The enhancement of abalone stocks: lessons from Japanese case studies

The dramatic declines in abalone Haliotis spp. fishery production have been documented all over the world. Release of hatchery‐reared juveniles into natural habitats has been considered as one measure to sustain and/or augment the current fishery production of abalone, as well as to restore collapsed abalone stocks. However, attempts at abalone release programmes have only been undertaken at experimental scales, except for Japan, where large‐scale stock enhancement programmes for abalone have been undertaken since late 1960s. To evaluate the potential of stock enhancement for abalone, we analysed the release surveys of 13 case studies in Japan in terms of the overall recapture rate (number of recaptures through a lifetime/number of juveniles released), yield per release (YPR, yields from released individuals), the economic efficiency of releases (ratio of income from recaptured abalone to release cost) for each release year, and the contribution of hatchery releases to total catches for each fishing year. The average estimates for overall recapture rates (0.014–0.238) and YPR (3.1–60.3 g/individual) varied between locations and release years. The economic efficiency was estimated at 0.4–6.2. The released abalone contributed 6.9–83.5% to total catches. Hatchery releases could augment total production at some locations, but the success of release programmes would be limited by the carrying capacity at release areas, because density‐dependent mortality occurred following releases in some cases. Throughout Japan, the annual catch of abalone has continuously declined from ～6500 t in 1970 to ～2000 t in the mid‐1990s, despite the increase in the number of hatchery releases. Based on the estimates for YPR, the magnitude of the abalone releases on a national scale has not been sufficiently large to sustain the total production of Japanese abalone, which has primarily fluctuated according to the abundances of wild populations. Our results suggest that releases should be targeted at local populations in regions where stock enhancement is predicted to have the greatest chance of success, and the magnitude of releases should be considered carefully and determined for each region by taking the local carrying capacity into account. We also address the future prospects of abalone stock enhancement.     

Stock enhancement in a commercial mullet,Mugil cephalus L., fishery in Hawaii

Abstract This study showed that cultured striped mullet, Mugil cephalus L., released as juveniles can make a significant contribution to landings in an island commercial fishery. Following pilot hatchery releases from 1990 to 1993, striped mullet fisheries in Kaneohe Bay, Hawaii, USA, were sampled to recover cultured fish from the bay-wide catch. Direct sampling of 181 fishing trips resulted in recovery of 211 cultured striped mullet. By autumn 1994, cultured fish comprised 13.0% (2.8%) of the commercial mullet catch in Kaneohe Bay, and the percentage was increasing logarithmically. This study corroborated predictions from previous studies of juveniles about effects of release strategies on survival of cultured mullet. Following summer releases, recapture rates were strongly affected by fish size-at-release, with a critical release size of 60 mm total length (the smallest size released that was subsequently detected in the fishery). Over 30 000 juveniles stocked in 1990 (but not in a nursery habitat preferred by striped mullet) apparently suffered complete mortality.     

Comparative performance of hatchery-reared and wild Scylla paramamosain (Estampador, 1949) in pond culture

The performance of hatchery‐reared juveniles either in aquaculture grow‐out systems or stock enhancement is likely to be dependent on a range of factors during the hatchery phase of production. With recent progress in the development of hatchery systems for the mud crabs Scylla spp., there is growing interest in evaluation of the quality of hatchery‐reared juveniles relative to wild seed crabs as currently used in aquaculture. Hatchery‐reared and wild‐collected Scylla paramamosain juveniles were stocked either together in ponds or separately. All crabs were tagged with microwire‐coded tags, so that origin could be determined in the mixed groups. Preliminary validation demonstrated that tagging did not affect survival or growth, with a tag retention of 94%. After 106 days of culture, there was no significant difference in survival at harvest between the two sources of crabs. The wild juvenile crabs had a significantly higher initial weight:carapace width (CW) ratio compared with those from the hatchery, indicating a difference in condition. However, where crabs were stocked separately, the hatchery‐reared animals exhibited significantly faster growth than those collected from the wild, both in terms of specific growth rate and CW increase per month. However, in the mixed ponds, where there was competition with wild crabs, there was no significant difference in growth rate between crabs from the two sources. Overall, the results demonstrate that the growth performance of hatchery‐reared S. paramamosain can at least equal that of wild‐collected seed crabs in ponds culture.     

Climate‐induced response of commercially important flatfish species during the 20th century

The consequence of elevated ocean temperatures on commercial fish stocks is addressed using time series of commercial landings (1906–2004) and juvenile survey catch data (1904–2006) collected around Denmark. We analyze (i) whether warm‐water sole (Solea solea) has increased relative to Boreal plaice (Pleuronectes platessa) and (ii) whether two related warm‐water species (turbot, Psetta maxima and brill, Scophthalmus rhombus) show similar responses to increasing temperature or, alternatively, whether turbot (which has a broader juvenile diet) has been favored. Since the early 1980s, both sole and turbot have constituted an increasing part of the commercial landings and survey catches, as compared with plaice and brill, respectively. These changes in species composition were linked to sea surface temperatures, Northern Hemisphere temperature anomalies (NHA) and the North Atlantic Oscillation. NHA was closely related and explained 43% of the observed variation in sole survey catches relative to the plaice catches and almost 38% of the observed variation in the sole landings relative to the plaice landings. For the less common species, turbot and brill, none of the global change indicators explained more than 15% of the variation, although all showed a positive relationship. Survey catch per unit effort increased significantly for both sole and turbot around the early 1980s, whereas catch per unit effort for plaice and brill remained constant. The results indicate that the abundance of warm‐water species is likely to increase with increasing temperature but also that species with similar life histories might react differently according to degree of specialization.     

Experimental nursery culture of the mud crab <Emphasis Type="Italic">Scylla paramamosain</Emphasis> (Estampador) in China

For the improvement of nursery culture of the mud crab Scylla paramamosain, a special nursery facility was purposely designed and built. This facility consists of nursery ponds (areas of 20, 50, and 120 m², respectively) and a seed collecting pond connected to each nursery pond. There were 140 nursery facility units in operation for large-scale juvenile crab production. A series of experiments were carried out using the facility to investigate the effects of the age of megalopae, stocking density, and culture duration of both megalopae and first-stage crabs on the survival of megalopae and early juveniles of S. paramamosain. The results showed that when megalopae were stocked at a density between 3,000 and 5,000 ind m⁻² and reared to reach the first-stage crabs, a survival rate of up to 50% could be achieved. When the first-stage juvenile crabs were stocked at a density between 2,000 and 3,000 ind m⁻², their survival was more than 50% after 14 days of culture.     

THE USE OF HORSESHOE CRABS AS EEL BAIT

Freshly killed male and female horseshoe crabs (Limulus polyphemus) and alewives (Alosa pseudoharengus) were tested as bait for freshwater eels (Anguilla rostrata (Lesueur)) in a Rhode Island estuary. Horseshoe crabs were superior to alewives and the heads of female horseshoe crabs were superior to their tails. Male crabs produced catches between those of the female heads and tails. When divided by the weight of the bait, catch rates of all horseshoe crab baits were similar. Horseshoe crabs might be useful in the commercial culture of eels.     

东海近海蟹笼网目尺寸对三疣梭子蟹的选择性

不断壮大的东海近海笼壶渔业对三疣梭子蟹（Portunus trituberculatus）等甲壳类资源造成了巨大的压力,实施养护幼蟹的管理措施已成为渔业管理者和生产者的共同呼声。本研究通过海上对比试验,分析了放大网目尺寸对蟹笼渔获效率的影响,运用SELECT模型估算了蟹笼对三疣梭子蟹的尺寸选择性,结合混合影响模型探讨了作业时间和可捕群体对选择性分析的影响。结果显示,对照蟹笼（网目尺寸32.0 mm）与试验蟹笼（网目尺寸分别为52.3 mm和59.7 mm）的三疣梭子蟹渔获甲宽分布存在显著性差异;SELECT模型拟合结果显示试验蟹笼与对照蟹笼的相对作业强度无显著性差异,网目尺寸分别为52.3 mm和59.7 mm的试验蟹笼对三疣梭子蟹的50%选择甲宽（CW₅₀）分别为86.9 mm和90.9 mm,选择范围分别为15.9 mm和9.2 mm。试验蟹笼的CW₅₀远未达到浙江省等当前的最小可捕尺寸规定,表明蟹笼渔业中仅依靠放大网目尺寸可能难以实现幼蟹的有效释放。结果分析显示,在此次试验中作业时间和可捕群体的数量对蟹笼的选择性没有显著性影响。     

Pikeperch, Stizostedion lucioperca (L.), catch in relation to juvenile density and water temperature in Pärnu Bay, Estonia

Abstract The abundance of 0+ pikeperch, Stizostedion lucioperca (L.), in trawls was compared with water temperature, water level and commercial catches 6–9 years later. The abundance of juveniles in autumn was positively correlated with the water temperature but not with water level in May or in June. The sum of a year abundance of juveniles showed a strong correlation with the catch years later. This abundance and the cumulative water temperature between August and October inclusive in five consecutive years one year prior to recruitment into the commercial fishery explained 86% of the variation in catches. This empirical model indicates that catches of pikeperch depend on both juvenile abundance and water temperature.     

Size at sexual maturity and body size composition of mud crabs <Emphasis Type="Italic">Scylla</Emphasis> spp. caught in Don Sak,Bandon Bay,Gulf of Thailand

Size at sexual maturity and body size composition of mud crabs Scylla spp. were examined as the basis for settling a minimum landing size as a fishing regulation in Don Sak, Bandon Bay, Gulf of Thailand, which has suffered serious mangrove habitat degradation. Mud crabs were caught using baited traps and gill nets. Hooked metal rods were also used to lever the crabs out of their burrows inside the mangroves. Two mud crab species, S. paramamosain and S. olivacea, occur in the bay; S. paramamosain is the dominant species, accounting for 87% of the samples. The size at which 50% of the S. paramamosain females reached maturity (SM₅₀) was estimated as an external carapace width (ECW) of 112.0 mm based on the morphology of the abdomen. Allometric changes in the crushing chelae height to ECW ratio suggested that the SM₅₀ of S. paramamosain males occurred at 106.4 mm ECW. The body size composition revealed that mainly immature mud crabs were exploited in Don Sak. To maintain a sustainable fishery for mud crabs, fishing regulations—including a minimum landing size based on the SM₅₀ estimates—are essential, as is habitat restoration.     

Effects of co‐supply ratios of swimming crab Portunus trituberculatus zoeae and Artemia on survival and growth of East Asian common octopus Octopus sinensis paralarvae under an upwelling culture system

Despite recent advances in culture technology for East Asian common octopus Octopus sinensis paralarvae using upwelling systems, securing suitable feed for the paralarvae is an unresolved issue. The zoea of the swimming crab Portunus trituberculatus is a good candidate for paralarval feed because of the high fecundity of the adult females. To investigate the effects of supplying P. trituberculatus zoeae and their feeding method on paralarvae, we cultured paralarvae with supplying different combination ratios of zoeae and Artemia (10:0, 7:3, 5:5, 3:7 and 0:10), and with or without supplementing rotifers using small‐scale (3‐L) upwelling systems. Paralarval survival rate and growth were improved when zoeae were supplied as the main feed, but reduced when the proportion of Artemia exceeded half the whole preys. Supplementing rotifers did not affect the paralarval survival and growth. Subsequently, paralarvae were cultured by supplying zoeae (partially augmented by Artemia) using three large (1‐kl) upwelling systems to assess their feeding effectiveness in juvenile octopus production. Paralarvae could be cultured at high survival rates of 77.1 ± 5.1% to reach benthic juveniles at 23 days after hatching. In conclusion, supplying P. trituberculatus zoeae augmented with Artemia under an upwelling culture system has great potential for juvenile octopus production.     

Comparative fishing trials for <Emphasis Type="Italic">Charybdis japonica</Emphasis> using collapsible box-shaped and dome-shaped pots

ABSTRACT:   Comparative fishing trials were undertaken with two commercial collapsible pots for the crab Charybdis japonica . One pot was box-shaped with two slit entrances at the ends, while the other was dome-shaped with two open funnel entrances. Pots were placed at the bottom of a pond that is connected to Kagoshima Bay. Fishing trials were carried out using a 1-day soaking time; the bait used was mackerel. The box-shaped pot had higher catches of crabs and non-target organisms, but the number of large crabs (carapace width >8 cm) was almost half as many as that caught with the dome-shaped pot. The catch of non-target species was also greatly reduced in the dome-shaped pot, and fish caught were mostly enmeshed in the netting. The reduction in catches of small crabs and non-target organisms was due to the nature of the dome-shaped pot's larger mesh size and open entrances, which allowed for escape. The dome-shaped pot seemed more efficient for harvesting commercial size crabs, while the box-shaped pot seemed better for removing all crab sizes.     

A preliminary appraisal of the contribution of recreational fishing to the fisheries sector in north-west Trinidad

Abstract An assessment of the recreational fishery in north-west Trinidad was made by questioning participants about the principal fishing methods used, location of activities, catches, effort and cost of fishing. Surface handline methods (live baiting [à la vive] and trolling) and rod and line (banking) were the most common methods used and were pursued mainly in the summer months (April to August). Total fish landings from the fishery were estimated at 1000 t year^-1, equivalent to about 10% of commercial catches for Trinidad. The principal species caught were kingfish, Scomberomorus cavalla (Cuv.), carite, Scomberomorus brasiliensis (Cuv.), cavalli, Caranx hippos (L.), snappers, Lutjanus spp., and groupers, Epinephelus spp. Many of the fishermen sold their catch to offset the costs of the fishing trip and thus competed with commercial fishermen. Recommendations for monitoring and possibly regulating the fishery through a licensing scheme are made.     

Effect of environmental factors,especially hypoxia and typhoons,on recruitment of the gazami crab <Emphasis Type="Italic">Portunus trituberculatus</Emphasis> in Osaka Bay,Japan

Important crustacean fisheries occur in semi-enclosed seas. These fisheries can be strongly affected by intense exploitation and episodic anthropogenic and climatic events, but the effects of such events remain largely uninvestigated. To assess the influence of such factors, we examined dredge catch data on the gazami crab Portunus trituberculatus in Osaka Bay, Japan from 1984 to 2008 and investigated various associated environmental factors. There were five peak monthly catches during the study period, which typically occurred in August or November. Relative abundance (measured as catch per unit effort) in August was positively associated with previous recruitments to the fishery, typhoon frequency, and dissolved oxygen saturation during the juvenile period. In comparison, relative abundance in November was strongly correlated with the number of typhoons and was also positively associated with dissolved oxygen levels in the bottom water. The results of our multi-decadal study suggest that hypoxia is a principal agent of mortality for juvenile crabs and that normoxia in the nursery habitats is a necessary condition for the successful recruitment of individuals into the adult population. The positive influence of typhoons on recruitment is probably due increased mixing in stratified coastal waters, which disrupts the persistent hypoxia in bottom waters, but other unknown processes may also contribute to favorable recruitments.     

Effect of different forms of Artemia biomass as a food source on survival,molting and growth rate of mud crab (Scylla paramamosain)

An experiment was conducted to evaluate the effect of different forms of Artemia biomass as a food source on survival, molting and growth rate of mud crab Scylla paramamosain. Instar 1 crablets with a mean weight of 0.0082 ± 0.0007 g were reared both individually and communally and fed with different diets consisting of fresh shrimp meat (control feed), live Artemia biomass, frozen Artemia biomass and a dried Artemia‐based formulated feed for 40 days. The highest survival was obtained for crablets receiving live Artemia (92.5% and 75.8%) followed by the groups fed with frozen biomass (90.0% and 47.5%), the control feed (72.5% and 24.2%) and the dried Artemia‐based diet (60.0% and 21.7%) for individual and communal cultures, respectively. The intermolt period, the total number of moltings and the growth rate, which were determined on individually reared crabs, showed the same pattern as for survival. The results suggest that crab performance decreased in the following order: live Artemia>frozen Artemia > fresh shrimp meat > dried Artemia‐based formulated feed. Live Artemia biomass proved an ideal feed for nursery of Scylla paramamosain crabs. Frozen Artemia biomass may be an alternative in times of shortage. Our findings illustrate the high potential for local utilization of Artemia biomass in Vietnam for reliable production of mud crab juveniles.     

The effect of seasonal anomalies of seawater temperature and salinity on the fluctuation in yields of small yellow croaker, Pseudosciaena polyactis , in the Yellow Sea

To include the effects of environmental factors on the production of small yellow croaker, Pseudosciaena polyactis Bleeker, in the Yellow Sea, we applied time series analysis to the commercial catch and salinity and temperature data for the period 1970 to 1988. Residuals from a weighted least-squares regression of log-transformed catches against year and month were calculated to remove not only seasonal factors but also long-term trends in catches. The residuals of mean and standard deviation (SD) of temperature and salinity were calculated and used for autocorrelation, cross-correlation and first-order autoregression analysis (AR(1)) using maximum likelihood. The landings showed a decreasing pattern across years with a conspicuous seasonal cycle within years. Catch residuals showed a strong positive autocorrelation and a conspicuous time-lagged cross-correlation with the residuals of mean and SD of seawater temperature at 75␣m. AR(1) revealed that positive anomalies of mean temperature were associated with positive anomalies in the production of small yellow croaker with a one year time lag. The decrease in the residual of SD of temperature appears to be related to the high production 0.5–1.0 year later. The effect of salinity was negligible compared with that of temperature. Therefore, the warm spawning period and homogeneous temperature condition of previous years for young fish may cause the increase in the following year's yield of this fish species. When used to predict catches in 1989 and 1990, the AR(1) model explained 40% of the variances of the observed landings.     

Discards from the commercial gillnet fishery for dusky flathead, Platycephalus fuscus, in New South Wales, Australia: spatial variability and initial effects of change in minimum legal length of target species

A scientific observer programme was used to quantify the composition and magnitude of discards in the gillnet fishery for dusky flathead, Platycephalus fuscus (Cuvier), in three barrier estuaries in New South Wales, Australia, during the 2001 fishing season. Regulations only permit the retention of legal‐sized dusky flathead and legal‐sized blue swimmer crab, Portunus pelagicus L., and mud crab, Scylla serrata (Forskål); all other organisms were discarded. Sampling was stratified into two time periods; before and after 1 July 2001 which coincided with the increase in the minimum legal length (MLL) of dusky flathead from 33 to 36 cm total length (TL). Eighty one catches were sampled, yielding 38 finfish species and two portunid crab species. Legal‐sized dusky flathead were the most abundant organism captured, accounting for 23–47% by number and 34–54% by weight of the mean observed catch depending on the estuary and survey period, with a mean catch of 25–59 flathead weighing 13–25 kg per fishing‐night. Species composition and relative abundance of catches differed among estuaries, but not between sampling periods. Predominant bycatch species included legal and undersize blue swimmer crab, sea mullet, Mugil cephalus L., luderick, Girella tricuspidata (Quoy & Gaimard), bream, Acanthopagrus australis (Günther) and yellowfin leatherjacket, Meuschenia trachylepis (Günther). These five species accounted for 82% of total bycatch by number and 71% by weight, pooled across the three estuaries. More crabs were retained than discarded, with retained legal‐size crabs (byproduct) accounting for 16% of total bycatch by number and 13% by weight, with an average of 5–22 crabs weighing 1–6 kg being caught per fishing‐night, depending on the estuary. Overall, 7% of dusky flathead captured (number) were below the MLL of 36 cm and discarded, suggesting the nets as currently configured may be relatively selective in catching legal‐size flathead. However, 41% of dusky flathead were <40 cm TL, indicating that if the MLL for this species is increased to this length as proposed, new nets must be introduced into the fishery. The findings are discussed in terms of making the flathead fishery more sustainable, including alternative management strategies for the fishery.     

Fishery biology of mud crabs <Emphasis Type="Italic">Scylla</Emphasis> spp. at Iriomote Island,Japan: species composition,catch, growth and size at sexual maturity

The fishery biology of mud crabs Scylla spp. was examined using baited traps and gill nets from September 2001 to August 2005 at Iriomote Island, Japan. To elucidate the growth of the crabs, artificially produced S. serrata juveniles were released and recaptured at the study site. The sizes at which 50% of females and males of S. serrata reached sexual maturity (SM₅₀) were estimated as an external carapace width (ECW) based on the morphology of the abdomen and the chela respectively. Two species, S. serrata and S. olivacea, were identified in the area with S. serrata being the dominant species (>95% of the catch). Changes in the mean ECW and the results of the release and recapture experiments suggested that the recruitment of young crabs to the fishery occurred from December/January to April/May. The SM₅₀ of females and males occurred at 132.4 and 150.7 mm ECW respectively. The body size composition of S. serrata revealed that immature crabs comprised approximately 40 and 65% of the catch for females and males respectively. To maintain a sustainable fishery for S. serrata, a minimum landing size based on the SM₅₀ estimates should be implemented as a fishing regulation.     

Atmospheric forcing drives recruitment variation in the Dungeness crab (Cancer magister), revisited

For 12 yr (1997–2001, 2006–2012) daily abundance of Cancer magister megalopae was measured in Coos Bay, Oregon. Before 2007 from 2000 to 80 000 megalopae were caught annually. In 2007, catch jumped and has since varied from 164 000 to 2.3 million. The step change in catch size appears related to a shift to negative Pacific Decadal Oscillation (PDO) values. Late season catches, which cannot be due to local spawning, are negatively correlated to the PDO, suggesting that these megalopae derive from north of the California Current. During periods of lower and higher catches, annual returns of megalopae were significantly negatively correlated to the day of the year of the spring transition and positively correlated to the amount of upwelling during the settlement season. The size of the Oregon commercial catch lagged 4 yr to allow for growth of recruits into the fishery is set by the number of returning megalopae; the relationship is parabolic. At lower returns, the population is recruitment limited, but at higher returns, density‐dependent effects predominate and set the commercial catch. Lagged commercial catches in Washington and Northern and Central California were also related to the number of megalopae returning to Coos Bay, suggesting that the forces causing variation in larval success are coast wide. If high return rates are due to a PDO regime shift, then for years to decades the commercial catch may be set by density‐dependent effects following settlement and the huge numbers of returning megalopae may impact benthic community structure.     

Patterns of commercial fish landings in the Loreto region (Peruvian Amazon) between 1984 and 2006

Patterns of commercial fish catches over the period from 1984 to 2006 were studied in the Loreto region and in Iquitos, which is the most important town of the region and the principal fish marketplace of the Peruvian Amazon. Despite important inter-annual variations, the overall fish landings have significantly increased in the region during this period. The same three species dominated the catches during the whole period (Prochilodus nigricans, Potamorhina altamazonica and Psectrogaster amazonica), making up about 62% of the catches. However, the number of species exploited by commercial fisheries increased considerably during the 22 years of this study (from about 21 species in 1984 to over 65 in 2006), although part of the difference may be accounted for by a better identification of individual species nowadays. At the same time, the large high-valued species, such as Arapaima gigas, Colossoma macropomum and Brachyplatystoma rousseauxii, declined significantly and were replaced by smaller, short-lived and lower-valued species. Catches of the silver Arahuana (Osteoglossum bicirrhosum) also declined significantly during the studied period, strengthening recent warnings about the species’ conservation status (Moreau and Coomes, Oryx 40:152–160, 2006). The relative proportions of the trophic groups (detritivores, omnivores and piscivores) remained relatively constant over the study period, but there were significant changes in the relative abundances of the species groups. The proportion of the dominant group, the Characiformes, which averaged about 81% of the catches, increased between 1984 and 2006, whereas the proportion of the Siluriformes and Perciformes remained constant. On the other hand, the proportion of Osteoglossiformes, represented only by two well known species (Arapaima gigas and Osteoglossum bicirrhosum), declined sharply during the same period. Important differences were observed between the landings of Iquitos and the landing of the whole Loreto region, indicating that conclusions drawn from the study of the Iquitos landings cannot be extrapolated to the whole landings of the Loreto region. The most important difference was the decreasing fish landings in Iquitos, whereas the total landings increased in the Loreto region at the same time. Potential causes of this phenomenon are discussed. Decreasing fish abundance around Iquitos (because of a higher fishing pressure) and a behavioural adaptation of fishermen to better law enforcement in Iquitos are likely explanations to be further investigated.     

Climate impacts on the landings of Indian oil sardine over the south‐eastern Arabian Sea

The landings of Indian oil sardine (Sardinella longiceps, Clupeidae) along the south‐eastern Arabian Sea are about 43.8% of total Indian oil sardine production. The annual landings of this species exhibit large‐scale variability with prolonged years of surplus or deficit landings without identified reason. Evaluating Indian oil sardine landings along the Kerala coast during 1961–2017 in relation to environmental variations, we have elucidated a putative link between variability in landings versus environmental parameters and climate indices. The variables examined in this study, such as salinity and temperature along with physical indices such as upwelling and mixed layer depth (MLD) of the ocean help to propose a mechanism to temporal variability in the landings of Indian oil sardine. Colder temperature and timely intense upwelling lead to nutrient enrichment in the surface water, which promotes the growth of phytoplankton (chl‐a) and thereby food availability to Indian oil sardine are found during years with surplus catch. Less saline surface waters and shoaling of MLD at these times could lead to the aggregation of fish at particular depths and thereby a good catches. The reverse mechanism, such as more surface saline water, warm temperature, downwelling or weak upwelling, and less nutrient enrichment, leads to deficit landings. Further, it was noticed that the Pacific decadal oscillation and Atlantic multidecadal oscillation have a more pronounced impact on Indian oil sardine landings over the coast of south‐eastern Arabian Sea than previously reported ENSO associated impacts. All these point towards climate change implications for the Indian oil sardine fishery.