Penaeus vannamei is a penaeid shrimp. Family characteristics include movable chelae (claws) on the first three pairs of walking legs and a third thoracic segment which never overlaps with the second (Williams 1984). The rostrum is moderately long with 7-10 dorsal and 2-4 (occasionally 5-8) ventral teeth. The tip of the rostrum in adults reaches the mid-length of the 2nd rostal segment. The lateral rostral groove ends near the posterior rostral tooth. The post-rostral keel is variable in length, and sometimes almost reaches the posterior edge of the carapace. The antennal spine and hepatic spines are pronounced, and located a short distance apart. The color is similar, but lighter than that of the Atlantic White Shrimp (P. setiferus). Its color is translucent, bluish or olive with dusky bands, reddish-brown on the antennules, but distinguished by white legs (Perez Farfante and Kensley 1997; Perry and Yeager 2006). The last abdominal segment has three lateral scar-like ridges. The maximum length is 220 mm (Food and Agriculture Organization 2011). Synonyms- Since the publication of Perez Farfante and Kensley's (1997) 'Penaeoid and sergestoid shrimps and prawns of the world', this shrimp has been known as Litopenaeus vannamei. That work split the former genus Penaeus into 6 genera. A recent study (Ma et al. 2011) found that the morphological features used to split the genus were not consistent with genetic data. They concluded that the genus Penaeus should be re-unified.
penaeus
Dscam protein forms a horse-shoe shaped structure comprised of the first four extracellular Ig domains, with two surface epitopes, epitope I and epitope II, formed by part of the Ig2 and Ig3 domains. Epitope I is involved in homophilic binding specificity, whereas epitope II is hypothesized to be involved in pathogen recognition21,22. Originally, Dscam was thought to occur only as a membrane-bound form with a transmembrane domain (TM) and a cytoplasmic tail, and although Dscam can be secreted from cells in Drosophila, this can only be achieved by proteolytic activity. Surprisingly, however, it was subsequently found that both shrimp (Litopenaeus vannamei and Penaeus monodon) and crab (Eriocheir sinensis) express a unique tail-less form of Dscam that had neither a transmembrane domain nor cytoplasmic tail10,16,23,24. Type III polyadenylation was thought to provide a mechanism that would generate both membrane-bound Dscam and tail-less Dscam16.
Citation: Nisar U, Zhang H, Navghan M, Zhu Y, Mu Y (2021) Comparative analysis of profitability and resource use efficiency between Penaeus monodon and Litopenaeus vannamei in India. PLoS ONE 16(5): e0250727.
The fisheries sector plays significant role in Indian economy contributing to 0.91% to national GDP and 5.23% to the agricultural GDP [1]. Indian fisheries and aquaculture is an important sector of food production that not only provides livelihood to around 14 million people but also contributes to agricultural exports. Although the shrimp culture has increased during the past decade, the actual potential is still unexploited. The country currently have 176,000 hectares of area under shrimp culture out of which about 91% is under Litopenaeus vannamei production, 8% for Penaeus monodon and only 1% for Macrobrachium Rosenberger [2], Shrimp production can be increased by best utilizing the existing resources through improved practices of shrimp culture [3]. Shrimps are called the pinkish gold of the sea because of its increasing demand, great taste and high unit value realization in the export market. It is one of the immersing industry, which significantly contributes to foreign exchange and trade
The study on Resource use of Litopenaeus vannamei and Penaeus monodon production in Thailand and Vietnam [22], reported that as the production intensity increased, the resources use per metric ton of shrimp reduced. The greater expansion of shrimp ponds with high intensifications leads to lesser use of resources and higher production. The study mentioned the importance of intensification of shrimp farms by stating that in near future to meet the shrimp demands of growing population, the intensification is pivotal. With limited land and water resources, best efficient and productive output can be resulted only by intensification and better management practices.
The clusters earlier identified and studied revealed that the farms of Penaeus monodon were in the yield range of low and medium clusters, while the farms of Litopenaeus vannamei medium, high and very high yielding clusters. With the level of production, the stocking density increased substantially as shown in the Table 3. Yield and feeding rate also increased as the intensity of shrimp production increased. [23] obtained similar results where the yields and feeding intensity increased with the increasing intensification of farms in the Litopenaeus vannamei and Penaeus monodon culture in Thailand and Vietnam respectively. Higher intensity levels were followed by lower culture days. For Penaeus monodon, the medium and low intensity of production were associated with 146 and 158.5 culture days respectively. Similarly for Litopenaeus vannamei, the production clusters of very high, high and medium culture intensities were associated with 127, 141.32 and 154.33 culture days respectively. There was a large variation observed in the stocking densities of both the black tiger shrimp and white legged shrimp. The black tiger was stocked at the rate of 12000 PL per hectare in case of lower intensified to 14000 PL for medium intensified farms. For white legged shrimp, the stocking density varied from 34130 PL/ha for medium intensified farms to 48500 Pl/ha for very high intensity groups.
It is observed that the cost per kilogram per hectare of shrimps produced decreased with the increase in the production intensity (Table 6). For Penaeus monodon, the cost per kilogram per hectare was US$ 4.28 for low intensity level, and later reduced to US$ 3.82 for medium intensity level. Similar pattern was observed for Litopenaeus vannamei, the costs decreased from US$ 4.03 for medium intensity to US$ 3.64 for very high intensity of production. The production process of the shrimps followed the economies of scale by sparing in costs and by expanding the culture. Net returns per hectare increased by increasing the level of intensification. As the production increased across the levels of intensification, more volume of output produced resulted in greater gross recipients. For Penaeus monodon, the net returns for the lower intensity are $12280.63 and for medium intensity $20345.63 implying the enterprise as a profitable venture. White legged shrimp matures in short duration of time and in that case the culture is done twice a year making the net returns to $29793.98, $36207.00 and $58921.98 for medium, high and very high intensities respectively as shown in Fig 2.
Resource-use efficiency was estimated for those variables that had significant effect on shrimp production of both the species. It is observed that the efficiency ratio [Marginal Value Product (MVP) to Marginal Factor Cost (MFC)] for Penaeus monodon (black tiger shrimp) is greater than unity for feed indicating its under-utilized (Table 9). In the production of Litopenaeus vannamei (white legged shrimp), efficiency ratio is greater than unity for use of seed indicating it is underutilized and for labor the ratio is less than unity (over-utilized). Greater than unity values for efficiency ratio in seed and less than unity value for labor exhibits that the output was likely to increase and hence revenue, if more of seed and less of labor would have been used in the shrimp production. In the previous section, the production elasticity of labor has suggested that increase in use of labor will increase shrimp production, however, this increase will not add to the profit of shrimp farmers.
To achieve the most efficient input-use, the value of the marginal value product (MVP) should be equal to its marginal factor cost (MFC) or price [43]. If the MVP of an input is greater than its price, then the profitability can be increased by increasing the level of that input. On the other hand, if the MVP of an input is less than its price then profit can be increased by decreasing that input. In the first regression model of shrimp production (P. monodon) as shown in Table 9, feed (Fd) was statistically significant and this input should be increased, since its MVP is greater than MFC. In the second regression model of shrimp production (Litopenaeus vannamei), in order to improve the profitability, seed (Sd) should be increased since its MVP is greater than its MFC, whereas the use of labor should be decreased as its MVP is lesser than its MFC.
The study reveals that as the level of intensification increased across the clusters, the profitability also increased. The level of intensification in each cluster increased the profit margins and reduced per unit costs of production by attaining the economy of scale. [45] in his study of intensification of catfish production revealed that with increase in production, the profitability increased with reduction in per unit costs. [46] carried out similar study where the results obtained were contrasting and per unit costs increased with the increase in the production systems. Quite often, the crop failures are blamed on post larvae quality, feed, disease outbreak, and water quality but most often the origin of the failure is poor feed management [47, 48]. So in order to increase the profitability, the farmer should shift from one level to another level of intensification. However, the farmers need more experience, management skills and capital to shift. In addition to this, the farmers should also possess the risk taking ability, as the shrimp culture is more uncertain for disease outbreak and mortality. The long run profitability of the shrimp farmers in India is affected by the increasing prices of medicines, the cost of hired labors and diseases like WSSV (White Spot Syndrome Virus) which are more prone to Litopenaeus vannamei. Land values and construction costs greatly increases the fixed costs, which ultimately hinders the profitability. It is observed that per unit cost of production is affected greatly by the yield but the yield itself is dependent upon the stocking densities, feeding rate, culture days, aeration rate and others. Therefore, yield can be different for same stocking densities per hectare depending on the level and intensities of the other management practices and inputs used. 2ff7e9595c
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