Satellite based potential fishing zone (PFZ) advisories - acceptance levels and benefits derived by the user community along the Kerala coast

Intensive validation studies of potential fishing zone (PFZ) advisories generated using integration of ocean colour monitor (OCM) derived chlorophyll concentration and advanced very high resolution radiometer (AVHRR) derived sea surface temperatures (SST) were undertaken by the Indian National Centre for Ocean Information Services (INCOIS) along Kerala coast during the period 2003-2011. There is a positive relationship between PFZ advisories and occurrence/abundance of commercially important pelagic fishes such as oilsardine, Indian mackerel, anchovies, carangids and coastal tunas. Fishing operations undertaken on or closer to dates on which related SST/chlorophyll images have been received yielded positive results. As the gap increases, the yield within PFZ is likely to come down unless the features remain more or less in the same location as revealed by succeeding satellite imagery. The present paper revealed that the fish catch (CPUE) and net profit earned are higher within PFZ compared to the results of operations outside PFZ. The usefulness of PFZ advisories, the only short term marine fishery forecast available in the country for fisherfolk towards obtaining comparatively higher catch per unit effort for the above mentioned major pelagics is proved beyond doubt from the results of more than 100 controlled experiments conducted within and outside PFZ with identical fishing gear along Kerala coast

Studies on major small pelagic fishes along the Kerala Coast with respect to the Potential Fishery Zone (PFZ) advisories

Indian National Centre for Ocean Information Services (INCOIS), Hyderabad, India provides fishery forecast services all along the Indian coast free of cost, referred to as ‘Potential Fishery Zone (PFZ) Advisories’. These services include georeferenced maps showing marked regions where probability of finding sizeable schools of fishes is high. These advisories are provided to help the fisher folks to improve their income from fishing by saving engine fuel for searching and locating fish stocks. Based on 124 controlled fishing experiments carried out in the PFZ and Non-PFZ zones along the Kerala coast during 2008-2012 periods, the present study evidenced that commercially important fishes were abundant in the PFZ, forming richer fisheries compared to the non-PFZ areas. The profit from controlled experiments showed consistently higher values in the PFZ than that in the non-PFZ. The highest profit during the entire controlled fishing experiments was obtained when the catch was dominated by relatively high-priced fishes such as tunas, carangids, seer fishes and mackerel. Indian oil sardine was the major single species obtained during the Northeast Monsoon (November-February), whereas, Indian mackerel dominated during the Southwest Monsoon (June-October) and Spring Intermonsoon (March – May) periods. Anchovies were found to dominate only in two fishing experiments in the entire study period. The analyses of catch data of the small pelagic fishes of interest (Indian oil sardine, Indian mackerel and Commerson’s anchovy) showed that the PFZ advisories better predicted the catches of Indian oil sardine during the Northeast Monsoon (November- February) and Indian mackerel during the rest of the period. Conversely, the catch data of controlled experiments showed that PFZ advisory has less efficiency to support the exploitation of anchovies. Attempts have been made to outline the recurrent PFZ along the Kerala coast based on the advisories generated for the study period (2008-2012). Altogether 432 PFZ advisories were digitised and month-wise repeat PFZs have been demarcated. In general, most of the very prominent recurrent PFZs were found within the 50m depth contour. The highest number of recurrent PFZs was in December, January and February. On the other hand, the lowest number of recurrent PFZs was found in April, May and June. Plankton components in the diet of Indian oil sardine, Indian mackerel and Commerson’s anchovy based on fortnightly fish samples analysed during a year period are presented. Coscinodiscus, Nitzschia, Pleurosigma and Thalassiosira were found in the gut of Indian oil sardine almost throughout the year, whereas microzooplankton was mostly dominant only during the October – December period. Coscinodiscus and Tintinids were predominant in the gut of Indian mackerel throughout the year. Furthermore, Thalassiosira, Ceratium, Dinophysis, Protoperidinium, Pyrophacus and copepods were also found in the gut of Indian mackerel almost throughout the year. The dominant value index showed the dominance of phytoplankton, microzooplankton and copepods in the diet of Indian mackerel throughout the year, indicating their almost equal preference for both phytoplankton and zooplankton. The food items in the gut content of Commerson’s anchovy showed characteristic difference from both Indian oil sardine and Indian mackerel and found to be a zooplankton feeder predominantly feeding on copepods, fish eggs, ostracods, lucifers and tintinids. The environmental observations based on monthly field sampling carried out in two locations (10m and 20m depth contours) situated off Kochi are presented. During seven out of nine observations, PFZ bands were observed around 10m location. High values of chlorophyll (> 3mg m-3) were found in August, September and October, which could be attributed to the combined effect of Cochin backwater influx and upwelling. The seasonal evolution of hydrographical parameters showed significantly higher concentration of nutrients and chlorophyll during the Southwest Monsoon period compared to the rest of the sampling. The chlorophyll concentration was found to be significantly higher in 10m location (PFZ) compared to the 20m location (non-PFZ). The status of the Length-Weight Relationship (LWR) and condition factor of Indian oil sardine, Indian mackerel and Commerson’s anchovy along the Kerala coast is presented. The LWR of Commerson’s anchovy is the very first detailed report from this region. LWR and condition factor of Indian mackerel and Oil sardine were not significantly different from the values reported in the historical studies, indicating that these parameters are not affected significantly by the expected long-term environmental changes. The results of the growth and maturity studies of the small pelagic fishes of interest have been discussed. The analyses were based on a fortnightly sampling carried out in two major landing centres during 2010 – 2011 periods. The maximum life span of Indian oil sardine was estimated to be 2.63 years. Two peaks of recruitment of juveniles to the fishery were observed; a large peak during July - August and a small peak in February - March. The length at first maturity was calculated as 15.7 cm while the length at first capture was 15 cm, suggesting that the peak exploitation of the species occurs before they attain sexual maturity. Comparison of the length at first maturity of oil sardine reported in historical studies with the present study shows that only minor variation exists between the two. The life span of Indian mackerel is estimated to be 2 years. The recruitment pattern showed the presence of mature mackerel all year round. However, two recruitment peaks of Indian mackerel were evident; June to August and February to March with the highest recruitment in July (28%). Probability of capture of mackerel showed higher values (22.43 cm) than the length at first maturity (17.7 cm) indicating that their peak exploitation occurs after attaining sexual maturity. Long-term changes in length at first maturity of Indian mackerel indicated a prominent decrease in length in the recent decade, probably indicating a response to the long-term environmental changes. The present study on the growth and maturity parameters of Commerson’s anchovy forms the first such study from Indian waters and the life span of the species was found to be 3.06 years. Two recruitment peaks of Commerson’s anchovy were observed; first during February – March and a second during June - July. The probability of capture of Commerson’s anchovy showed that they get exposed to maximum exploitation after they attain maturity. Lack of past data on length at first maturity of Commerson’s anchovy from the Indian coast hindered a possible comparison with the present data

Length-weight relationship and relative condition factor of Stolephorus commersonii (Lacepede, 1803) exploited along Kerala coast

The length-weight relationship and relative condition factor of Stolephorus commersonii was calculated to assess the significance of allometric factor and the well being. The study was carried out by using the data collected from ring seine and purse seine catches during the year 2010-2011. The length of species in catches ranged from 5 to 14.6 cm with a mean length of 9.24 ± 1.83 cm and the weight ranged from 1 to 25g with an average weight of 6.64 ± 3.96 g. Length-weight relationship calculated for male, female and pooled are W = 0.0070 L3.02, W = 0. 00756 L2.99 and W = 0. 0073 L3.006 respectively. The relative condition factor (Kn) estimated separately for male and female showed monthly fluctuation. The highest Kn values were observed in February and August and the lowest in June for both the sexes

Potential fishing zone (PFZ) advisories-Are they beneficial to the coastal fisherfolk? A case study along Kerala coast, South India

Intensive validation of Potential Fishing Zone (PFZ)advisories generated by the Indian National Centre for Ocean Information services(INCOIS) along the Kerala coast during the period 2006-2010 revealed a positive relationship between PFZ and occurrence/abundance of commercially important pelagic fishes. The usefulness of PFZ advisories for artisanal, motorized and small mechanized sector fishermen towards obtaining comparatively higher catch per unit effort for the major pelagics and thereby improving the economics of fishing operations is highlighted. Analysis of catch data from active fisherfolk and controlled experiments undertaken within and outside notified areas simultaneously showed that catch per unit effort (CPUE) was more in notified areas compared to un notified areas. The extra quantity of fish caught in notified areas is about 2 to 6 times The percentage of extra monetary benefit obtained in notified areas is about 2 to 7 times

Growth and maturity of Indian oil sardine Sardinella longiceps (Valenciennes, 1847) along southwest coast of India

Growth studies are important to determine the total recruitment of fish with respect to time while information on age and length at first maturity are essential to assess the spawning stock. The present communication deals with growth, maturity and mortality parameters of Indian oil sardine Sardinella longiceps from southwest coast of India. Length at first maturity of oil sardine was found to be 15.7 and 15.2 cm for male and female, respectively. Comparison of length at first maturity of oil sardine with earlier studies showed only minor variations. The growth parameters L∞, K, and age at zero length (t0) were calculated as 19.8 cm, 1.14 yr-1 and -0.0464 respectively. From the VBG equation, the length attained at the end of I, II and III year is estimated as 13.79, 17.87 and 18.9 cm respectively. Two peaks of recruitment to the fishery were observed. The values of total mortality (Z), natural mortality (M) and fishing mortality (F) estimated are 4.33, 2.7 and 1.6 respectively. The exploitation rate was found to be 0.37

Seasonal variations in the diet of the Indian oilsardine, Sardinella longiceps Valenciennes off Cochin, Kerala

Seasonal fluctuations in the food of the oilsardine Sardinella longiceps landed by ring seines from the inshore waters off Cochin were studied during 2010. S. longiceps is chiefly a plankton feeder with diatoms, dinoflagellates and zooplankton appearing in the diet in decreasing order of abundance. During pre-monsoon (February-May), Pleurosigma was present in 70% of the stomachs analysed followed by Thalassiosira, Biddulphia and Coscinodiscus. During monsoon season (June-September), 87.5% of the stomachs contained Coscinodiscus followed by Thalassiosira and Pyrophacus. During post-monsoon (October- January) again, the frequency of occurrence of Pleurosigma (74.2%) was higher followed by Biddulphia and Thalassiosira. Zooplankton, represented by tintinnids and copepods, were present in the diet throughout the year, but in relatively less number of stomachs. Higher feeding activity was observed during monsoon (June-September), which coincided with maximum spawning activity

Validation of tuna Potential Fishing Zone advisories of Lakshadweep with a note on tuna habitat preferences and biology

Validation of tuna Potential Fishing Zone advisories of Lakshadweep with a note on tuna habitat preferences and biolog

Stock structure analysis of Indian mackerel Rastrelliger kanagurta (Cuvier, 1817) from south-east and south-west coasts of India using truss network system

A total of 200 specimens of Indian mackerel (Rastrelliger kanagurta) were collected from Kochi in the south-west coast and Chennai in the south-east coast and they were subjected to truss analysis. A truss network was constructed by interconnecting 10 landmarks to form a total of 21 truss distance variables extracted from the landmarks. The transformed truss measurements were subjected to factor analysis which revealed that there is no separation of the stocks along south-east and south-west coasts. Thus the present study has indicated that the population of Indian mackerel from south-east and south-west coasts remains the same

Two instances of gonadal abnormalities in Indian mackerel

The Indian mackerel Rastrelliger kanagurta is known to be dioecious with male and female gonads in separate individuals. However, gonadal abnormalities such as hermaphroditism and other aberrations have been observed in a few instances. Gonadal abnormalities in mackerel observed during regular biological sampling from fish samples collected from the landing centre is reported here. For the histological analysis, the gonads were fixed in 10% neutral buffered formalin, dehydrated in ethanol series and the cleared samples were embedded in paraffin wax and made into blocks

Stock structure analysis of oil sardine Sardinella longiceps (Valenciennes, 1847) from southeast and southwest coasts of India

A total of 200 specimens of oil sardine Sardinella longiceps collected from Kochi in the southwest coast and Chennai in the southeast coast were subjected to truss analysis. A truss network was constructed by interconnecting 10 landmarks to form a total of 21 truss distance variables extracted from the landmarks. The transformed truss measurements were subjected to factor analysis which revealed that there is no separation of the stocks along southeast and southwest coasts. The marginal differences in shape and form are attributed to the ecological differences in the habitats which is evident from differences in length weight relationships and feeding intensity of the population along these two coasts