Exploitation Rate Research Articles

Stock assessment of rosy barb, Pethia conchonius (Hamilton, 1822) in Dal Lake of Kashmir Himalayas

For management of fish stocks, assessing the various parameters of population dynamics are regarded as being extremely important. Under this backdrop the population dynamics parameters viz. growth, mortality and recruitment of Pethia conchonius, inhabiting the Dal Lake of Kashmir Himalayas were analysed using FiSAT II software. The analysed specimens were collected from five different sites within the lake and exhibited a total weight range of 0.3 to 6.4 g and a total length range of 3.1 to 7.8 cm. The relative condition factor for the fish was reported to be 1.11. The growth parameter i.e., asymptotic length, age at zero length, growth performance index and growth constant were reported to be 10.0 cm, –0.75 years, 1.48 and 0.30 year–1 respectively. The total mortality of 1.49 year–1, consisting of natural mortality of 0.88 year–1 and fishing mortality of 0.61 year–1 was reported. An exploitation rate of 0.41 is suggestive of a less exploited state of the fish. The length at first maturity was found to be higher than the length at first capture, a condition that can disturb the stock, as such the utility of a net with relatively larger mesh size is advisable. The current research on the population dynamics of P. conchonius can be used as the baseline data for its management practices.

Sustainable aquaculture of West African freshwater prawns Macrobrachium vollenhovenii (Herklots, 1857) and M. macrobrachion (Herklots, 1851) (Decapoda: Caridea: Palaemonidae)

Abstract The river prawn Macrobrachium vollenhovenii (Herklots, 1857) and the brackish river prawn M. macrobrachion (Herklots, 1851) are economically and ecologically significant West African species. Recent molecular studies suggest they might be different ecotypes of the same species, complicating taxonomy and sustainable aquaculture practices. Both species face significant threats from human exploitation, leading to high exploitation rates and smaller average sizes within populations. Seasonal variations affect their abundance, with M. macrobrachion more prevalent during the rainy season and M. vollenhovenii thriving in the dry season. Their omnivorous detritivorous feeding habits involve consuming detritus, diatoms, phytoplankton, and insect larvae during juvenile stages. Aquaculture of M. vollenhovenii and M. macrobrachion encounters difficulties such as limited hatchery technology and low larval survival rates. Efforts to cultivate juveniles or adults in captivity face obstacles like high mortality rates due to moulting stress, handling, feeding, and cannibalism. Reintroducing captive-bred prawns into the wild offers dual benefits: controlling snail populations that host parasite causing schistosomiasis and restoring ecological balance while enhancing local fisheries and providing socio-economic benefits. To achieve sustainable aquaculture, it is crucial to address taxonomic complexities, implement management measures to mitigate overexploitation, improve hatchery technology, optimise feeding strategies, reduce stress during moulting and handling, and engage local communities through capacity building and awareness programs. This review aims to contribute to a better understanding of these prawns, promoting informed decision-making for sustainable management, conservation, and socio-economic benefits in West Africa.

Population Dynamics and Stock Status of the Round Sardinella (Sardinella aurita, Valenciennes, 1847) in the Coastal Waters of Côte d’Ivoire (West Africa)

This work was carried out to fill for a short time the lack of available data on the dynamic of Sardinella aurita within Côte d’Ivoire’s coastal waters. A total of 2000 samples of S. aurita were collected from May 2022 to April 2023, measured for total lengths and examined using FiSAT II. The asymptotic length (L∞) and growth rate (K) were 31.50 cm and 0.78 year-1 respectively implying that this species is a fast-growing and a shot live species. The lengths at first maturity and first capture were estimated at 18.49 cm and 23.42 cm respectively. The natural mortality rate (M=1.49 year-1) was higher than the fishing mortality rate (F=0.61year-1). The recruitment trend was continuous throughout the year with two major peaks showing the presence of strong recruitment into the stock. However, the exploitation rate (E=0.29) was lower than the 0.5. Furthermore, using the Quadrant rule, the investigated stock was categorized as underexploited. However, the current exploitation rate is higher than E0.5 inviting us to be more careful and to take appropriate measures.

Growth, mortality, and exploitation rates of the mantis shrimp Erugosquilla massavensis (Kossman, 1880) (Malacostraca: Stomatopoda) in Iskenderun Bay, north-eastern Mediterranean of Türkiye

ABSTRACT Lessepsian Erugosquilla massavensis is one of the three Stomatopod species reported on the Levantine coast of Türkiye. Its natural habitat is the Red Sea and it is the first Red Sea stomatopod species reported from the Mediterranean. This study aims to determine the morphometric relationships, growth parameters, sex ratio, age, mortality, and exploitation rates of non-native E. massavensis in the north-eastern Mediterranean. Samples were collected monthly by commercial trawl surveys between September 2016 and March 2017 in Iskenderun Bay. Relationships between the carapace length (CL)–total length (TL) and the total length (TL)–total weight (TW) were estimated. Negative allometric growth was observed between the CL–TL and TL–TW relationship for females, males, and all. The von Bertalanffy growth parameters (vBGP) were found L ∞ = 155.4 mm, K = 0.520 year−1, t 0 = −0.199, ø′ = 4.099 for females, L ∞ = 157.5 mm, K = 0.600 year−1, t 0 = −0.127, ø′ = 4.173 for males. This research provided the first-ever data on the vBGP of E. massavensis. The study found that both sexes had a higher fisheries mortality coefficient than natural mortality (Z = 2.01, M = 0.71, F = 1.3) and were exploited (E = 0.65).

Growth and Mortality Models of Mozambique Tilapia (Oreochromis mossambicus; Peters, 1852) Wildly Enter Inside the Fish Farming Ponds in Tarakan City, North Kalimantan

Graphical Abstract Highlight Research The results of this research showed that allometric growth in males and females had negative allometric growth characteristics. The growth condition index in male and female fish is dominated by thin and fat body shapes.The maximum length growth (L∞) and growth speed of males is higher than that of females. Total mortality and fishing mortality for males is higher than for females, but natural mortality for females is higher than for males. The exploitation rate of males and females is in the Under-exploitation category because the E value is <0.5. Abstract Exploring the length-weight relationship of fish and characterising growth parameters is essential in fisheries as they offer fundamental biology and population dynamics data to establish good management strategies for fisheries resources. This study examines the growth and mortality patterns of Oreochromis mossambicus. Data was collected between September and December 2022 using quantitative descriptive survey sampling. The study involved 20 repeats and deliberate random sampling of 30-50 fish per sample, emphasising total length, weight, and sex parameters. Based on 726 samples of O. mossambicus (352 fish identified as male and 374 fish identified as female). The growth model study revealed the typical negative allometric growth for both sexes (male and female). Male individuals attained a length of 33.449 cm after 37 days has a growth trend ± 0.3265 year-1, and females reached 21.150 cm in 34 days with a growth rate around 0.3135 year-1, as per the von Bertalanffy growth model. There were complex mortality patterns, with males contributing to most total deaths. This study emphasises the complex biology of tilapia and its untapped potential in the aquaculture pond system ecology in Tarakan.

Enabling Creative Destruction: A View from the Perspective of Managerial Control

Creative destruction originates in successful development and launch of a radically different product/process/market configuration, or radical innovation, by a company. A radical innovation can materialize in a business firm only if autonomy is extended to organizational personnel, towards experimentation with heterogeneous knowledge from outside the organization. In this article, I inquire into conditions that enable the materialization of radical innovation—an important precursor to creative destruction—while affording top management the wherewithal to stay in control. An extended version of March’s computational model suggests that when a radical innovation project initiates with a low level of collective human capital with respect to the new process–product–market domain being considered and the project personnel are provided a certain extent of autonomy to experiment in the new domain, top management can detect a change to organizational outcomes by changing the rate of exploitation. Thereby top management obtains a feeling of being in control of proceedings. This situation is, therefore, conducive to the materialization of creative destruction. The indirect method of control to nurture radical innovation—demonstrated in this research—constitutes an improvement over the autonomy-averse ‘agency’ and ‘transaction cost economics’ approaches that are sub-optimal in open systems characterizing radical innovation efforts in corporate venturing.

Population structure and exploitation rate of striped snakehead (Channa striata) in Kawunganten Swamp, Cilacap, Indonesia: Important for fisheries management

Abstract. Setyaningrum N, Sugiharto, Susatyo P. 2024. Population structure and exploitation rate of striped snakehead (Channa striata) in Kawunganten Swamp, Cilacap, Indonesia: Important for fisheries management. Biodiversitas 25: 3255-3263. Snakehead (Channa striata) is a swamp fish spread in almost all Indonesian waters and has a high economic value. In addition, Bringkeng, Grugu, and Babakan Villages are included in Kawunganten Swamp areas with good fishing potential. Therefore, this study aimed to determine the population structure and the exploitation rate of Channa striata in Kawunganten Swamp Cilacap, Indonesia. The survey method with purposive random sampling was used and this study was conducted from April to July 2020. The fish samples were collected from three Bringkeng, Grugu, and Babakan Swamp stations, while the variables examined were abundance and rate of exploitation. The parameters measured included the length of Channa striata as well as the growth and mortality rate in each swamp. Abundance was analyzed using the Kruskal-Wallis test, and exploitation rate was assessed with Pauly's model using FAO-ICLARM Stock Assessment Tools II (FISAT II). The results showed that the highest abundance of Channa striata was in Bringkeng station, three times higher than in Babakan station. Bringkeng and Babakan stations were considered a fish-rearing swamp due to the dominance of adolescence-sized samples. Grugu was identified as the breeding area because many of the fish present were in the reproductive phase. Estimated growth parameters showed a maximum length (L?) of 35.18 cm, while exploitation rate of 0.28 was not considered excessive capture. Efforts to manage Channa striata were important to preserving biodiversity and ensuring the sustainability of Kawunganten Swamp ecosystem for future generations.

Legacy soil phosphorus bioavailability in tropical and temperate soils: Implications for sustainable crop production

Improving phosphorus (P) use efficiency is key to improving the productivity and sustainability of cropping systems and slowing the exploitation rate of mineral P resources required for fertilizer production. At present, large amounts of added P in fertilizers and manure each year are retained in the soil and are not used by the crop. This ‘legacy P’ progressively accumulates in soil and represents an untapped P resource in tropical soils while in temperate soils it contributes to eutrophication. In the context of legacy P, the aim of this study was to quantify changes in soil P pools of contrasting bioavailability (determined using conventional chemical extraction procedures) during 12 successive brachiaria (Urochloa ruziziensis) cropping cycles in which no additional P was added. The study was undertaken in the greenhouse with 10 tropical (Brazil) and 6 temperate (UK) agricultural topsoils. Above-ground dry matter yield (DM) and P offtake was measured at each harvest alongside operationally-defined measures of the labile, moderately-labile and non-labile P pools at the start and end of the experiment. Over twelve repeated cultivation cycles, brachiaria demonstrated an ability to efficiently mine legacy P from all measurable soil pools across both sets of soils. This included the depletion of up to 87 % of non-labile soil P in some soils from the UK and up to 66 % from soils in Brazil after one year. While the amounts of initial labile P showed the closest positive relationship with plant P export, contrary to expectation the non-labile P pool also clearly contributed to plant nutrition across all the soils. As a cover crop, brachiaria clearly possesses traits which enable both the solubilization and efficient capture of soil P that can be harnessed to actively recycle historically non recalcitrant soil P fractions. Incorporating brachiaria into crop rotations or intercropping systems therefore shows promise as a strategy to enhance the longer-term sustainability of soil P management.

A note on the two approaches to the distribution of surplus value

Abstract In a recent issue of this Journal, Cogliano (in ‘Marx’s equalized rate of exploitation’, Cambridge Journal of Economics, 2023, vol. 47, no. 1, 133–69) provided a theoretical basis of the hypothesis that the rates of exploitation are uniform across industries. In this paper, we compare the hypothesis and an alternative approach that assumes that the value creation per unit concrete labour is uniform. As neither approach considers skill differentials, we provide an extended framework that incorporates skills explicitly for the comparison. In addition, our framework considers the value creation of workers as a function of their skills and efforts of labour and, following Yoshihara (in ‘Wealth, exploitation and labor discipline in the contemporary capitalist economy’, Metroeconomica, 1998, vol. 49, no.1, 23–61), we define the ratio between effort and wage as labour discipline. Within this framework, we show the following. The equalisation of the rates of exploitation is eventually assuming that the ratios between the value creation and wage are equalised and it implies that high-skilled workers experience proportionately weaker labour discipline whereas low-skilled workers experience stronger labour discipline. On the other hand, the alternative approach that assumes the equalisation of the value creation per unit concrete labour implies that high-skilled workers work proportionately less intensively whereas low-skilled workers work proportionately more intensively.

Preliminary Prevalence Estimates of Sexual Exploitation as Measured by the Sexual Experiences Survey-Victimization (SES-V) in a National US Sample

ABSTRACT The new Sexual Experiences Survey-Victimization (SES-V) was designed to capture a larger range of sexual exploitation and to be applicable to more diverse populations than prior measures. This study represents the first administration of the SES-V in a national sample of adults (N = 347). Participants were recruited from a crowdsourcing platform and selected to reflect the national distribution in terms of age, sex, and race/ethnicity. Rates of sexual exploitation since age 14 were very high in this sample (90%), providing evidence that the SES-V was successful in capturing experiences on the low end of the severity continuum. Using the items corresponding to the FBI definition of rape, 60% of women and 29% of men endorsed rape on the SES-V. Compared to men, women reported higher rates of sexual exploitation overall, and higher rates of every type of sexual exploitation except technology-facilitated. The new SES-V also asks participants to estimate the number of separate instances of four types of sexual exploitation that they have experienced; results provided support for the value of these incident estimates in understanding the scope of sexual exploitation. Finally, this study evaluated new sexual acts and exploitative tactics that were added to the SES-V and found that they demonstrated utility and validity. These findings offer preliminary support for the validity and functionality of the SES-V, although the high prevalence of sexual exploitation on the SES-V is discussed as both a strength and limitation. Future research should evaluate prevalence and demographic differences in a larger national sample.

Preliminary Evidence of Validity for the Verbally Pressured and Illegal Sexual Exploitation Modules of the Sexual Experiences Survey-Victimization

ABSTRACT The Sexual Experiences Survey-Victimization (SES-V; see Koss et al., 2024) revises the prior 2007 Sexual Experiences Survey-Short Form Victimization (SES-SFV) in many ways, including expanded measurement of verbally pressured and illegal sexual exploitation, as well as the addition of items that assess being made to perform a sexual act or to penetrate another person sexually. The current article describes two initial validity studies of the SES-V. Study 1 compared rates of self-reported verbal pressure and illegal sexual exploitation (e.g. rape) on a preliminary version of the SES-V and the SES-SFV in a sample of higher education students who completed both questionnaires online in a randomized order (N = 460). As expected, the preliminary SES-V produced higher rates than the SES-SFV, and continuous scores were strongly correlated. Responses to the made-to-penetrate (MTP) items suggested that some cisgender men and women may have misunderstood those items. Study 2 explored responses to the MTP items further by randomly assigning participants to complete items with either the Study 1 MTP language (n = 269) or revised language (n = 245). The revised language produced fewer implausible responses and was adopted in the final version of the SES-V. These findings provide initial support for the validity of the SES-V and the value of expanding the conceptualization of victimization to include a wider range of sexual exploitation. A research agenda for future validity research is suggested.

Lessons from the Teca Ho/New Voices Project on Best Practices for Interviewing Native Youth Survivors of Sex Trafficking

Although there are high rates of commercial sexual exploitation of Native American children, there are still not established best practices for interviewing them about their experiences. This pilot study sought to learn more about best practices for interviewing Native including gender diverse youth in the United States about sex trafficking. In the process, lessons were learned about conducting this kind of research. The initial practices suggested included ways of linking with participants, incorporating culturally-specific healing elements, orienting clinicians to cultural humility and agility, and preparing to provide a clear rationale for how and why the information learned would be disseminated.

Extinction Chains Reveal Intermediate Phases Between the Safety and Collapse in Mutualistic Ecosystems

Ecosystems are undergoing unprecedented persistent deterioration due to unsustainable anthropogenic human activities, such as overfishing and deforestation, and the effects of such damage on ecological stability are uncertain. Despite recent advances in experimental and theoretical studies on regime shifts and tipping points, theoretical tools for understanding the extinction chain, which is the sequence of species extinctions resulting from overexploitation, are still lacking, especially for large-scale nonlinear networked systems. In this study, we developed a mathematical tool to predict regime shifts and extinction chains in ecosystems under multiple exploitation situations and verified it in 26 real-world mutualistic networks of various sizes and densities. We discovered five phases during the exploitation process: safe, partial extinction, bistable, tristable, and collapse, which enabled the optimal design of restoration strategies for degraded or collapsed systems. We validated our approach using a 20-year dataset from an eelgrass restoration project. Counterintuitively, we also found a specific region in the diagram spanning exploitation rates and competition intensities, where exploiting more species helps increase biodiversity. Our computational tool provides insights into harvesting, fishing, exploitation, or deforestation plans while conserving or restoring the biodiversity of mutualistic ecosystems.

Pertumbuhan dan Mortalitas Ikan Kuro (Eleutheronema tetradactylum) yang Didaratkan di Pelabuhan Perikanan Nusantara Kabupaten Merauke

This research aimed to determine the size structure, length-weight relationship, growth, and mortality of kuro fish (Eleutheronema tetradactylum) that landed on Nusantara Fishery Harbour, Merauke District. The samples were taken off in August-October 2022 at Nusantara Fishery Harbour, Merauke District. The metusedsing was a purposive sampling method. The measured data was the total length and weight body of kuro fish. The size structure and length-weight relationship of kuro fish were analyzed using Microsoft Excel. Meanwhile, the growth and mortality were analyzed using the FISAT II application. The result analysis shows that the range of E. tetradactylum total length landed on Nusantara Fishery Harbour is 430 – 1030 mm with a weight range of 92 – 3613 grams. The length-weight relationship of E. tetradactylum has the allometric negative growth pattern with equation W = 0,0016L2,1167 in August, W = 0,0017L2,1134 in September, and W = 0,0017L2,1077 in October. The analysis of E. tetradactylum’s growth parameter shows the value L∞ = 1053 mm, K = 0,51/year, and t₀ = -0,1201 year. The result mortality analysis of E. tetradactylum shows the total mortality (Z) was 0,78/ year, natural mortality was 0,43/year, fishing mortality (F) was 0,35/year, and exploitation rate was 0,45/year.

Nonnative Smallmouth Bass in the Snake River, Idaho: Population Dynamics, Demographics, and Management Options

Abstract The Snake River in Idaho, USA, supports a popular sport fishery for nonnative Smallmouth Bass Micropterus dolomieu, but there are limited studies on the population dynamics of this introduced species in Idaho and other water systems in the western United States. The purpose of this study was to describe the population dynamics and demographics of Smallmouth Bass in the Snake River, Idaho. In total, we sampled 4,929 Smallmouth Bass during electrofishing surveys on the Snake River (separated into nine segments) and three major tributaries (Boise, Payette, and Weiser rivers). We estimated age for 1,869 Smallmouth Bass sampled from the Snake River (n = 1,433) and three tributaries (n = 436). Catch-per-unit-effort for all nine segments combined on the Snake River was 36.6 fish/h (±4.4 SE). In the tributaries, catch-per-unit-effort varied from 43.6 to 125.0 fish/h. Relative weight of all Smallmouth Bass varied from 86 to 107, indicating that fish were in relatively good body condition. Fish in the system grew fast, with relative growth index values often near or exceeding 100 for all age classes. Total annual mortality for the Snake River was 45.1 ± 0.7%, and it was 36.8–40.5% in the tributaries. Furthermore, we estimated exploitation to be 5.3% (90% CI; ±2.2%) for the Snake River and tributaries combined. We used a yield-per-recruit population model to evaluate the effects of varying minimum length limits on the fishery. With the observed population demographics and exploitation rates, increasing the current minimum length limit from 305 mm to 356 or 406 mm would probably have little influence on the number of Smallmouth Bass available to anglers. However, increasing the length limit would result in reduced biomass available for harvest. The potential for recruitment overfishing was minimal for all minimum length limits and levels of exploitation. As such, changes to current harvest regulations do not appear warranted. Our findings provide important information on the population dynamics of Smallmouth Bass that can be useful in evaluating their management across Idaho and in similar systems in western North America.

Hybrid Salp Swarm and Improved Whale Optimization Algorithm‐based clustering scheme for improving network lifespan in wireless sensor networks

SummaryWireless sensor networks (WSNs) represent the collection of restricted energy sensor nodes that are deployed in an area of target for gathering potential environment data for decision‐making with respect to their objective of application. However, the implementation of energy‐effective data gathering strategies in large‐scale WSNs is the most challenging due to the limited energy resources. Clustering‐based data gathering strategies are identified to be quite effective for energy saving that directly attributes to extended network lifetime. Moreover, optimal path amid the cluster head (CH) and sink node needs to be selected for sustaining energy efficiency and improving network lifespan. In this article, Hybrid Salp Swarm and Improved Whale Optimization Algorithm (HSSIWOA)‐based clustering scheme is proposed for improving the network lifetime and routing optimization with maximized energy efficacy. It integrated the exploration capability of Salp Swarm Optimization Algorithm (SSOA) with exploitation benefits of Improved Whale Optimization Algorithm (IWOA) for balancing the trade‐off between the rate of exploration and exploitation during CH selection process. It utilized the parameters of residual energy, load balance, intra‐cluster distance, inter‐cluster distance, and node centrality into account during the process of fitness evaluation. It performed well by constructing an optimized number of clusters, such that energy stability and network lifetime are maintained in the network. The experimental results of the proposed HSSIWOA scheme confirmed extended network lifetime of 21.64%, minimized energy utilization of 23.42%, and maximized throughput of 18.56%, better than the baseline approaches.

Population dynamics of Blood Cockles (Anadara granosa) in the coastal waters of Letman Village, Kei Kecil District, Southeast Maluku Regency

AbstractThe waters of Letman Village, Southeast Maluku Regency are clam fishing grounds which is a source of income for fishermen. One of the shellfish caught is the Blood Cockle (Anadara granosa). The purpose of this study was to analyse and examine the stock of A. granosa clams in Letman village, Kei Kecil District, Southeast Maluku Regency (length and weight frequency) and to determine the mortality rate and exploitation rate of Blood Cockles. This study was conducted between January and June 2022 with a sampling time of once a month for six consecutive months. Random sampling method was used through a free collection at low tide. The total sample collected during the study was 741 individuals. The research data were analysed using FiSAT II program version 3. The smallest size of the sample obtained during the study was 30 mm and the largest was 69 mm. The infinity length (L∞) is 78.50 mm, the growth coefficient (K) is 0.8/year, and the theoretical lifespan of Blood Cockles at a length equal to zero is −0.514/year. Analysis of the total mortality rate (Z) of Blood Cockles (A. granosa) was calculated at 3.90/year with a natural mortality rate (M) of 1.22/year and catchment mortality (F) of 2.68/year, while exploitation rate (E) was at 0.69/year. The addition of new individuals (recruitment) took place every month with varying numbers and the highest recruitment occurred in July and October while the level of exploitation of Blood Cockle in the waters of Letman Village was considered high (overfishing).

Ecological dynamics and conservation implications of Indo-Pacific Tarpon (Megalops cyprinoides) in Lake Siombak, North Sumatra, Indonesia

This study presents a comprehensive examination of the Indo-Pacific Tarpon (IPT) population in Lake Siombak, North Sumatra Province, Indonesia. Through a year-long investigation, we analyzed various facets of IPT ecology, encompassing population structure, growth dynamics, reproductive behavior, feeding habits, and mortality parameters. Male dominance in collected specimens, coupled with consistently immature gonads in females, suggests a unique reproductive pattern influenced by the brackish nature of Lake Siombak. Utilizing the von Bertalanffy method, we determined a moderate growth rate in IPT, with a predominance of medium-sized, sexually immature individuals. The dietary analysis revealed an omnivorous nature, with a notable reliance on zooplankton, particularly Cladocera and Copepods. However, the most significant concern arises from the estimation of the exploitation rate (E), surpassing the annual optimum exploitation threshold, indicating a state of overexploitation. This underscores the urgent need for regulatory measures to ensure the sustainability of IPT resources in Lake Siombak. Our findings contribute to a nuanced understanding of IPT ecology in this specific ecosystem, emphasizing the importance of balanced conservation and management practices. The documented reproductive, growth, and feeding patterns provide crucial insights for informing targeted conservation strategies and safeguarding the enduring viability of the IPT population in Lake Siombak. This research serves as a foundational contribution to the broader field of fisheries science, advocating for evidence-based management to preserve the ecological balance of aquatic ecosystems.

Body length changes for Atlantic salmon (Salmo salar) over five decades exhibit weak spatial synchrony over a broad latitudinal gradient.

Understanding the factors that drive spatial synchrony among populations or species is important for management and recovery of populations. The range-wide declines in Atlantic salmon (Salmo salar) populations may be the result of broad-scale changes in the marine environment. Salmon undergo rapid growth in the ocean; therefore changing marine conditions may affect body size and fecundity estimates used to evaluate whether stock reference points are met. Using a dataset that spanned five decades, 172,268 individuals, and 19 rivers throughout Eastern Canada, we investigated the occurrence of spatial synchrony in changes in the body size of returning wild adult Atlantic salmon. Body size was then related to conditions in the marine environment (i.e., climate indices, thermal habitat availability, food availability, density-dependence, and fisheries exploitation rates) that may act on all populations during the ocean feeding phase of their life cycle. Body size increased during the 1980s and 1990s for salmon that returned to rivers after one (1SW) or two winters at sea (2SW); however, significant changes were only observed for 1SW and/or 2SW in some mid-latitude and northern rivers (10/13 rivers with 10 of more years of data during these decades) and not in southern rivers (0/2), suggesting weak spatial synchrony across Eastern Canada. For 1SW salmon in nine rivers, body size was longer when fisheries exploitation rates were lower. For 2SW salmon, body size was longer when suitable thermal habitat was more abundant (significant for 3/8 rivers) and the Atlantic Multidecadal Oscillation was higher (i.e., warmer sea surface temperatures; significant for 4/8 rivers). Overall, the weak spatial synchrony and variable effects of covariates on body size across rivers suggest that changes in Atlantic salmon body size may not be solely driven by shared conditions in the marine environment. Regardless, body size changes may have consequences for population management and recovery through the relationship between size and fecundity.

Biology, Population Parameters, and Ecology of the Sergestid Shrimp Acetes intermedius in Damilisan, Miagao, Iloilo, the Philippines

This study investigated the biology, population parameters, and ecology of the sergestid shrimp (Acetes) in Barangay Damilisan, Miagao, Iloilo, the Philippines, by collecting samples for biological analyses and analyses using FiSAT II software. Based on morphometric evaluation, the sergestid shrimps present in the study site were identified as Acetes intermedius. Mature and near-spawning of the 180 specimens examined for ovarian maturity were > 50% in January, February, and April 2022. Size at sexual maturity was recorded at lengths ranging from 21.90– 23.10 mm. The highest mean TL and CL were 20.49 ± 1.84 and 5.32 ± 0.56 mm, respectively, in January 2022. The length-frequency data showed that the highest frequency was 18.50–20.40 mm. The male-to-female sex ratio was 1:2; wherein females dominated the males. The highest frequency for females ranged from 20.50–22.40 mm (TL). Estimated population parameters of A. intermedius were L∞ = 30.98 mm, K = 1.900 yr–1, Ø’ = 3.26 yr–1, tmax= 1.6 yr–1, M = 3.93 yr–1, F = 4.07 yr–1, Z = 8.00 yr–1, E = 0.51, E0.1 = 0.517, E0.5 = 0.349, Emax = 0.691, L₅₀%/Lc = 13.45 mm, and L₇₅% = 14.57 mm with a unimodal type of recruitment pattern. The value obtained for the exploitation rate was above 0.5, hence suggesting that the Acetes stocks in Brgy. Damilisan faced overexploitation. These results provide information that can be used to properly conserve, utilize, and manage the Acetes fishery industry in Miagao, Iloilo, the Philippines. Keyword.