Occurrence of an exceptional catch of pelagic juvenile lingcod (Ophiodon elongatus) off Point Reyes, California

An exceptionally large catch of pelagic juvenile lingcod (Ophiodon elongatus) was made just offshore of Point Reyes, California in 1990. Results of 678 midwater trawls from annual surveys from 1983 to 1990 show that pelagic juvenile lingcod have a strong nearshore distribution and were most abundant in the Gulf of the Farallones, with a mean abundance of 5.0 per trawl. Otoliths from fish taken in the large catch were used to estimate parameters of a log-transformed Gompertz growth model, which was then used to calculate hatch dates. Hatching peaked around 24 March and ranged from 10 March to 19 April, implying a January-February spawning season for lingcod off central California. The large catch was associated with an anticyc-lonic eddy which would lead to water being trapped near the coast; convergence of fish associated with the eddy may have been due to either physical or biological effects.     

Growth Linkages and Urban Development in Niger

ABSTRACT. It is increasingly recognized that the assumption that the supply of tradable output is perfectly elastic, which underlies many regional economic models (esp. economic base models), does not hold in many developing countries. When the supply of tradable output (primarily agricultural products) and, in many cases, non-tradable output is inelastic, the resulting income multipliers will be substantially reduced. Recent calls for the promotion of market towns and smaller urban centers have not fully considered the impact of supply in elasticities on the capacity of such measures to stimulate broad-based development. This study uses data collected from firms in several market-town systems in Niger to examine the probable consequences. The paper argues that such policies are unlikely to be effective in countries like Niger where the vulnerability of the rural economy has severely limited the elasticity of the supply response, especially for agriculture and nonfarm production by small-scale producers.     

Vacancy Dynamics and Labor Market Efficiency in the Dutch Labor Market

ABSTRACT This paper focuses on cyclical and regional variations in vacancy dynamics in labor markets with persistent imbalances between demand and supply. In particular the so-called matching approach is used to investigate labor market efficiency across regions and over the business cycle. In this matching approach the relationship between the flow of filled vacancies and regional stocks of unemployed job seekers and vacant jobs is specified in a “search production” function. The matching approach is applied to the Dutch labor market, which is characterized by strong disequilibria and persistent regional differences in unemployment and vacancy rates. To explore the development of these regional imbalances from a demand side perspective, the dynamic structure of regional data on vacancies is analyzed over the business cycle. The movements of vacancy duration and the change in the vacancy stock over time appear to be similar across Dutch regions. Moreover, an investigation of the structural causes of regional variations in vacancy duration via shift-share analysis makes clear that regional differences in sectoral composition of unfilled vacancies do not contribute to regional differences in vacancy duration in the period 1989–93. Estimation results of a matching model reveal that there are no region-specific differences in labor market efficiency to produce filled vacancies. The ratio of vacancies to unemployment appears to be the critical determinant of the matching process in the Dutch regions. Another general (non region-specific) finding is that the estimated labor market efficiency increases during recessionary and recovery periods while it decreases during an economic boom.     

IMAGING FEATURES OF ATLANTO-OCCIPITAL OVERLAPPING IN DOGS

The imaging features of four dogs with atlanto-occipital overlapping are described. This malformation appeared to play a role in the development of neck pain, ataxia, variable cerebellar involvement, medullary kinking, and possibly syringomyelia. Using cervical radiographs, three of the four dogs were initially diagnosed with an atlanto-axial malformation. Because this disorder could not account for all clinical signs, magnetic resonance and computed tomography images were also acquired. These provided a more complete evaluation of the craniocervical junction, allowing detection of atlanto-occipital overlapping, medullary kinking, occipital dysplasia, abnormalities of the dens, and syringomyelia in these dogs. Head position during imaging affected the degree of atlanto-occipital overlap. These findings emphasize the need to modify the currently accepted imaging recommendations for dogs with head and neck pain and/or cranial cervical myelopathy. We suggest that the entire craniocervical junction be evaluated, even if atlanto-axial subluxation has already been detected. Moreover, we propose that atlanto-occipital overlapping is a perhaps underrecognized disorder that can influence the clinical signs and therapeutic outcome of dogs with anomalies of the craniocervical junction.     

Chemonucleolysis with Collagenase A Radiographic and Pathologic Study in Dogs

Collagenase, a proteolytic enzyme, was injected intradiscally in nine clinically normal, middle-aged beagles. Calcium chloride diluent solution (control), 100 ABC units of collagenase, and 250 ABC units of collagenase, were injected in randomly selected intervertebral discs (T13-L1 to L5-L6). On day 11, the discs injected with collagenase were narrowed radiographically, but there was no significant change in myelograms. Grossly and histologically, there was dissolution of the intervertebral discs, mainly nucleus pulposus, and protrusion of nucleus material in the vertebral body through bony end-plates in discs injected with collagenase. Collagenase chemonucleolysis may be an alternative to spinal surgery for intervertebral disc protrusion in dogs.