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A die-off of native and exotic fish and invertebrate species, including the endangered southern steelhead trout (Oncorhynchus mykiss) was observed in Malibu Creek, Los Angeles County, during the summer and fall of 2006. Death was preceded by a period of illness during which trout in particular exhibited a noticeable yellow coloration. Physical, chemical and biological variables, including temperature, dissolved oxygen, a variety of chemical contaminants, presence of toxin producing algae, and direct pathology were examined but results remain inconclusive. The first day of a 12-day high temperature event occurred on the same date yellow trout were first observed. This sustained event is different from shorter term temperature spikes recorded in other years. Recovery monitoring documented re-colonization by all exotic fish species and crayfish, but limited numbers of southern steelhead trout in 2007. Surveys in summer 2008 documented a record number of anadromous adults (five silvery fish over 50 cm total length) and young of the year (over 2,200 under 10 cm).
California Sheephead, Semicossyphus pulcher, is a monandric protogynous hermaphrodite and a commercially and recreationally valuable labrid. Gonadal functionality of Sheephead through sex change was reclassified into nine classes using current criteria for categorization. Female ovaries were classified as immature, early maturing, mature, and regressing/recovering classes. Transition from female to male and subsequent male development was divided into early, mid and late transitional, developing/active male and regressing/recovering male. Reproductive states in Sheephead were correlated with estradiol (E2) and 11-keto testosterone (11-KT) concentrations in the blood plasma. All sexes had low E2 concentrations in the fall /winter seasons; in transitional and male individuals, levels remained low throughout the year. In contrast, female E2 concentrations were elevated in spring and peaked in the summer. Concentrations of 11-KT were variable throughout the year; however, females had significantly lower levels in the summer. This study allows a better understanding of the current state of California Sheephead in a heavily fished area. Knowledge of a species' reproductive characteristics is important in evaluating the sustainability of a population as it can set a baseline for reproductive potential. This research takes a critical step in gathering and organizing reproductive data such that it may be used in future studies for comparing reproductive potential across the range of the California sheephead.
In the southwestern United States giant reed, Arundo donax, is a non-native invasive plant that has become widely established in moist places and forms its largest stands along riparian corridors. The most widely reported negative effects include competition with native species, increased rate of transpiration, increased potential for wildfires, and stream channel and bank alteration. However, little is known about the faunal communities associated with this plant and the potential effects on native fauna. In this study, we focused our efforts on determining the faunal composition specifically from rhizome clumps of A. donax from a site located along the Santa Margarita River in San Diego County, California. A total of 2590 individual macro-invertebrates were collected and identified, and represented 64 species from 7 classes. No sensitive species and few vertebrates were found to be in association with A. donax rhizome clumps. Four non-native invertebrate species made up 43% of the total number of captured invertebrates, and 31% of the sampled invertebrates were confirmed as native species. This study demonstrates that A. donax rhizome clumps, and the soils associated with them, provide habitat for several native macro-invertebrate species, but can be dominated by a greater abundance of non-native species.
A morphometric comparison was performed on specimens of blue catfish (Ictalurus furcatus) from northern (Lower Río Bravo) and southern (Chiapas) México in order to identify diagnostic characters that allow their discrimination. The discriminant function analysis determined three characters to be highly diagnostic to separate the two groups of specimens: the southern group [SG] has a shorter anal base (mean = 3.4 times in standard length [SL], range = 3.1 to 3.7) vs northern group [NG] (mean = 2.9 times in SL, range = 2.7 to 3.1), a lesser head width (mean = 6.0 times in SL, range 5.1 to 6.8) vs NG (mean = 5.6 times, range = 5.3 to 6.0), and a lower number of anal rays (mean = 26, range = 24 to 28) vs NG (mean = 31, range = 29 to 34). Additionally, 14 other characters were also different (P < 0.01) between both groups. All these characters support the taxonomic validation of Ictalurus meridionalis (Günther 1864) for the individuals of SG that are currently included in I. furcatus Lesueur. Studies on comparative osteology and molecular genetics of both forms are needed for the clarification of their taxonomic status.