaba liver and muscle were quantified at various sexual maturity stages along the species’ geographic distribution.MethodsGeneralized linear models were used to explore associations between trace element concentrations and season of the year, sex/maturity stage, and total fish length.ResultsNo detectable Pb concentrations were recorded in liver or muscle; Cu, Cd, Zn and Fe contents in totoaba liver and muscle were typical of fish inhabiting areas with no contamination issues and are within international maximum permissible levels for human consumption. Variations in the content of Cd, Cu, Zn and Fe in liver of totoaba seem to be more related to the feeding and reproductive physiology of this species than as result of environmental exposure. Results suggest that consumption of totoaba muscle does not pose a public health risk. Furthermore, depending on the sex/maturity stage of totoaba, this fish’s muscle may provide approximately 70% Cu, 60% Zn and 100% Fe of the recommended dietary reference intake.