Homing and site fidelity in the greasy grouper Epinephelus tauvina (Serranidae) within a marine protected area in coastal Kenya

Homing ability and site-fidelity in the greasy grouper Epinephelus tauvina (Serranidae) were studied at Malindi Marine Park (6.3 km2), coastal Kenya, from January to April 2002 using acoustic telemetry. Displacement experiments involving 12 groupers (mean size 57.9 cm) from multiple capture sites resulted in a 67% homing success. Upon release at displacement sites (0.5 to 2.6 km from the point of capture), most initial movements were small-scale and non-directional. Neither the tidal range nor time of day influenced the magnitude of these daily movements. Returns to the capture sites were sudden, occurring predominantly (88%) on spring tide dates. Fish displaced at the spring tide returned to capture sites faster (8.6 d) than those displaced at the neap tide (14.3 d). Time taken to return to capture sites ranged from 4 to 19 d (mean 9.6 d) and was not correlated with distance of displacement. However, time taken for the fish to home was negatively correlated with tidal range at displacement. Home ranges established after homing (0.07 to 0.73 km2) were stable and negatively correlated with fish size, suggesting an ontogenetic shift in home range development

Analysis of fish catch data from 1985 to 1994 in the Kenyan inshore marine waters

Fish landing data collected by the Kenyan Fisheries Department from the nearshort coastal marine waters from 1985 to 1994 were statistically analyzed to determine trends in the traditional fisher's catch. Over the ten year period a significant decline occurred for total catch and for catches of seven commercially important fish families: Lethrinidae, Siganidae. Lutjanidae, Scaridae, Carangidae, Scombridae and Mullidae. 1994 registercd the lowest catch over ten years. The total catch for all the fish declined from a mean annual catch of 6150 metric tonnes in the 1980's to a mean of 5141 metric tonnes in the 1990's with the catch for 1986 being 2 times higher than that of 1994. Although Mombasa district had the highest mean annual landing, its total landings like that of Lamu and Kwale districts decreased over the years. However, Kilifi district showed a steady increase in catches over the years. The changes in fish landings is thought to be caused by lack of appropriate fishing regulations, leading to overfishing of the lagoonal reefs beyond their maximum sustainable yields

Experimental evaluation of influence of FADs on community structure and fisheries in coastal Kenya

Fish aggregating devices (FADs) have been widely used by commercial fisheries to increase the catchability of pelagic stocks in the open sea. FADs have the potential to enhance nearshore small-scale fisheries where stocks are often overfished. This study examined changes in catch composition, abundance, catch and effort, and aspects of diversity in Kenya's nearshore coastal fisheries after deployment of anchored fish aggregating devices (AFADs). The study combined both fishery independent and dependent methods in assessing changes in fish assemblages post-deployment. Results showed orders of magnitude increase in length, weight, commercial value, and catch per unit effort (CPUE) of landed catch after deployment of FADs suggesting that FADs had a positive effect on the local fishery. Species richness at FAD sites increased post-deployment (n = 281) compared to pre-deployment values (n = 223). Simultaneous use of several complementary structural indices may be required in order to accurately describe and monitor fish assemblages around the FADs. The findings suggest that AFADs are capable of creating both short and long-term impacts on livelihoods, with the potential to deflect pressure on the overfished nearshore fish stocks. However, more research will be needed on redistribution of fish around FADs, design and placement configuration, and site selection amongst others

Genetic diversity and population structure of the African catfish, <i>Clarias gariepinus</i> (Burchell, 1822) in Kenya: implication for conservation and aquaculture

African catfish, Clarias gariepinus, is an important species in aquaculture and fisheries in Kenya. Mitochondrial D-loop control region was used to determine genetic variation and population structure in samples of C. gariepinus from 10 sites including five natural populations (Lakes Victoria (LVG), Kanyaboli (LKG), Turkana (LTA), Baringo (LBA) and Jipe (LJP), and five farms (Sangoro Aquaculture Center (SAN), Sagana Aquaculture Centre (SAG), University of Eldoret Fish Farm (UoE), Kibos Fish Farm (KIB), and Wakhungu Fish Farm (WKU)) in Kenya. Similarly, samples from eight localities (four natural populations: LVG/LKG, LTA, LBA, and four farmed: SAN, SAG, KIB, UoE) were genotyped using six microsatellite DNA loci. For the D-loop control region, samples from natural sites exhibited higher numbers of haplotypes and haplotype diversities compared to farmed samples, and 88.2% of haplotypes were private. All except LJP and LTA shared haplotypes, and the highest number of shared haplotypes (8) was detected in KIB. The 68 haplotypes we found in 268 individuals grouped into five phylogenetic clades: LVG/LKG, LTA, LBA, LJP and SAG. Haplotypes of farmed C. gariepinus mostly have haplotypes typical of LVG/LKG, and some shared haplotypes of the LBA population. Microsatellite analysis showed farmed samples have higher numbers of alleles than natural samples, but higher observed and expected heterozygosity levels were found in samples of natural populations. Fifteen pair-wise comparisons had significantly different FST values. All samples were in Hardy-Weinberg equilibrium. Samples from the eight localities grouped into four genetic clusters (LVG/LKG, LTA, LBA and SAG), indicating genetically distinct populations, which should be considered for aquaculture and conservation

A novel marine bioinvasion vector: Ichthyochory, live passage through fish

Many species of Indo-Pacific holobenthic foraminifera have been introduced and successfully established sustainable populations in the Mediterranean Sea over the past few decades. However, known natural and anthropogenic vectors do not explain how these species were introduced long distances from their origin. We present evidence for a novel marine bioinvasion vector explaining this long-distance transport and introduction using both contemporary field and historical analyses. In 2015–2016, we found living specimens of 29 foraminiferal species in the fecal pellets of two Red Sea herbivorous rabbitfish—Siganus rivulatus and Siganus luridus in the Mediterranean. In our historical analysis, we found 34 foraminiferal species in preserved Red Sea rabbitfish specimens, dating between 1967 and 1975. In addition, we found congruent propagation patterns of the non-indigenous rabbitfish and foraminifera, lagging 4–11 yrs between discoveries, respectively. Predation of marine benthos by non-indigenous fish, followed by incomplete digestion and defecation of viable individuals, comprise the main introduction vector of these organisms into novel environments

Testing a global standard for quantifying species recovery and assessing conservation impact

Recognizing the imperative to evaluate species recovery and conservation impact, in 2012 the International Union for Conservation of Nature (IUCN) called for development of a “Green List of Species” (now the IUCN Green Status of Species). A draft Green Status framework for assessing species’ progress toward recovery, published in 2018, proposed 2 separate but interlinked components: a standardized method (i.e., measurement against benchmarks of species’ viability, functionality, and preimpact distribution) to determine current species recovery status (herein species recovery score) and application of that method to estimate past and potential future impacts of conservation based on 4 metrics (conservation legacy, conservation dependence, conservation gain, and recovery potential). We tested the framework with 181 species representing diverse taxa, life histories, biomes, and IUCN Red List categories (extinction risk). Based on the observed distribution of species’ recovery scores, we propose the following species recovery categories: fully recovered, slightly depleted, moderately depleted, largely depleted, critically depleted, extinct in the wild, and indeterminate. Fifty-nine percent of tested species were considered largely or critically depleted. Although there was a negative relationship between extinction risk and species recovery score, variation was considerable. Some species in lower risk categories were assessed as farther from recovery than those at higher risk. This emphasizes that species recovery is conceptually different from extinction risk and reinforces the utility of the IUCN Green Status of Species to more fully understand species conservation status. Although extinction risk did not predict conservation legacy, conservation dependence, or conservation gain, it was positively correlated with recovery potential. Only 1.7% of tested species were categorized as zero across all 4 of these conservation impact metrics, indicating that conservation has, or will, play a role in improving or maintaining species status for the vast majority of these species. Based on our results, we devised an updated assessment framework that introduces the option of using a dynamic baseline to assess future impacts of conservation over the short term to avoid misleading results which were generated in a small number of cases, and redefines short term as 10 years to better align with conservation planning. These changes are reflected in the IUCN Green Status of Species Standard

Testing a global standard for quantifying species recovery and assessing conservation impact.

Recognizing the imperative to evaluate species recovery and conservation impact, in 2012 the International Union for Conservation of Nature (IUCN) called for development of a "Green List of Species" (now the IUCN Green Status of Species). A draft Green Status framework for assessing species' progress toward recovery, published in 2018, proposed 2 separate but interlinked components: a standardized method (i.e., measurement against benchmarks of species' viability, functionality, and preimpact distribution) to determine current species recovery status (herein species recovery score) and application of that method to estimate past and potential future impacts of conservation based on 4 metrics (conservation legacy, conservation dependence, conservation gain, and recovery potential). We tested the framework with 181 species representing diverse taxa, life histories, biomes, and IUCN Red List categories (extinction risk). Based on the observed distribution of species' recovery scores, we propose the following species recovery categories: fully recovered, slightly depleted, moderately depleted, largely depleted, critically depleted, extinct in the wild, and indeterminate. Fifty-nine percent of tested species were considered largely or critically depleted. Although there was a negative relationship between extinction risk and species recovery score, variation was considerable. Some species in lower risk categories were assessed as farther from recovery than those at higher risk. This emphasizes that species recovery is conceptually different from extinction risk and reinforces the utility of the IUCN Green Status of Species to more fully understand species conservation status. Although extinction risk did not predict conservation legacy, conservation dependence, or conservation gain, it was positively correlated with recovery potential. Only 1.7% of tested species were categorized as zero across all 4 of these conservation impact metrics, indicating that conservation has, or will, play a role in improving or maintaining species status for the vast majority of these species. Based on our results, we devised an updated assessment framework that introduces the option of using a dynamic baseline to assess future impacts of conservation over the short term to avoid misleading results which were generated in a small number of cases, and redefines short term as 10 years to better align with conservation planning. These changes are reflected in the IUCN Green Status of Species Standard

Marine reserves and their influence on adjacent fisheries in coastal Kenya

Analysis of more than two decades (1978 to 2001) of commercial fish catch data collected by the Kenya Fisheries Department indicates that a rapid overall decline in landings occurred in coastal Kenya during the last decade. The decline was most severe in the most populated Mombasa district. Amongst the commercial families, the groupers (family Serranidae) showed the steepest decline in landings and forecasts indicated a gradual decline in yields for the next decade (2002-2011). This thesis reports on the results of experiments to test the efficacy of two of the oldest marine parks in Kenya (Malindi, 6.3 km² and Watamu, 10 km², created in 1968) to restore such over-fished stocks and their potential to sustain adjacent sites through a spillover effect. A comparison of catch per unit effort (CPUE) and sizes of fish species across the park boundaries showed that species are orders of magnitude more abundant and larger inside the parks than the adjacent fished sites. However, higher seasonal abundance and even larger sizes of some species (e.g., the whitespotted rabbitfish, Siganus sutor and the seagrass parrotfish, Leptoscarus vaigensis) occur outside the parks (especially at Watamu). Results suggest that yields of some species in adjacent fished sites and perhaps beyond may have been sustained by a spillover effect from the parks. However, this effect appears to be species and site specific and affected by season and reef types. Size frequency distribution of commercial species showed a high proportion of small sized fish inside the parks, suggesting the parks additionally function as nursery grounds. -- A logistic decay model fit to species abundance (CPUE and #/500m²) data across the park boundaries showed steep gradients of fish abundance (especially for the sky emperor, Lethrinus mahsena) across a patch reef at Malindi, indicating limited dispersal across this reef type. However, the locally abundant whitespotted rabbitfish, Siganus sutor, had a shallow gradient of abundance across this reef indicating ability for dispersal. Inter-annual variations in patterns of abundance were evident. For example, S. sutor was more abundant outside Malindi Park during the SE monsoon of 200/2001 but was more abundant during the NE monsoon in 2001/2002. -- Tagging experiments showed higher spillover rates of commercial species, mostly of S. sutor and the emperors along fringing reefs at Malindi and Watamu Parks. Little spillover was suggested off the patch reef at Malindi. Most of tagged fish showed little out-migration from the parks and had multiple recaptures within the parks. Large-scale (30-180 km) movements were reported in three species (Gaterin flavomaculatus, S. sutor and L. mahsena) that were generally believed to be sedentary on home reefs. -- Reduction of fishing mortality within the parks may interact with species behavior to enhance conservation potential of the parks. For example, results of acoustic telemetry studies within Malindi Park, showed site fidelity and homing tendency in a commercial grouper (Epinephelus tauvina: Serranidae) displaced to multiple sites (0.5-2.6 km) within the park. Homing in this species is thought to be linked to tidal factors amongst others and to play a role in the preservation of spawning stock biomass within the parks. -- Estimates of demographic parameters (growth, mortality and survival rates) of some commercial reef fishes necessary for stock assessment and management are provided. These rates are largely unknown for most species, thus making cross-regional comparisons difficult. However, where data exist for other geographical areas, growth parameters (e.g., instantaneous annual growth rate, K, and absolute growth rates) were higher, especially for Siganus sutor and Lethrinus mahsena, on the Kenyan coast suggesting superior conditions for growth. -- The overall implication of these results to species conservation, and the function and design of marine parks are discussed in the thesis