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Growth and haematological parameters are used in aquaculture as indicators of the health of cultivated fish in response to changes in diet and the physicochemical conditions of the water. In this study, the physiological status of Totoaba macdonaldi was evaluated based on growth, haematological parameters and blood chemistry in response to two temperatures (23°C and 26°C) and the partial replacement of fishmeal with soybean meal (SBM—32%, 43% and 56%). In total, 288 fish were distributed among a control group and treatments in a 2 × 4 experimental design with three replicates. The diet was provided to apparent satiety three times a day for 61 days. Temperature significantly affected the final average weight of the fish acclimated to 23°C or 26°C ( p < 0.05). The highest final average weight (264.2 ± 7.9 g) was recorded in fish acclimated to 26°C and fed a diet with 43% SBM, and the Fulton condition index ranged from 0.98 ± 0.01 to 1.05 ± 0.12. The albumin and aminotransferase enzyme concentrations and the albumin:globulin ratio were affected by the acclimation temperature ( p < 0.05). The temperature–diet interaction affected the concentrations of leukocytes, albumin and triglycerides. Diets containing SBM significantly affected ( p < 0.05) the concentrations of leukocytes, total proteins, albumin, globulins, glucose, triglycerides, aspartate and alanine aminotransferases, as well as the albumin:globulin ratio. Increases in these indicators were observed in fish fed diets with higher percentages of SBM. The results show that replacing fish meal with more than 32% SBM could negatively affect health‐related blood parameters in T. macdonaldi , with more pronounced effects when a diet–temperature interaction is present. These findings highlight the need for further research to evaluate the use of SBM in T. macdonaldi diets and its effect on their physiological performance under different thermal conditions.

Totoaba ( Totoaba macdonaldi ), an ancient fish endemic to the Gulf of California (Sea of Cortez), has faced significant challenges in recent decades. Since 1990, several serious issues have been raised regarding conservation, fisheries, and sustainable aquaculture. In the search for solutions for sustainable Totoaba aquaculture in Mexico, research from natural and social science disciplines has converged to give explanations and proposals. In light of the scientific findings, publications have brought insights into biology, immunology, ecology, nutrition, reproduction, genetics, policies, and social aspects. This review synthesizes and integrates the current state of knowledge across these fields, offering a comprehensive overview of Totoaba research and highlighting prospects, with a particular emphasis on sustainable aquaculture practices and long-term conservation strategies.

The vaquita (Phocoena sinus) is the world's most endangered marine mammal with approximately 245 individuals remaining in 2008. This species of porpoise is endemic to the northern Gulf of California, Mexico, and historically the population has declined because of unsustainable bycatch in gillnets. An illegal gillnet fishery for an endangered fish, the totoaba (Totoaba macdonaldi), has recently resurged throughout the vaquita's range. The secretive but lucrative wildlife trade with China for totoaba swim bladders has probably increased vaquita bycatch mortality by an unknown amount. Precise population monitoring by visual surveys is difficult because vaquitas are inherently hard to see and have now become so rare that sighting rates are very low. However, their echolocation clicks can be identified readily on specialized acoustic detectors. Acoustic detections on an array of 46 moored detectors indicated vaquita acoustic activity declined by 80% between 2011 and 2015 in the central part of the species' range. Statistical models estimated an annual rate of decline of 34% (95% Bayesian credible interval -48% to -21%). Based on results from 2011 to 2014, the government of Mexico enacted and is enforcing an emergency 2-year ban on gillnets throughout the species' range to prevent extinction, at a cost of US$74 million to compensate fishers. Developing precise acoustic monitoring methods proved critical to exposing the severity of vaquitas' decline and emphasizes the need for continual monitoring to effectively manage critically endangered species. La vaquita (Phocoena sinus) es el mamífero marino en mayor peligro de extinción, con aproximadamente 245 individuos existentes en 2008. Esta especie de marsopa es endémica de la parte norte del Golfo de California, México, e históricamente su población ha declinado por causa de la captura accidental en redes agalleras. La pesca ilegal con redes agalleras de un pez en peligro, la totoaba (Totoaba mcdonaldi), ha resurgido recientemente en la zona de distribución de la vaquita. El lucrativo y oculto mercado de fauna con China, por la vejiga de la totoaba, probablemente ha incrementado la mortalidad por captura accidental de la vaquita en una cantidad desconocida. El monitoreo preciso de la población por medio de censos visuales es difícil porque las vaquitas son difíciles de ver por naturaleza y actualmente se han vuelto tan raras que las tasas de avistamiento son muy bajas. Sin embargo, sus chasquidos de eco-localización pueden ser identificados certeramente con detectores acústicos especializados. Las detecciones acústicas obtenidas en una malla de 46 detectores anclados al fondo indicaron que la actividad acústica de la vaquita declinó en un 80 % entre 2011 y 2015 en la parte central de la distribución de la especie. Dos modelos estadísticos estimaron una tasa anual de declive del 34 % (intervalo de credibilidad bayestano al 95% de-48 % a-21 %). Con base en los resultados del 2011 al 2014, el gobierno de México promulgó, y está haciendo cumplir, una prohibición de emergencia de 2 años para el uso de redes agalleras en toda la distribución de la especie para prevenir su extinción, con un costo de $74 millones de dólares para compensar a los pescadores. El desarrollo de métodos precisos de monitorización acústica resultó ser crítico para exponer la severidad del declive de la vaquita y enf atiza la necesidad de una monitorización continua para manejar efectivamente a especies críticamente amenzadas.

Soybean product utilization in carnivorous fish feeding is limited due to the presence of antinutritional factors (ANFs), which can affect fish growth performance and health status. Probiotic bacteria are commonly used to improve feed utilization in animals unable to digest high levels of protein, carbohydrate, and complex lipids from plant origin. In this study, we evaluated Bacillus sp1, sp3, sp4, and 9b strain probiotic capacity in Totoaba macdonaldi juveniles fed with high levels of soy protein concentrate (SPC). In vitro assays showed that sp1 and sp3 strains were capable of degrading soybean products and other plant-based ingredients commonly used in diet formulation. Soybean meal semi-solid-state-fermentation (SSSF) showed glycinin and β-conglycinin allergenic proteins, and other antinutritional factors were degraded when sp1 and sp3 strains were added to the SSSF process. HPLC product characterization of soybean meal fermented samples with Bacillus strains showed hydrophilic peptide increment and hydrophobic proteins decrement. Diets containing 30% fishmeal substitution with SPC and Bacillus strains sp1, sp3, sp4, and 9b were formulated and used to feed T. macdonaldi juveniles for 8 weeks. Fish growth was carried out using commercial diet (Ct), experimental diet with SPC and without Bacillus (C30), and experimental diets with SPC and Bacillus strains (C30sp1, C30sp3, C30sp4, C309b). Results show that C30sp1 diet produced better weight gain (WG: 224.56 ± 10.79%) than C30sp3 (196.56 ± 11.38%), C30sp4 (177.08 ± 10.79%), and C309b (190.78 ± 13.22%) diets. C30sp1 also produced better weight gain than Ct commercial (123.08 ± 10.98%) and C30 experimental control (194.90 ± 12.33%) diets. Specific growth rate (SGR), thermal growth coefficient (TGC), feed conversion ratio (FCR), and daily feed intake (DFI) parameters were also improved when C30sp1 diet was used. In conclusion, the ability of the Bacillus sp1 strain to degrade soy protein makes it a great feed additive for T. macdonaldi , enhancing growth performance and resulting in larger fish compared to commercially available feeds.

The number of Mexico's endemic porpoise, the vaquita (Phocoena sinus), is collapsing primarily due to bycatch in illegal gillnets set for totoaba (Totoaba macdonaldi), an endangered fish whose swim bladders are exported to China. Previous research estimated that vaquitas declined from about 567 to 245 individuals between 1997 and 2008. Acoustic monitoring between 2011 and 2015 showed a decline of 34%/year. Here, we combine visual line transect and passive acoustic data collected simultaneously in a robust spatial analysis to estimate that only 59 (95% Bayesian Credible Interval [CRI] 22–145) vaquita remained as of autumn 2015, a decrease since 1997 of 92% (95% CRI 80–97%). Risk analysis suggests that if the current, temporary gillnet ban is maintained and effectively enforced, vaquitas could recover to 2008 population levels by 2050. Otherwise, the species is likely to be extinct within a decade.

Finding strategies to use the swim bladder of farmed totoaba (Totoaba macdonaldi) is of the 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. The elemental biochemical composition of totoaba swim bladders, including their proximate and amino acid compositions, was determined. Pepsin-soluble collagen (PSC) was used to extract collagen from swim bladders, and its characteristics were analyzed. Alcalase and papain were used for the preparation of collagen hydrolysates. Swim bladders contained 95% protein, 2.4% fat, and 0.8% ash (on a dry basis). The essential amino acid content was low, but the functional amino acid content was high. The PSC yield was high, at 68% (dry weight). The amino acid composition profile, electrophoretic pattern, and structural integrity analyses of the isolated collagen suggested it is a typical type-I collagen with high purity. The denaturalization temperature was 32.5 °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. The swim bladder from the farmed totoaba could be an ideal source to produce high-quality type I collagen and may be considered an alternative to conventional collagen sources or bioactive peptides.

Recent research evaluating functional ingredients, such as prebiotics, has resulted in a reduction of enteritis caused by some plant ingredients in carnivorous fish. Macroalgae contains polysaccharides that have the characteristics of a prebiotic ingredient. Thus, the objective of this study was to evaluate the effects of macroalgae meal inclusion in formulated Totoaba macdonaldi diets containing soybean meal. Two isoproteic (48%) and isolipidic (13%) diets were formulated to meet totoaba nutritional requirements containing 26% soybean meal, the control diet (SBM-C) without prebiotic and one with the addition of 3% Mega Smart Kelp a macroalgae meal prebiotic (SBM+Pre). In addition, 2 commercial diets formulated with SMB at two levels (7 and 14% labeled ALG1 and ALG2, respectively) and supplemented with the macroalgae meal prebiotic (1.5%) were evaluated. A total of 120 totoabas (157.83 g) were distributed into 450-L tanks in triplicate groups. At the end of the bioassay, the fish fed the SBM-C and SBM+Pre diets had significantly higher growth, better dietary protein efficiency, and higher digestibility compared to fish fed ALG1 and ALG2. Furthermore, a lower expression level of immunoglobulin M ( igm ) and interleukin ( il8 ) genes was observed in the fish fed the prebiotic experimental diets. These results revealed that the commercial diets resulted in lower productive performance of the juveniles and negatively affected the intestinal health of the totoabas, even more than the SBM-C and SBM+Pre diets that included soybean meal and is possibly related to saponin content of these diets.

Two feeding trials were performed to evaluate the apparent digestibility coefficients (ADCs) of dry matter, protein, and amino acids of three animal‐origin and four plant‐origin ingredients in Totoaba macdonaldi. In the first feeding trial, the animal‐origin ingredients were evaluated using totoaba juveniles with an initial weight of 529.7 ± 104.2 g, and for the second feeding trial 745.9 ± 210.6 g. Evaluated ingredients were: poultry by‐product meal, meat and bone meal, feather meal (FM), soy protein concentrate, soybean meal (SBM), corn gluten (CG), and wheat gluten (WG). Each experimental ingredient was evaluated in triplicate. ADCs of dry matter ranged from 35.9% for FM to 67.9% for poultry by‐product, while the protein ADCs values ranged from 41.7% for CG to 83.2% for poultry by‐product. Fish meal ADC (79.6%) was similar to poultry by‐product but significantly higher than WG and soy protein concentrate (72.5% and 72.6%, respectively). The ADCs for lysine were significantly higher for WG, sardine meal, poultry by‐product, and SMB (94.5%, 79.8%, 79.4%, and 79.4%, respectively). Based on the results from the present study, poultry by‐product, WG, and soy protein concentrate are the most promising alternative ingredients (i.e., to the fishmeal) for the formulation of totoaba grow‐out feeds.

In this study, we evaluated the effects of three prebiotics (inulin, β-glucan, and chitosan) on the physiological performance of Totoaba macdonaldi juveniles under culture conditions. The respiratory burst and the leucocyte content were measured in the blood to assess innate immune responses. The intestinal digestive capacity was evaluated by analyzing trypsin, amylase, and lipase activities, whereas the effects of such prebiotics at the transcriptomic level were assessed by implementing the RNA-Seq of liver tissue. After 60 days, fish fed with 0.5% chitosan diets showed the highest respiratory burst, the lowest lipase activity, and the highest number of differentially expressed genes (DEGs), where biological processes related to proteolysis, digestion, and lipid hydroxylation were the most affected. In addition, fish from the chitosan diet showed the highest expression of immunoglobulin genes. In contrast, fish fed with the 1% inulin diet presented the highest diet digestibility and trypsin and lipase activities. These physiological effects align with the highest expression of trypsin-like and chymotrypsin-like genes in the liver of fish from this diet. On the other hand, fish fed the 0.1% β-glucan diets showed the lowest amount of DEGs compared to the control group, most of which were associated with immune response, with an up-regulation of genes related to the complement system and a downregulation of immunoglobulin genes. Based on our results, we propose the inclusion of 1% dietary inulin to improve the digestibility of experimental diets and the addition of 0.5% chitosan to stimulate the immune system of T. macdonaldi juveniles.

High-density culture brings with it chronic stress situations that affect fish welfare. In order to evaluate the effect of tryptophan (Trp) levels on the response to stress, Totoaba macdonaldi juveniles were stocked at low (13.5 kg m−3) and high (27.0 kg m−3) densities (32.5 and 56.4 kg m−3, respectively, at the end of the experiment) in 100-L tanks and fed for 63 days with experimental diets containing different Trp levels: control diet CD0.42 (0.42%) and three supplemented diets with 0.99, 1.55 and 2.19% (0.99Trp, 1.55Trp and 2.19Trp, respectively) (three tanks × density × diet). The high-density stocking fed with CD0.42 diets showed significantly increased blood parameters. Trp decreased catalase (CAT) activity in low- and high-density stocking, while the superoxide dismutase (SOD) activity showed no difference. Serotonin (5-hydroxytryptamine, 5-HT) content decreased, and the serotonin turnover ratio (5-HIAA:5-HT) increased in the brains of fish fed with the CD0.42 diet. Indeed, Trp-supplemented diets helped to restore homeostasis in high-density growth conditions as evaluated by the hematological and plasma parameters as well as the serotonergic activity. When the fish were provided a diet containing moderate Trp levels, plasma cortisol increased under high-density conditions. However, no differences were observed among stock densities when totoaba were fed with the 2.19Trp diet. Notably, survival was unaffected by both Trp or densities, but weight gain (WG) decreased with the dietary Trp levels in the high density culture. In sum, Trp supplementation decreased the parameter values linked to stress response on totoaba juveniles cultured at high stock densities.